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XX-932AC-35

September 1975

191 pages

Original

32MB

Document:	102737607-05-19-acc
Order Number:	XX-932AC-35
Revision:	0
Pages:	191
Original Filename:	102737607-05-19-acc.pdf

OCR Text

SOFTWARE
SOFTWARE
Languages

AID
ALGOL

APl
BASIC

COBOL
ISAM

ePl
FORTRAN
FORTRAN Version 4
MACRO

System Utilities
SOAT
Data Base Management
System
ITPS-l0
UNK-l0
MACY11-LNKX11

SYSTEM ARCHITECTURE
The DECaYltem·1090
Central Processors
Instruction Set
InstructIOn Groups
Instruchon Formal
Trap Handling on the
K110 and KIlO
Processor Modes
Fast Register Blocks
Real-Time Clocks
Memory

Cache Memory
Memory Systems
Interleavmg
Input/Output
Prlonty Interrupt System
Multiplexed 1/0 Bus
Massbus
110 Channel Capacity
Console/ Diagnostic Computer
System Integrity Features
Power Fall
Error Handling
Multiprocessor Systems
Dual CPU System

2
4
6
6
6

7
8
9
9
10
12
12
12
13
13
13

,.,.

15
16
16
16
17
17

PERIPHERALS
PERIPHERALS

Disk Systems
DAS33 Buffered Data Channel
DECtape Transport
Magnetic Tape Systems
Hard Copy Equ ipment
Card Reader.
Line Print.rs
Terminals

20
22
23
24
26
26
26
28

DDT
FAILSAFE/BACKUP
Message Control System

PIP

DATA COMMUNICATIONS
DATA COMMUNICATIONS
33
System Concepts
34
Asynchronous Communications 34
Synchronous Communications 34
Synchronous vs. Asynchronous
Transmission
35
Remote Communications
36
Netwo", Concepts
37
Simple Topologies
37
Complex Topologies
37
Task-to-Task Communication
38
IBM Device Emulation
and Termination
38
CommunJcatkms Products
3.
DN87/87S Universal
Synchronous/Asynchronous
Front End Subsystem
39
Complex Topologies
'2
DECneHO
.2
DAS80 Series Aemote Slalion
.3
DAS92 Remote Station
'5
DAS 61 IBM 2780/3780 Support 46
DAS 621BM HASP Multi-leaving
Support
'6

CONFIGURATOR
47

CONFIGURATDR
1

RUNOFF
TECD
Operating System
TOPS-10 Operating System
Command Control Language
File System
Input/Output
Memory Management
Multi'Processor Systems
Inter-job Communication
Communications Software
Multlmode Computing
Timesharing
GALAXY-10 Batch
Real-Time Computing
Diagnostic Software
High Availability
Maintenance Features
On-Une Diagnosis

59
61
60
60
60
62
61
62
62
63
63
64

65
65
65
66
66

67
67
67
68
68
68
68

••

69
72
73
76
76
77
78
78
79
79
79
81
.3
83
83
83

SERVICES
SERVICES

People
Parts
Support
Service Agreements
Education
Logistics
Technical Documentation
Software Services
Advanced Systems Group

87
87
87
88
86
8.
6.
90

The DECsyslem-1090 is an extension
of the DECsystem -1080 which was announced in September of 1974 and first
delivered in June of 1975. The DECsystem-1090 offers all the outstanding
features of the 1060 plus many new
ones. The key features of the DECsystem-lOoo are:
The new Kll0B Processor.
It features 1.4 mips, integrated channels, cache memory and a PDP-11 Can·
sale front end computer which permits
on-line, remote diagnosis and maintenance. The new CPU permits more
compact configuration and lower power
consumption through the use of integrated channels ; improved performance; and substantially lower system
purchase and maintenance costs. Single
and dual CPU systems, featuring high
availability, are offered .
The new MH10 Memory System.
It offers 256K 36-bit words in one 31·
system cabinet. Internal 2-way interleaving and eight memory ports accom modate up to 2 CPU 's and all of
DIGITAL's standard memory channel
peripheral subsystems. The DECsystem-IO memory can be expanded with
up to 16 MH10 units to over 4 million
words or 20 million ASCII characters.

320K (rU70) and 780K (TU72) characters per second allow DECsystem-l 090
users 10 select the tape system which
meets their needs. With the new TUn
system, 6250 bpi capability has been
added to our product offerings allhe
high end and the TTUt6 72KHz syslem
greatly reduces the cost of 1600 bpi
capability, for low performance requirements.

The recently-announced RP06 200
megabyte Disks.
They are now available using the
integrated MASSeUS· controllers. Not
only is the cost of Disk System s substantially reduced, but the use of integrated controllers and channels provide
automatic update of the cache memory
-thus reducing overhead. The on-line
disk data storage can now be extended
to over 6.2 billion ASCII characters or
about 5 billion a-bit bytes.

A compfete range of Una Printen
and Card Readers.
The new lPl00 offers high quality
M band ~ prinling a11200 10 1500 lines per
minute. The LPlO and LU10 offer high
quality mid-range and Iow-speed printers
at lower cost 10 meet users' individual
needs. The CR10Eand CR10F 1200and
300 card per minute readers offer a
choice of two excellent card readers.

The new TTU16 Magnetic Tape
Subsystem.
It now uses the integrated MASSeUS·
Controllers to extend the DECsystem1090 tape capability to three subsystems. Transfer rates of 72K (lUI6),

The new ON87S CommunlcaUons
front end.
It provides additional features and
lower costs than previous communication front end offerings. Cost is reduced
through the use of the integrated DTE
channels which utilize high-speed microcode for data transfer. Important new
features include DECnet compatibility
and simultaneous support of synchronous and asynchronous communica·
tions on a single front end. All the standard ANF features are also supported.
Up to three DN87S units per 1090 System
can accommodate up to 336 full duplex
asynchronous lines or 36synchronous
lines. The number of lines can be extended by adding a ONB7A and up to
three DN87D s, each of which can support 112 asynchronous or 12 synchronous lines.

UNIT
RECORO
MEMORY B S

M HIO

MEMORY
256 1C TO 4M
WOi!OS

110 BUS
0
M

ICLIO

n u 16

DN87S

TAPE
SYSTEM

SYSTEM

A DECsystem-1090 Block Diagram

~~~J

I OTE

I
RTP04/6
DISIC
SYSTEM

TAPE
SYSTEM

INTERNAL CHANNELS
AND CONTROLLERS
MASS&uS

TU70ln

0
I

a:JMM

Within the family of six DECsystem10 configurations, there are three central processor units. All operate under
the same DECsystem-l00perating system (TOPS-tO), execute the same software, and share most models of DECsystem-l0 peripheral equipment. The
three processors differ in their speed,
method of address mapping, memory
capacity, program size, auto-diagnostic
and restart features, and priority interrupt system.
The KA10 central processor is used
in the DECsystem-l050 and 1055. The
more powerful KilO central processor
is used in the DECsystem-l070 and
1077 configurations. The top-of-theline KL10 central processor is used in
the DECsystem-tQ80, 1090 and 1099.
The high speed 2K word cache memory
(K=1,024) permits rapid instruction execution while minimizing accesses to
main memory. A double precision floating multiply, for instance, executes in
4.BJlsec.

Because ali processors operate wIth
the same operating system, it is easy
to field upgrade a system with a KA10
and replace it with a KI10 processor;
or take a system with a KI10and replace
it with a KL10 processsor, providing a
significant increase in the computing
power with no necessary changes in
user programs.
The 1090 configuration differs from
the 1050 or 1070 in that the high speed
data channels and communications
processor channels are integral to the
central processor. Up to eight high speed
buffered data channels can be utilized
which support DIGITAL's Massbus.
peripherals. Because the data chan nels
access four 36-bit words of memory in
one channel request cycle the total
throughput is in excess of one million
words per second or 4 megabytes per
second. Fornon-Massbus. peripherals,
external channels which transfer directly to memory can be utilized. An important feature of the integrated high
speed data channels is that cache
memory is automatically updated
4

during 110 transfers. The integrated
front end processor channels will accommodate up to three PDP-11 communications front ends in addItIOn to
Ihe KL 10 console front end. These
channels utilize high speed microcode
to transfer and process data comrng
from the PDP-ll communications fronl
ends. All channel data transfers are
parity checked. A final benefit of the
1090 internal channels is configuration
simplicity, improved maintainability
and reduced power consumption.

DECsystem-l0 at a Glance.
1040/1050
Relallve Performance

1.0

1055*

1060/1070

1.8

2.2

30-80

1088*/1099*

1077*

1080/1090

3.5
40-100

4.8
50-127

75-150

6.7

Avg Number of Users

10-40

20-70

No ofCPUs

Memory Size In K words
(min -max .) (K &'024)

64-256

128·256

128-4096

128·4096

128-4096

No. ollnslruchons

366

378

398

Instruction Look-ahead

No
No

Yes

Virtual Memory

No
No

Yes

Memory Interleaving

20r4way

2or 4way

20r4way

2or 4way

2or4way

15 each

4x15

4x15each 8 x 15

Index Registers

CPU

Accumulators

16 each

4 x 16

CPU

Instruction Times (microseconds) "
Fixed Point Add

2or4way

8 x 15 each

CPU

4xl6each 8 x 16

8 x 16 each

CPU

2.8

1.6

.52

Fixed POint Multiply

9.8

4.6

2.4

Unconditional Jump

1.5

1. 1

1.1

.36

Single Precision
Floallng POint Add

9.8

2.7

1.8

Double PrecISion
Floallng POint Add

59.4

3.9

2.2

Double PrecISion
Floallng Muiliply

N.A.

8. 1

4.8

Double PrecISion
Floating DIvide

16.0

10_2

10.2

NA
NA

N.A.

5.6

1.4

1.6

.48

110 Bus Band width
(words/second)

200K

370K

Memory Bus Band width
(words/second)

4000K

Increment and Move Byte
Move from Memory

- Dual-processor systems execute two Instructions simultaneously.
*'For 108011088 and 1090/1099 Operands in Cache Memory.

Instruction Set
InstrucUon GrOtJPB
The KA 10 has 366 instructions, the
KI10 378 instructions, and the KL 10398
instructions, an extremely large reper-

toire which provides the flexibility required for specialized computing problems. The instruction sets of the KA 10
and KilO are hardwired. By contrast,
the instruction sel of the KL10 is microprogrammed; thai is, each instruction
is actually a series of miera-instructions
that perform various logical functions

such as processor state control, data
path control and actual implementation
of each instruction in the KL10's set. The
micro-code is loaded into a lK BO-bi!
word RAM (random access memory)
through the PDP-!! console/diagnostic

computer. Since the set provides so
many instructions to choose from, fewer
instructions are required to perform a
given function. Assembly language programs are therefore shorter than with
other computers, and the instruction
set simplifies the Monitor, language
processors, and utility programs. For
example, compiled programs on a
DECsystem-1Q are otten 30 to 50 percent shorter, require less memory and
execute faster than those of comparable
computers.
In addition to these instructions, the
DECsystem'10 provides 64 programmable operators, 33 of which ~trap ~ to
the Monitor (Monitor calls) and 31 of
which trap to the user's call area. The
remaining instruction codes areunimplemented and reserved for future expansion. An attempt to execute one of these
unimplemented instrUctions results in
a trap to the Monitor.
The instruction set, despite its size, is
easy to learn. It is logically grouped into
families of instructions and the mnemonic code is constructed modularly.
All instructions are capable of directly
addressing a full 256K (36 bit) words
of memory without resorting to base
registers, displacement addressing, or
indirect addressing. Instructions may,
however, use indirect addressing with
indexing to any level. Most instruction
classes, including floating paint, allow
immediate mode addressing, where
the result of the effective address calculation is used direclly as an operand
in order to save storage and speed
execution.

Instruction Format
In all the non";npuvoutput instructions,
the nine high-order bits (o-S) specify
the operation, and bits 9-12 usually address an accumulator but are sometimes used for special control purposes,
such as addressing flags. The rest of the
instruction word always supplies information for calculating the effective
address, which is used for immediate
mode data or is the actual address used
to fetch the operand or alter program
flow. Bit 13 specifies the type of ad.
dressing (direct or indirect), bits 14-17
specify an index register for use in ad·
dress modification (zero indicates no

indeXing), and the remaining eighteen
bits (18-35) contain a memory address.
The instruction codes that are 001
assigned as specific instrucbons are
performed by the processor as so-caJed
Munimplemented operations M
, as are
the codes for floating point and byte
manipulation In any KA 10 that does not
have the hardware fO( these instructions.
An inpuVoutput instruction is deslg'
nated by three 1s In bits 0-2. Bits 3-9
address the inpuVoulput device to be
used in executing the instructIOn, and
bits 10-12 specify the operation. The rest
of the word is the same as In other
instructions.

AOOII£SS T"I?[

-...~

-T~l"
.. II

o
INSTRUCTION FORMAT

HALF-WORD DATA TRANSMISSION
The half-word data transmission instructIOns move a half-word and may
modify the contents of the other half of
the destination location. There are 16
instructions which differ in the direction
that they move the chosen half-word
and in the manner in which they modify
the other half of the destination location.
FULL-WORD DATA TRANSMISSION
The full-word data transmission instructions move one or more full words
of data from one place to another. The
Instructions may perform minor arithmetic operations such as forming the
negallve or the magnitude of the word
bemg processed
BYTE MANIPULATION
The five byte manipulation instrucbans pack Of unpack bytes of any length
anywhere within a word .
LOGIC INSTRUCTIONS
The logic instructions provide the
capabilities of shifting and rotating, as
well as performing the complete set of
16 Boolean functions on two variables.
FIXED·POINT ARITHMETIC
Two common conventions are to re gard a number as an integer (binary
point at the right) or as a proper fraction
(binary point at the left) : in these two
cases, the range of numbers represented by a Single word Is - 2311 to 2311
- lor - I to 1-2.315. Since multiplication
and division make use of double-preciSIOn numbers, there are special lnstructlons for performing these operations
to yiekj results that can be represented
by a single word
The format for double-length fixed poent numbers is just an extension of the
Single-precision format. The magnitude
(or Its twos complement) is the 70-bit
stnng '" bits 1-35 of the high- and loworder words Bit 0 of the hlgh-order
word IS the sign, 0 for pOSItive, 1 for
negallve Bit 0 of the low-order word is
ignored The range for double-length
integer and proper fractions is thus
- 210 to 210 -lor -I to 1-2-10. Zero is
represented by a word containing aliOs.

FLOATING-POINT ARITHMETIC
All DECsystem-l0 processors have
instructions to perform scaling, negating,
addition, subtraction, multiplication and
division upon numbers in Single-preCi sion, floating point format. In the singleprecision floating point format, one bit
is reserved for the sign, eight bits are
used for the exponent and 27 bits are
used for the fraction.
As a superset of the KAIO, the KilO
and KL10 have instructions to perform
all of the above functions in doublepreCision floating-point format as well
as single-preCiSion floating-paint. In
double-precision floating-paint format,
one bit is used for the sign. eight bits are
used for the exponent and 62 bits are
used for the fraction.
FIXED/FLOATING CONVERSIONS
Special KilO and KLIO instructions
provide the capability of converting
fixed-point formats to or from floatingpoint form ats. Two sets of instructions
are provided to perform this function :
one set optimized for FORTRAN and a
second set optimized for ALGOl.
ARITHMETIC TESTING
The arithmetic testing instructions
may jump or skip. depending on the
result of an arithmetic test and may
first perform an arithmetic operation
on the test word.
LOGICAL TESTING, MODIFICATION,
AND SKIP
These instructions modify and/or test
using a mask andlor skip on selected
bits in an accumulator.
PROGRAM CONTROL
Program control instructions include
several types of jump instructions and
the subroutine control PUSHJ and
POPJ instructions.
INPUT/OUTPUT OPERATIONS
Input/output instructions govern all
direct transfers of data to and from the
peripheral equipment and also perform
many operations within the processor.
Block transfer instructions handle bulk
data transfers to and from 110 devices.
UNIMPLEMENTED USER
OPERATIONS (UUOs)
Many of the codes not assigned as
specific instructions are executed as
unimplemented user operations wherein
the word given as an instruction is
trapped and must be interpreted by a
routine included for this purpose either
by the programmer or by the Monitor.
Those UUOs reserved for use by the
Monitor are called Monitor UUOs
(MUUOs), while user UUOs are called
Local UUOs (LUUOs). lnstructions that
are illegal in user mode also trap in the
same manner as MUUOs.
7

BUSINESS INSTRUCTION SET
Five instructions comprise the Business Instruction Set in the KLIOcentral
processor. Four of these are new arithmetic instructions to add, subtract, multiply, and divide using double precision,
fixed-point operands. The new STRING
instruction is capable of performing
nine separate functions.
These functions include an EDIT
capability: decimal to binary and binary
to decimal conversion in both offset
and translated mode, (offset mode is
byte modification by addition of the
effective address of the string instruction. This also occurs in EDIT. In addition
to providing the translation function,
those instructions which use translation
can control the flags in ACs and can
detect special characters in the source
string.); Move String in both offset and
translated mode: and Compare String
in both offset and translated mode.
This Business Instruction Set provides
faster processing since there are specific instructions for doing more comprehensive string operations. These
instructions can be used on a variety of
code types such as ASCII and EBCDIC.
TrapHandlingon the KilO and KL1 0
The KilO and KLIO provide facilities
for handling arithmetic overflow and
underflow conditions. pushdown list
overflow conditions, and page failures
directly by the execution of programmed
trap instructions. This trap capability
avoids recourse to the program interrupt
system.

If a program is running in a public
submode, pages within the user's addressing space are accessible only if
they are listed in the user's page map
and are defined to be accessible from
public mode. Pages designated public
are, by definition, accessible. Pages
designated concealed may be accessed
only at defined entry pOints. i.e. portals
which permit entry from public submode
programs. In concealed submode operations. programs can access all of
the virtual addressing space. However,
if a program runn ing in concealed submode executes an instruction from an
area designated to be public, the state
of the processor transfers over into
public submode. Concealed areas can
be used for proprietary coding that can
be executed but not altered or examined
by users in the public mode.
The supervisor and kernal submodes
are similar but not identical to the public
and concealed submodes. Supervisor
submode programs can access but

cannot atter areas designated as concealed. Also. any instruction executed
out of a public area from either supervisor or kernel submode returns the
processor to supervisor submode. In
kernel submode operations all of memory is accessible and can be altered.
Programs operating in kernel submode
can address portions of memorydireclly,
without paging. and it is through the
kernel submode program that page
restrictions are established. Functions
delegated to supervisor submode generally include those affecting IndIVidual
users as opposed to overall system
management of mput/output, pnOflIy
interrupts. page map accounting. elc.
which are handled by kernel submode
programs. The ability of kernel submode
programs to supply InformatlOfl which
supervISOr submode programs can read
but not alter allows portions of Ihe oper.
atmg system to be hardware-protected
from other portions undergoing ffiOdt.
fica lions or design changes.

Processor Modes
Instructions on the KAtO are executed
in one of two modes depending upon
whether a mode bit has been set.
Programs operate in either User Mode
or Executive Mode. In Executive Mode
operations, aU implemented instructions
are legal, addresses are nol relocated,
and all core locations are accessible.
The Monitor operates in Executive
Mode and is able to control all system

resources and the state of the processor.
In User Mode operations, addresses
are relocated, certain instructions are
illegal, causing monitor traps when
executed, and address references are
confined within two user program
segments.
The KilO and KL10 further divide
Executive and User Mode operation
into two submodes each. User Mode
is subdivided into public and concealed
submodes and Executive Mode into
supervisor and kernel submodes. For
each 512-word page in the system,
information is stored in a table maintained by the operating system which
specifies whether or not a page can be
accessed or altered, and if it is defined
to be public or concealed.

KI10 AND KLI0 PROCESSOR MODES

USER MODE
Public Submode
• User programs
• 256K word address
• AU instructions permitted
unless they compromise
integrity of system or other
users
• Can transfer to concealed
submode only at entry points

Concealed Submode
• Proprietary programs
• Can READ, WRITE,
EXECUTE or TRANSFER
to any location
labeled Public

EXECUTIVE MODE
(Monttor,
Supervisor Submode
• Performs general management of system
• Performs Ihose functions
that affect only one user
at a time
• Executes in virtual address
space labeled public

•

Kernel Submode
• Performs 110 for system
• Performs those functions
that affect all users

Real-time Clocks

Fast Register
Blocks
General-purpose registers are a DECsystem-tO feature that help improve

program execution. These sets of fast
in tegrated circulI registers can be used
as accumulators, index registers, and as
memory locations Since they may be

addressed as memory loeations, they
do not require special Instructions.
One set of 16 registers IS Included in
the KAID, four sets of 16 fa st registers
are Included In the KilO. and eight sets
of 16 fast registers are Included In the
Kll0 Context sWitching on the KAIO is
performed by stormg the regis ter Informallon mto core lOCations. Program
sWitching time l or the Kll0 between
register slacks IS 500 nanoseconds
On the KilO and KL 10. different regrster blocks can be used l or the operating
system and IndlYldual users This eliminates the need for stOring regi ster contents when sWitching tram User Mode
to Executive Mode _Also, a critical real time program IS able to maintain its own
register block for handling data and
Interrupt sequences at maximum speed.

The OKtO Real-time Clock is available
with each KAtD- or KilO-based DECsystem-tO and provides high-resolution
timekeeping for time accounting, timebase maintenance, periodic high-fre quency interrupts, and interval timing .
Meeting the most demanding real -lime
requirements, the clock provides 10
~sec resolution and a choice of up to
2111 possible liming intervals, so that interrupts can be programmed at intervals from to ~sec up to 2.6 seconds.
In addition to an interval register, the
OKlO has a frequency counter which
counts the pulses of an internal 100 kHz
± O.OI clock, or an external clock having
a maximum frequency of 400 kHz. The
clock includes a comparator network
which provides a running comparison
between the frequency counter and
the internal register. When the frequency
counter reading equals the to tal on the
internal register, a program interrupt is
generated and the frequen cy counter
is automatically reset so that it can time
the next interval.
The clock, which is assignable to any
interrupt channel. can be used to pace
real -time, monitor, or other functi ons
performed in either Executive or User
Modes. In fact, a KA 10 or KilO system
can have two clocks-one for each
mode-since two device codes are
available for ctock use. Clock updating
is interlocked with the DATAl instructions so that it can be read correctlyat any time-by the KA to or KilO without
losing a clock pulse.
9

The four clocks built into the KL10
provide a number of timing and counting func tions including an interval timer.
a time base, an accounting meter and
a performance analysis counter.
All of the operations on these clocks
are accomplished by means of 110 instructions to internal devices. Many of
these functions use a microsecond
source of pulses which is counted down
from the basic machine clock. The
0.005% tolerance will give less than
five seconds drift over 24 hours.
The Interval Timer provides a programmable source of interrupts with a
I microsecond resolution and is similar
to the OKlO real-timectock.1t is used for
real -time appli.:.:ations and for page
management by the Monitor. It is designed so that a real-time deadline
schedule with varying deadlines can be
implemented.
The TIme Base provides a 6O-bit microsecond resolution source of elapsed
time. This gives over a 9,140 year maximum time before wrap-around.
The Accounting Meters provide an
accurate and reproducible measure of
the amount of processor resource used
by a job, interrupts, page failures, and
cache activity_
The Performance Analysis Counter
provides a tool for studying hardware
and software performance of the system. lt may be used to point to hardware
and/or software bottlenecks.

On the KA10, dual memory protection
and relocation registers protect other
users and the monitor from errors in the
active user program. If a user attempts
to reference memory outside his area,
his program is stopped from operating
and control is transmitted to the operating system. The feature also permits
dynamic memory allocation, allowing
each user program to be assigned either
one or two segments of memory. One
of these segments can be write-protected so as to protect critical programs
or data from errors committed by the
user. Segments-which are multiples or
t024 words-may be located anywhere
in memory and may contract and expand as needs dictate. Memory management techniques, employed by the
Monitor, insure efficient memory usage.
The division of programs into two segments also makes possible the reentrant
or recursive use of language processors
and systems programs. With the DECsystem-tO, all DIGITAL-supported language processors and most utility programs are reentrant. In other words, each
program is written in two parts. One part
contains pure or reentrant code that is
not modified during execution so the
same copy can be used to simUltaneously service any number of USers. A
separate second part of the program
belongs strictly to each user and consists of non-reentrant code and data.
This section is stored in a separate area
of core. This feature allows more users
to utilize a given amount of physical
core simultaneously. Alternatively, less
core is required to service a given number of users. The result is much more
efficient use of computing resources.
The ability to divide programs into
two segments is not limited to DIGITAlsupplied language processors and
utilities. User-written programs, including those written in higher-level languages such as FORTRAN and COBOL,
can also take advantage of this feature.
Thus, user developed applications can
benefit from the same efficient treatment given DIGITAL-supplied software.

KI10 Processor
Associative Memory
£F~(tTIV( &IICJIIIUS

•

•
~{ "-,

•

~,~

I~(

I I •

• I

I "

KilO ASSOCIATIVE MEMORY

KL10 Processor
Page Addressing
L • I • I

•

"
,-,
I

I
"

•

• I

KLlO PAGE ADDRESSING

The KilO and KlIO provide memory
address mapping from the program's
memory address space (referred to as
the ellecllve address) to the physical
memory address space by substitution
of the mosl Significant bits of the memory
address ThIs mappmg provIdes access
to the enttre physical memory space
whICh can be up to 16 tImes larger than
the ma)umum user address space. The
user's effective address space is 256K
words addressed wIth IS-bIt addresses:
the phYSIcal address space is 4.096K
words addressed wIth 22-bit addresses
(where 4.096K IS equIValent to 4,194,304
doornail
The memory mapping process utilizes the most sIgnificant 9 bits of the
effective address as an Index Into the
appropria te page map (User or ExecutIVe) . Thedala located by Iheindex provides 13 blls whIch are appended to the
least-significant 9 bIts of the effective
address m order to form the 22-bit
physical address Also provided are 3
bits whICh IndICate what type of memory
requests are allowed to the page In
QuestIOn (none, read-only. proprietary,
elc.)
If this scheme were implemented
exactly as outlined abOve. every user
memory reference would reqUIre two
actual memory references one to
obtain the memory mappmg data and
one to obtain the user's mapped memory reference In order to reduce the
number of actual memory references
to nearly the same number as required
by Ihe program, an assoda live memory
mappIng unillS used In the KilO, while a
copy of Ihe entIre page table is kept in
the K110 hardware

If the address is in the rang e 0-17
(oclal) inclusive, the hardware fast
register blocks are referenced instead
of the memory system. On the KilO, the
User Mode bit and the high·ord er 9-bits
of the virtual address are compared
against the contents of the associative
memory registers which are part of the
memory mapping hardware. These 10bits will either exactly match one of the
associative registers or a no-match
occurs. On the KL10, the User Mode bit
and the high-order 9-bits of the virtual
address are used todo a "table look·up"
in the hardware page table.
On the KilO. if a match exists, the
contents of the related register supply
the 13-bit most-Significant portion of
the physical memory address and also
supply 3 bits which indicate what type
of memory references are allowed to
this page, i.e., if the memory request is
not consistent with the request type
allowed bits, a page failure occurs. On
the KL10, if a page table entry exists, the
contents of the entry supply the 13-bit
most-significant portion of the physical
memory address and also supply 3 bits
which indicate what types of memory
references are allowed to this page.
For both the KilO and KL10. if the
memory request is consistent with the
request type allowed bits, the physical
address used consists of the 13 bits
from the related register as the most
significant bits of the physical address
and the 9 least significant bits of the
effective address as the least significant
bils of the physical address.
When the relocation data for a refer·
enced page does not exist in the associ·
ative memory of the KilO. or the hardware
page table of the KL10 (i.e., a no-match),
the hardware reads the relocation data
from the page table in memory and
stores it into the associative memory
of the KilO or the hardware page table
of the KUO.
The associative memory in the KilO
has associated with it a reload counter
that points to one of the 32 entries in
the memory.
11

Any time a word of the associative
memory of the KIlO is referenced and
the reload counter is pointing at it, the
reload counter is incremented to point
at the next word in the KilO associative
memory. Whenever it is necessary to
load a new entry into the associative
memory, the location repla ced is the
one to which the reload counter points.
Thus, at worst, a page which was just
referenced would not have its word in
the KilO associative memory replaced
by the next memory reference. If a
particular word in the KIlO associative
memory has not been referenced in
some time, the reload counter would
be left pointing to this word, having been
pushed away from all words in associative memory which have been used.
Thus, a ,-bit approximation to "feastrecentIY'used" page table operation is
obtained.
The monitor assigns the core area
for each user by loading the various
page tables, setting up the trap locations
in the user page map, and responding
appropriately when a trap occurs. The
Monitor provides memory protection
for itself and each user by filling the
page tables only with those entries
which are allowed to be accessed. A
zero access bit in the page table will
cause a reference to the associated
page to initiate a page failure trap to
the Monitor.
The TOPS-l0 Operating System
utilizes the KIlO and KL10 in-core page
maps to create one or two segment
pf"Ograms in roughly the same fashion
as it uses the protection and relocation
registers of the KA 10. Themajorbenefits
of the paging capability are a smaller
unit of core allocation (512 words instead or 1024), the freedom to scatter
the pages of a segment randomly
through physical core (avoiding core
fragmentation and the overhead of
repacking core), and the opportunity
to execute a program when all of its
pages are not in physical core (I.e., a
virtual memory capability).

Memory Systems

Cache Memory
The KL10 features a cache or buffer
memory with 160 nanosecond access
time. Data being written to or read from
memory is typically found in the cache
85 to 90 percent of the time, thus giving

the Kll0 an effective memory access
time of 334 nanoseconds with current
DECsystem-l0 memories. Another
feature of the Mstate-of-the·art~ design
cache memory on the Kl10 is that it
does nol require write-through to memory. This eliminates, for example. the
necessity of writing back into main

memory each value of an index in a loop
comprised of only a few instructions.
A cache sweep feature allows all
pa~es or one selected physical page in
main memory to be updated from the
cache.

To meet the requirements of large
systems, DECsystem-l0 core memory
can be modularly expanded to 256K
wordsforKA10-basedsystemsor4.096K
words for Kll0- and KL10-based systems. all directly addressable. Memory
can consist of combinations in 64K.
128K and 256K word modules. The
structure of the memory bus gives the
central processor and high-speed data
channels simultaneous access to separate memory modules and allows
each to operate at its own speed.
The MF10 provides up to 4 ports and
the MG10 or MH10 up to 8 ports. Each
port can be further expanded through the
use of the MX10 memory multiplexer.
The multiplexer handles up to eight
channels, inter-leaving data from the
channels on a word-by-word priority
basis. Such parallel operation yields
many improvements over systems
which provide only a single path to
memory. The memory bus station allows each data channel to transmit full
36-bit words in parallel at a speed of
one million words per second. In total.
the memory structure operates at rates
of up to 10 million characters per second
when 1/0 devices and processors are
concurrently simultaneously transferring data. In addition. the memory bus is
capable of handling a max imum of 16
memory modules. Eachmemory module
provides switches which allow that particular module to represent any module
of its size in the addressable memory
space. Thus, one model can replace
another without rewiring. The Switches
also provide for memory Interleaving.
The core memory systems available
for the DECsystem-l0 are described in
the memory table below.

Interleaving
The concept of interleaving has long
been used to Increase the effectrve
bandWidth of DECsystem' lO systems.
On KA- and KI-based systems, successive memory locations were Iocared
via memory addressing hardware, I~
alternating memory modules. Thus.the
processor, when requesting successive
logicallocalions, would nothavelo wall
for the complete memory read/write
cycle to be complete before affectmga
fetch. The tirst memory module could
be completing the wrrte cycle, while the
second memory module could be ac·
complishing a read cycle.
The memory Implementation
niques for the Kl dramatically extend
this conc,-,pt. The memory bus architecture of the Kll0 differs from both
the KAKl and the KIlO In that rtsWldth lS
tour 36-bit words. That is, in an adequately configured memory system.
the Kll0 actually reads or wntes four
words concurrently from memory. The
fout logically successive memory Ioca·
tions (obtained from four physlCaly
separate memory modules) are placed
m the KL's cache memory, and In
typical programs. another COfe memory
reference need not be inJtlated untd!he
four mstructions or data have been
processed. Combined wIth the typical
effects of the cache memory, therefore
the KL has an effectIVe memory word
access time of 334 nanoseconds, using
current DIGITAL memory.

teen·

Cor. Memories
Word Sole
M,nlfnum Memory 5I.!:e
Maxlf!lum Memory SIZe

KAm
KilO
KLIO

M HIO

MGIO

"'~

36 boIS plus panty

36 bob plus PiI"~

J6 0tU pIIA pwIIy

32'

320<

.,-,

' 096K
'096K

Module St.les
321( wo rds
641< words
1281< words
256K words
Read Access Time

V"
V"
V,.

TyDtCaI

7J5

MaxlfTlum
Cycle Time
Interleaving
Minimum memo ry
that can be disabled

V"
V,.
V,.
No

620 ns

"'"
,.,,'
102.1<;

Va
Va
No
No

660M

550M
610nl

10, I
2ol .way

950M
201, .. il1

32'

1 24eC
2or.w,y

""""
""""

Ext&rJI.r 0",,"

Priority
Interrupt System
The DECsystem-l0 Priority Interrupt
System IS one of the most flexible
avaIlable today. Oevices are assigned
under program control to anyone of
seven pnonty levels through the dynamIC Ioadmg of 8 3·bit regIster w ithin
the devICe Each Interrupt level has any
number of high-speed programmable
sublevels Thus, a program can change
the priOrity level of any device or disconnect the deVice hom the system
and later reinstate it at any o ther level.
In the same manner, a program can set.
enable, or disable, all or any combinahon of levels with a single instruction.
In addition, the program can assign

some or all devices to the same level.
A set of instructions (block-in and
bIOCk-oU!) allow blocks o f Information
10 be transferred between a device and
memory with a single instruc tion.These
Instructions identify the source o f the
Interrupt. update a word count and data
address, transmit or receive the block
or Informabon. and dismiss the Interrupt
The system can also generat e interrupts through software Real-tIme hardware can thus operate on a high -priority
level while related computations, particularly If they are length y, can be performed on a }ower level
The DECsystem -1O program-assignable ptlonty Interrupt system prOVides
much greater flelubillty than permanenUy hard-wifed systems Hard-wifed
systems reqUire a large number of
levels, often operate wi th an extremely
high overhead, and canno t change dev.ce ptlorilles without system shutdown
and rewlflng

Multiplexed

1/0 Bus

An interrupt on the Ki lO or KL10 can
cause the processor and the interrupting
device t o immediately initiate one of
several possible actions. In response to
the "interrupt grant" signal from the
processor, the device may supply a
33-bit word which is decoded as 18 bits
address, 12 bits data, 3 bits fun ction.
The processor then does one of the
following:
• Executes the instruction found at the
supplied 18-bit address (KI100rKl1O)
• Transfers a word into or out of the
addressed location (KItO or KL 10)
• Adds a signed 1,-bit (12 bits+ + II bits)
value to the addressed location
(KL10 only)
• Traps to a predefined memory location (KAIO)
Peripheral devices which are not
equipped with the decoding logic perform an interrupt and transfer of control,
as on the KA 10, to one of the standard
mterrupt trap locations.

The DECsystem-IO Multiplexed I/O
Bus provides a 36-bit full word parallel
path between memory and an 1/0 device for purposes of control or low-speed
data transfer. To initiate high speed data
transmission directly between memory
and a device connected to the memory
bus, a control word is first transferred
over the 110 bus to the buffer of the
high-speed device controiler. Then, on
command, entire data blecks are moved
directly to orfrom memory with a single
instruction. (For a description of the
memory bus, see the discussion of
Memory Systems.)
The I/O bus may also be used as a
control and data path to/from a large
number of tow-speed liD devices. Transfer is performed in 36-bi! words in
parallel at speeds of 200K words/sec
on the KA 10, and 370K words/sec on
the Kll0and KL10. Thus each data transmission instruction moves one word
of data between memory and the buffer
of the device controller. When block
input or output instructions are used,
entire blocks of data are moved to or
from the device with a single instruction.

10.40 1070 loao MASS8US CHANNEl
AJiJ a:NrROl BlOCK DIAGRAM

:=
Massbus
The KL10 architecture and implementation now allow use of DIGITAL's
lalest Massbus controllers, channels,
and peripheral devices. Although, via
mem ory bus and 110 bus logic, the KL10
supports traditional peripheral control
units, the effi cient memory control unit
provides paths and logic for transfers
into and out of DECsystem-1090 memory. Virtual-ta-physical address translation is p erform ed by a 64 x 154-bit
RAM. The memory control also includes
a series of multiple word channel
buffers for high-speed direct 110 over
the channel bus to the individual Massbus devices. For each device, there is
one RH20 channel containing a 16-word
data buffer, a channel command word
register, and a control word location
pOinter -effectively a program coun t er.
The channels perlorm data transf er by
executing channel programs which are
set up in memory by device service
routines.
A storage bus provides a 1.6 million
w ords/second transfer bandwidth between the memory control unit and
memory. In diagnostic mode, the storage bus is used to access the internal
memory controllers. The channel bu s
is a physically short, high-speed data
transfer path providing a peak 110 bandwidth of six million wordslsecond between the memory control unit and the
Massbus controllers. The channel bus
o perates in a synch ronous tim e division
multiplexed mode, allowing the connection of multiple controllers to
memory.
A high·speed data path (Mass bus)
connects the integrated channel controllers and mass storage devices, such
as disk or tape. Operating either asynchronously or synchronously, the
Massbus transfers control and status
information or blocks of data between
devices and controllers, The UNIBUS,
an integral part of the PDP-11 architecture, provides a data and status control
path between the Front End Processor
and the devices making up the PDP-"
system, including the commu nications
interlace and unit record 110 devices.

..
,r-------MX-IO
MEMORY
MULTIPLEXER ...1.,, ________

OfIO.DFIOC

MEMORY

QA5JJ

'H~

IF REOUIREO

1090 MASSSlIS CHANNEL

CENTRAl

PROCESSOR

OM'

'H20
uP TO a

I/OCHAMMEL
CAPACITY
DECsystem-l0SO and 1070 generation equipment implement high-speed
data transfers from mass storage devices via a direct to memory channel
using the DF10, DAS33 or DX10 channel
and an appropriate controller. If the
number of channels exceeds the available memory ports then an MXlO multiplexer can be used. In general. capacity
is determined by the memory system
word transfer rate capacity which will
vary based on the type of memory used
and the method of interleave. For current memories, four words can be transf erre d every microsecond in a four-way
interleaved configuration. Conflict in
memory port contention will reduce the
effective word transler rate somewhat
and can result in "overruns " which occur when a rotating mass storage device cannot execute a memory transfer
in the required time. TOPS-l0 recovers
from this situation and simply re tnes the
transfer until it is completed. The DAS33
buffered channel will greatly reduce o r
eliminate ·overrun" capacity loss.

The DECsystem-l090 can use either
the direct to memory channels or the
internal channels in the Kl10B Central
Processor. Since the processor is con·
figured on a lower memory pnorilyport
than direct to memory channels ther elS
no conflict between these devICes The
KL 10 cache and internal butfenng
further reduce any contention. The
number of internal high-speed channels which can be operated Slmul·
taneously depends on the data transfer
capacity between the CPU and Memory. This, in turn, is a function 01 the
memory Interleave method and corre·
sponding number of data bosses Illplemented. The follOWing table sum·
marizes this relationship based on
RP04 or RPOO device transfer rates.
Memory Interleave
and K110 Bus Mode

2151 6

Number of Channels
Translernng Simultaneously

This table presumes no ·overruns•
Should these occur they would be
handled by TOPS-lO In the same man·
ner as direct to memory channels It
should be noted that for typiCal data
transfer rates of under 1000 blocks per
second there IS no measurable confIICI
between instruction executIOn and 110
transler

One of the more significant features
of the KL10 is the PDP-11-based Con·
sole/Diagnostic Computer.
The POP' 11 communicates with the
KL10 through a DECsystem-l0/PDP-11
interface The interface allows data
transfers between the POP-II and the
KL10 to take place simultaneously. On
the POP' II side
the Interface, data
has dIrect memory access over the
PDP' lt UNIBUS in 8· or lG·bit bytes. On
the KLIO side of the interface, data may
eXISt In any size byte up to 36 bits in
length
The POP' 11 serves as the console device for the KL 10 processor and Includes
a TU56 DECtape for loading and diagnosing the PDP-It and back-up for the
RP04 which normally loads the KL10's
micro-code memory An LA36 DECwriter-II provides operator/monitor
communication
As a dtagnosUc computer. the POP-II
can examine the data paths and the
conttollogic of the KL to vIa a separate
dtagnostlc bus, even if the KL 10 is completely inoperatIve Other features of
the dIagnostIC computer allow all data
busses to be checked Remotediagnos,
IK: checIung over telephOne connection
can also be performed via the PDP-II
computer
The console/diagnostIC computer is
a Slale-ot-the-art concept 10 provIde
the DECsystem-l090 and DECsystem1099 With greatly improved mean'limebetween-faIlure and reduced meantlme'lo-repair The KLINIK diagnostic
system permits remote diagnosis of
system failures via the console/dIagnostIc computer

Power Fail
If system power fails, a power failure
detection circuit senses the condition
and causes an Interrupt The interrupt
can trigger the operation of a program
which saves all valuable registers so
that the system can be restarted in a
minimum amount of time.
On the KilO and Kll0 (through the
PDP-l1 console computer) an automatic restart capability has been added

to resume normal operations in the
event of a power outage. All three
phases of AC power are monitored.
Low voltage on any phase will initiate a
sequence of power-down operations.
A program-selectable automatic restart capability is provided to allow
resumption of operations when power
relurns. Alternatively, a manual restart
maybe used.
Temperature sensors strategically
placed within the equipment detect
high temperature and low air flow conditions and cause power shutdown.
This, in turn, initiates the power failure
interrupt.

Error Handling
The TOPS-tO Monitor records errors
that occur in the slave CPU (on a dual
CPU system) or peripheral subsystems
and notifies the operator If the error
can be corrected then users affected
simply continue running. Alternatively,
the operator may request that the faulty
device be detached 10 which case the
user job will be notified and contInued or
restarted as required. If the error detected is in memory then TOPS-10 wIll
attempt to move Its own data, if any,
out of the failing memory In the case
of disks, the system will attempt to
migrate any sWapping space to another
unit to prevent loss of jobs. TOPS-tO also
provides diagnostics to fa cilitate on-line
maintenance of a particular devIce concurrent with user mode operation .
16

Dual CPU System
Multiprocessor systems, built around
all 01 DIGITAL's current CPU's, offer
attractive. economical solutions needed
for capacity and availability
In these configurations. two processors divide responsibilities as master
and slave The master runs the TOPS-tO
operating system and handles all
scheduling and 110 One processor can
take over the other's role through the
use of strateglcaUy-placed bus SWitchIng hardware. which allows peripheral
deVICes to be under the con Irol of either
processor If the master malfuncllons.
the system stops and an operator can
have It back mto action 10 under five
minutes by reconflgurlng all 110 to the
slave, whICh then becomes the maSler
Users IUSI temporarily have somewhat
less computing power to work With, but
can stili gel thelf JObs done Mmutes
after a CPU malfunction that could
keep a Single system down for hours,
the dual processor configuratIOn can
be back In actIOn Redundant disks and
communcatlOns subsystems can
provide Increased capaclly while all
components are fully operational and
back-up 10 case an I$OOled controller
or subsyslem malfunction

An extremely important and valuable
side benefit of the redundant, switched
configuration is system maintainability.
Malfunctioning subsystems, (such as
disk controllers, etc.) which require a
CPU to fully diagnose, repair, and certify
as operational, may be included in a
-maintenance contigura tion ~ while the
remaining components of the system
conllnue with the production tasks.
Users need not sutter from any lack of
capability until scheduled main tenance
activity or -non-prime time" allows the
testing of the complete system. W hen
the subsystem or component is released,
fully tested, trom Field Service, a
scheduled recontiguration (providing
minimum impact on users) can be accomplished, providing full capability
again.
17

Dual CPU/peripheral configurations
can be initially installed or, through the
addition of appropriate redundant
system components and bus switching
hard ware, can provide attractive upgrade/migration paths for existing
systems.

SYSTEM

1099
A

K1108
FRON T

'NO
'H1O
OTE

* 'RP0416

l,-L=-.l
ON

8 7S COMMUNICATIONS LINES
ISYNC. AND ASYNC.)
MONITOR

MAGTAPE
SYSTEM

ON COMNUNICATIONS LINES
875 jSYNC AND ASYNC.)

......

ore

'H2O
",aNT

' NO

RECORD DEVICES
jSWITCHA8LE)
L--"':'~ID~''-J---_-:- UNIT
A

DUAL DECSYSTEM 1090 SYSTEM

r--=====r--~~~_r=~I/~O~'~U~S~#~':::r::~--A
LPT

fRONT

CDR

' ND
'H ~}----L-------r---.----~---r-

ON
875

COMMUNICATIONS LINES
ISYNC AND ASYNC.)

MONITOR

TAPE SYSTEM
IUSED 8Y 80TH CPU'S)

MCNnOR

LIN'

ON
875

COMMUNCATION LNES
jSYNC AND ASYNC)

ore
RH20
FRONT

'NO

l___~__-=~~-,~'~/O~8U~S~"~'~::J:::~_ ,
A

UNIT RECORD EQUIPMENT

There are four disk systems available
on the DECsystem-l0. The RHS04 system is designed to provide the DECsystem-l0 with a fast -access, high transfer
rate swapping system which greatly enhances system performance and load
handling capability. The DECsystem10's three disk pack systems offer rapid
access, on -line storage, and large capacities at low cost. Modularly expandable, a DECsystem-l0 allows up to four
controllers each with eig ht drives giving
a total capacity in excess of 6.3 billion
ASCII characters. In addition tostorage,
a disk system may be used as either the
primary or secondary swapping system.
The RTP06 is DIGITAL's newest disk
system. It operates through a controller
which transfers data directly to and
from memory via the KL10 internal
channels. Since the controller provides
overlapped positioner operation, the
TOPS-l0 operating system will simultaneously position two or more disk
drives, shortening the effective access
time and increasing throughput.
Each RP04 or RP06 drive configuration can have an optional dual Mass
Bus· channel connection which allows
access and data transfer via two paths
for each individual drive.
The RH04 and RP06 offer a high level
of data reliability. A phase locked loop
clock system and MFM (modified frequency modulation) recording provide
the latest in reliable reading and recording techniques. In addition, error detection and correction hardware provides
information as to the position and pattern of any error burst up to 11 bits within
the data field. Correction of any data
field errors is then accomplished under
TOPS-10 software control.

Disks

DISk Drive Capacity (m words)
Transfer Rale I/Js/word)
Access Time (msec)
Track-Io-track
Average
Maximum
Organizallon ,
words/seclor
sectors/track
tracks/cylinder
cylinders/pack
Number of Heads
Number of Recording Surfaces
Number of Disks
Number of OnvesfControlier
Number of OrivesfSystem
Maximum Slorage/System
(b ASCII Chrs)

RP03

RP04

RP06

RSo.

10.24

20.48

40.96

.256

5.6

4.0

7.5
30

7
28
50

10
28
55

0
8.5
8.5

128
20

128

411

"
815

"
12
"

128
10
20
400
20
20
11
8
32

1.96

64
64
64

19
12
8
32

8
32

1
1
8
16

3.19

6.30

.004

----------------------~c

The DAS33 is intended to replace
DF10 data channels in large DECsystem-10 configurations containing many
high-speed peripherals where memory
transfer throughout is a critical consideration in a peak memory contention
environment.

• Hardware and software compatible
with the standard Data Channels.
• 256-word data channel buffer reduces memory contention for highspeed, direct-Io-memory peripherals, increasing memory transfer
throughput.
• Control word and data word ~Iook'
ahead" logic
• 22-bit memory addressing (four
million words of 36-bit memory)

The DAS33 has been developed by
the Advanced Systems Group to reduce peak memory contenllon and to
increase memory transfer throughput
for the new generation of hIgh-speed
peripherals such as swapping disk
pack systems. It is fully hardware and
software compatible with the existing
data channels. By incorporating a 256word buffer (equivalent to two disk
sectors). block transfers are averaged
over available memory bandwidth. This
results in a minimization of memory
contention during peak memory trans fer and an increase in usable memory
transfer throughput for high -speed
peripherals. Throughput Is further enhanced by the ~Iook-ahead~ feature for
control and data words.

The DAS33 is recommended 104'
large DECsystem-10 configuraoons
havIng swapping and disk pack suit
systems. By minimizing memory contentIon (wIth the two-disk sectorbufferl
and by providing control and data w()f1(
"Iook-ahead~. the OAS33 will rocr~t:
the system memory throughpu
•
Its 22'
from these high-speed deviCeS.
bit-wide memory addressing but ~
abies JlD controllers to address up 0
four million (36-M) words of me~o~
The DAS33 includes its own 19'1OC
cabinet and memory bus cables. ~ne
OAS33 is needed for each contro er.

Digital Equipment Corporation's
popular computer data storage medium,
DECtape, is available in a duaHransport
verSIOn This fixed-address, bi-dlrecbonal magnetic tape storage system
provides random access for highspeed reading or Wrillng of files on 260
fOOl reels of ¥. -Inch-wlde magnetic
tape contained on a reetless than four
InChes In diameter Redundant record ing (each bit of data is recorded on two
separate tracks) assures high reliability
and eliminates the need for character
panty checIong. tn addloon, block check
summing Insures data Integflty
DECtape does not reqUire the rewind
and count record operations or the WrltIn9 of separate header records typical
of ordinary magnetic tapes The high
rehablhty and convenient size make
DECtape the ideal medium for program
storing and transportation

DIGITAL provides a complete range
of magnetic tape systems from the lowcost THU16 to the mid-range TU7QI
TU71, to the high-performance TU72.
The THU16 subsystem provides 200,
556,800 bpi (NRZI) and 1600 (Phase Encoded-PEl capability at low cost. With
a tape speed of 45 ips, these transports
exhibit a 12K character per second
maximum transfer speed. For systems
with moderate duty requirements, the
THU1 6 is an excellent price/performance choice.
The TU7D series of high-speed magnetic tape drives represents the lalest
state-of-the-art des ign in tape t ransport
technology.
The TU7a provides 800 bpi (NRZI)
and 1600 bpi (PE) capability at 200 ips,
resulting in a maximum transfer rate of
320K characters per second. The TU7l
provides 7 -track capability at 220/5561
800 bpi (NRZI) al200 ips for a maximum
transfer rate of lOOK characters per
second.
For very high performance systems
DIGITAL offers the TU72, providing
faster processing, fewer tapes, faster
dum ps, and improved error handling
for DEC-1O sites. This 6250 bpi drive
provides 3 to 1 recording density compression of an eq uivalent 1600 bpi drive.
Using the Group Coded Recording
(GCR) t~chnique the hig her density
provides more capacit y per tape,
higher data rates and b etter error
correction.

Magnetic Tape Systems
The TU7D-series drives incorporate
such features as automatic threading
and loading of 5-. Blt'.!- and lDlh-inch
reels as well as industry-standard cartridges. Dynamic amplitude control
during read operations improves performance during 1600 bpi operations by
reducing read /write errors, avoids the
need for preamplifier adjustments,
and allows optimum performance w ith
different tape brands on the same drive.
All TU7D tape drives are equipped with
an automatic reel hub to speed and
ease tape loading and alleviate reel slippage. An analog capstan control provides constant motor drive control during read/write and rewind for smoother
operation and greater drive-to drive
compatibility, while a velocity feedback
reel control provides for protection and
velocity sensing of the tape loop in the
vacuum columns to minimize reel overspeed; this prevents tape matching , results in longer tape file, and greater ma chine reliability. A linear high-speed rewind mechanism reduces rewind time
and lessens stress on the reel drive system resulting in smoother operation. A
tap e storage pocket is provided for convenience.

The controller handles up to 8 tape
drives and providesdlrectaccesstolhe
OECsystem -1D memory via an 1f'I~e
grated data channel. The controller 1'1eludes such features as Improved
phase-encoded and group coded recordmg error correctIOn technIQUes for
fewer permanent and temporary read
errors A read-only memory control for
mcorporalJon m microprogram dl&\lnos tiCS, monolithic MSI deSign, f~
greater reliability, loadable in-line mIcroprogram diagnost)cs, programmable maintenance memory, adjust·
ment-free read detection, and a radJ8:
interface which allows each indlvldua
drive to be maintained or physlC8l1y
removed without effecting the operation of other units.

I III fI!

TU7QITU72

Magnetic Tape

Tape Speed
Transfer Rate at
200 bpi
556 bpi
800 bpi
1600 bpi
6250 bpi
Recording Technique
Nominal Inter-record
Gap
9-track
7-track
Rewind Time (2400 ft)

TU70
200 ips

TU l 0W

TU 16

45 IPS

45 ips

9 K char/sec
25 K char/sec
36 K char/sec

9 K char/sec
25 K char/sec
36 K char/sec
72 K char/sec

160 K char/sec
320 K char/sec

NRZI

PE/NRZI

PElNRZI

06 inches

0.5 inches

0.6 inches

0.75 inches
195 seconds

3 min utes

45 seconds

TU71
200 ips

TU72
125 ips

40 K c har/sec
11 1.2 K c har/sec
160 K char/sec

NRZI

200 K char/sec
780 K char/sec
PE/GCR

0.3 inches
0.75 in ches
45 seco nds

55 seconds

Line Printers
Card Readers
Designed to meet varying throughput requ irements and provide quiet,
reliable trouble-free operation, the
CR10 card readers accept 8O-column
EJA-ANSI standard cards. For fast
throughput, the user can choose the
console model CRlO-E which pro-

cesses 1200 cards per minute or the
table model CR10-D which processes
1000 cards perminute. The CAtO-F card
reader is a lower-cost table model
which operates at 300 cards per minute,
but utilizes the same excellent features
as the high-throughput model.

The LPlO-F and lP1Q-H are drum type line printers deSigned with emphasis on output quality and operatmg reli ability. The two-speed capability of the
64-character LP1Q-F and the 96-char-

acter LP1D-H increases the printing
quality for both low-speed operation
and multi-part forms handling.
The LPlQ-F operates at 1250 or 925
lines per minute and the LP1Q-H al925
or 675 lines per minute. Both line printers
featu re optical vertical format unit using
12-channel tape, and a quick-change
drum whic h allows the character set to
be c hanged in just 5 minutes. Both
printers are available with either an EDP
or Scientific character set for the quickchange drum .

For user sites requiring high-grade
print quality, flexibIlity of pnnllng fonts.
heavy print volumes and high rebabllty
from a horizontal font-mobon linepnnlel,
DIGITAL offers the LP100. ThelP100,an
Impac t printer usmg a Chara band~
available w ith a 64-characterEDPctlaracter set font on one side of the band
and a 96 character seton the other The
Charaband· can be reversed by the
operator in about one minute. The
lPl00 stores a stream of uplO132 characters In a print line buffer and upon
command prints the contents of tne
buffer and advances the forms as
specified.
• "'rademark of Dataproducts CorporatiOn

Une Printers
PRINTERS

TYPE

LPlD-F
lP1o-H
LPlOO

impact
impact
impact

MAXIMUM
MAXIMUM
PRINT SET
COLUMN
" CHARACTERS SPEED
LINES/MINUTE WIDTH

96
64/96

1250/925
925/675
1200/900

132
132
132

PAPER

II PARTS

TYPE

OF PAPER
FORMS

std.
std.
std.

6
6
6

Each DECsystem-10 is capable of supporting up to 512 interactive terminals.
A wide variety of EIAand 20 mA Current
Loop compatible terminals is supported
by the DECsystem-l0.
The LA36 OECwriter II is designed to
be industry's lowest-priced, best performing, most reliable 3O-cps impact
teleprinter. DECwriter II is packed with
capability: it's fast-a true 3O-cps machine; it's qUiet-you'll almost forget it's
there; it has many people-oriented design considerations you wouldn't expect
in a cost-conscious product ; it's versatile -you can use 6-part forms and even
standard 132-column line printer paper;
and it's built for a long, reliable li'etime
of heavy use.

The LA35 Receive Only terminal is an
LA36 without the input key board_
The LA37 APl terminal is really three
terminals in one. II provides the user
with the choice of either full APL. full
upperllower case ASCII, or upper case
TIY in one reliable, easy-la-use hardcopy terminal.

The LA 180 OECprinler I is an inexpensive 7x7 dot matnx 132 column pnnter
that prints at 180 characters per second.
It features the 128 character ASCII upperlower case print sel an exlenSlVe array
of human engineering features, and
may be used either locally or as a remote prmter hard copy unit.
The OECpnnter I extends the fieldproven technology of the LA36 DECw(lier II into applications demanding
higher speed capabilities.

Hardcopy Terminal.
CHARACTERISTICS

LA35 RECEIVE
ONLY

LA36

LA37APL

LAl80 RECEIVE
ONLY

Pnnlspeed
(charsJsec.)

10/15/30

10115130

10/15/30

up 10 180

Pnnt positions
per ~ne

132

132
(with 133 bit buffer)

Characler sel

96 ASCII upperl
lower case

Full APL; Full ASCII
upper case TIY

128 ASCII upperl
lower case

Character
formaoon

7'11.7 dot maim:

7'11.7 dot matrix

7x7 do t matrix

7x7 dot matrix

Inlerfaces

20mA standard;
EIAophonal

20mA standard;
EIA optional

20mA standard ;
EIA optional

Parallel

·01 COPieS

Original +6

Original +5

Purpose of Unit

A hardcopy output
device (e.g . CRT
display attachment)

Interactive
hard copy
terminal

APL Terminal

A medium-speed
hard copy unit

Comments

Basically an LA36
Without keyboard

Prices include
controllerI interface
to attach to PDP-B
or PDP-l1

DECscopes-DIGITAL's VT50 series
of character oriented video terminalseliminate the need for electromechanical devices. They are all simple foroperators to master, quieter than mechanical terminals, and inexpensive. The
three models-VTSO, VTSOH, and VT52
-differ only in advanced application
features.
The VT61 is the first DECscope that
can transmit in either block or character mode. It offers over 80 commands, including character and line
insertion and deletion, text justification,
reverse video and protected forms, and
a number of other editing features not
found on the VT50 and VT52 DECscopes.
The VT61 is an upper and lower case
ASCII video terminal with a 1920 character display and 19-key function pad.
However, the VT61 uses a faster microprocessor with larger memory than do
the other DECscope models, so it can
offer more stand-alone capabilities.
30

CRT DiapYy Terminal.

Yr52

Vf61

12x80
(960 chars.)

8Ox24
(1920 chars.)

24x80
(1920 chars.)

5,7

7,7

7,8

64 ASCII upper case

96 ASCII upper/
lower case

128 char, upper/lower

Character set
Keyboard

Standard typewriter

Standard typewriter
plus 19-key pad
(10 numeric, enter,
period & 3
unlabeled function
keys)

Standard typewriter
plus 19-key pad
(10 numeric, enter,
4 censor, period &
3 unlabeled function
keys)

DEC standard + 19key pad + 12 user
defined keys

CommunICatIOns
Itlterface

20 rnA std. EIA
optIOnal

20 rnA std., EIA
optional

20 rnA or EIA
standard

20 rnA std., EIA
optional

75·9600

75-9600

Data rales (bps)
Editing capabilities
-Etaseto end of hne
-Erase to end 01

yes
yes

yes
yes
yes

CHARACTERlSTICS

VfSO

YrSOH

Screen formal (lines
and charsJhne)

12x80
(960 chars.)

Character matnx

saeen
-Downward scroll
-Upward scroll
-Insert/delete
character
-Insert/delete hne

yes

Cursor control

Cursor movement
via ESCAPE
sequences

Direct cursor
addressing

Direct cursor
addressing plus
cursor keys

OpllOnal features

No optional
attachments

Electrostatic
copier, LA35RO

yes
Direct cursor
addressing
LA35
LAI80
202T modem
interface

Asynchronous

Communications
Asynchronous communications equipment, with associated terminals, serve
a broad spectrum of user needs within
the DECsystem-l0 interactive environment. These needs include interactive

program development, operator control of the system, program production
and control, data entry, program and
data preparation, interactive problem
solving, student instruction. and information storage and retrieval. to name a
few. Asynchronous communications
is used to link the DECsystem-1O with
terminal equipment of three types: hard
copy, such as the LA37 or LA36 DECwriters, CRT terminals such as the VT52
DECscope. and buffered terminals.
such as the new VTSI.

Local terminals within 1500 feet of
the computer site can be connected
over dedicated hard-wired lines. Remote terminals located beyond this
distance are connected over dedicated
or dial-up telephone lines.
Speeds of asynchronous hard-copy
terminal equipment generally range
from 10 to 30 characters per second.
CRT terminals range in speed from 10
to 960 characters per second, depending upon their communications interface and type of line used for
transmission.

The goal of an interactive terminal
system is to match all users to the system in such a way that they feel the
terminal is identified closely With the
computer. In this way, the machine becomes an easy and natural extension
of each applicaUon. To do this, the computer must be a willing partner In the
interchang e so that the user feels that
he is in con trol of the terminal. and not
the reverse. TypicallY,a usertypesinput
sporadically, occasionally makes mistakes, and re ads fast on output. The
Data Communications system for the
DECsystem-l0 has been engineered to
deal with these user characteri stics.
The system, which includes hardware
and software elements, accepts characters at uneven rates, allows for single
character or line correction of mIStakes,
and allows the user to type at his own
speed-even typing ahead of the computer's response to his characters
When users are entenng large volumes
of data and need no prompting. the system accumulates data and antiCipates
ongOing entries so that the user can
con tinue to type despite fluctuations In
the system's re sponse.
Features of DECsystem-tO asynchronous communications include the ablhty
to delete one or more characters, delete
entire lines, retype lines and characters,
interact on a character or complete hne
basis (depending upon the application),
suppress unwanted output, and make
use of prompting messages to call for
input. Terminals may communicate With
the system administrator or operator at
the central or remote sites as w ell as
with other terminals.
34

Synchronous
Communications
DECsystem-1O synchronous com·
municatlOns provides error·free, hlQh·
speed paths between the central com·
puter and remote stations or other
computer systems. DECsystem-l0 synchronous equipment controls trallSmission over high-speed synchrOOOlJs
hnes. ThiS transmission isonamessage
basIs In contrast With the character-bycharacter baSIS of lower-speed. asynchronous transmissIOn.
Full duplex protocol software SUp'
plied With the OECsystem-l0 makes
efficient use of hlQh-speed tJansml$SlOll
In both directions simultaneously on a
full-duplex hne. Front end hardwareand
software handles hardware control.
message formatting, and message acknowledgements. The data transm~
IS "plpellned", a technique whICh Ill'
creases line efficiency by fully overlapPing the acknowledge-conbnue Sl9na1s.
TransmiSSion errors are detect~
uSing block-Qnented techniqueS In·
cluding longitudinal data checks. Data
errors are corrected through retrall Sk Hard-d
mission of the erroneous bloc·
ware is available to interface to a brOS
range of communications moderns.

Synchronous vs.
Asynchronous
Transmission
Asynchronoos transmiSSIOn IS employed 10 transmit data on a characterby-eharacter baSIS; synchronous trans-

mISSIOn IS preferred for mOYlng large

tb:ks of data. Asynchronous transmisSIOn, at 2400baud, Is limited to conveyngnomorelhan240etghl-brtcharacters
per second, synchronous transmISSIOn
al 2400 bltsJsecond. can convey
etght~ characters per second This
drtIerence comes about because synchronous transmISsion uses Independ-

30Ci

en~ bIock'oflented clock synchronization , wh'lI e asynchronous transmission
re-establlshes its character-orlented
dock synchrOnization With each char:~Ier Thus, In the asynchronous case,
ch eight-bit character requires minimally• one start bit and one stop
• bit.

The most important distinction between asynchronous and synchronous
methods of transmitting data is the
means of error detection and recovery.
Error detection for asynchronous devices is normally accomplished by insertion of a parity bit into the data field
of each character transmitted. Halfduplex (local character echo) receivers
will typically check this parity bit and
nobfy the sender of the eXistence of an
error. In full-duplex systems, such as
the oECsystem-l0, the character echo
is generally provided by the communications computer (oNB7, oAS80, etc.)
to which the user is immediately
attached. In thiS case, transmission error
detection and corrective action are
thus the responsibility of the sender,
whO simply compares what was sent
With what the computer says it received.
The communications computer which
echoes the character to the user then
guarantees that it will deliver that character, without error, thrOugh the network, to the appropriate oECsystem-l0
host.
35

This mode of error detection is highly
efficient and fully acceptable for interactive, terminal-oriented systems, but
is less efficient and less than acceptable
for message-oriented com m unications
with other computers. Synchronous
communication normally uses a blockoriented error detection technique,
such as the Cyclic Redundancy Check
(CRC-tS) polynomial. This technique is
most efficient for block-oriented data
transmission and for this reason, communications with remote computers is
accomplished using synchronous data
transmission.

Remote
Communications
Prior to the current fine of OECsystem10 remote communications products,
each remote user had been individually
linked to the computer center by separate long-distance telephone lines.
The only device that the remote user
had available at his location was the
terminal; he was able to utilize available
devices at the central station, but he
could not obtain output other than his
terminal output at the remote site. Either
the user had to travel to the central station to obtain a listing, or he had to have
the listings delivered to him. However,
with remote communications hardware
and software, listing files and data can
be sent via a single synchronous full duplex line to a small remote computer.
That remote computer in turn services
many remote peripherals, including terminals, card readers and line printers.
This eliminates the need for the user to
travel to the central site to obtain his
output. The remote computer and its
associated peripherals constitute a remote station.

Remote station use of the central
computer is essentially the same as
local use. All sharable programs and
peripherals available to local users at
the central computer station are also
available to remote users. The remote
user specifies the resources he wants
to use and, if available, these resources
are then allocated in the same manner
as to a local user. In addItion to utilizing
the peripherals at the central station,
the remote user can access devices
located at his station or at another remote station. Local users at the central
station can also make use of the penph erals at remote stations. Therefore, by
specifying a station number in appropriate commands to the operatIng system, each user of the DECsystem-l0 IS
given considerable flexibility in allocatlng
system facilities and In directmg Input
and output to the station or DECsystem-l0 of his choice.

The DECsystem-1O allows for sImultaneous operation 01 multiple remole
stations. Software provisIOns are 11lCOfporated in the operating system to d~
ferentlate one remote station from
another. By utilizing peripheral devICeS
al various statIOns, the user IS provided
With Increased capabilities. For example,
data can be collected from vanous remote stations, compiled and processed
at the central station. and then the realts
of the processing can be sent to aI
contributors of the data.

Complex Topologies
This is the name given to a group of
general network building capabilities
which, when put together. allow the
user to make many different cost, performance and high availability tradeoffs so that his network may be configured In a way which IS very much optimized
for him and therefore very favorable to
his environment. These building block
capabilities are :
Route-thru
This is the ability lor 8 Remote Station
to send information to a DECsystem-l0,
via the Universal Front End, to which it is
only indirectly attached - i.e., indirectly
through another Remote Station Of Universal Front End. This is most easily
Illustrated In the following picture:

~ Topologies
The most basic network topology is
It IS

~1-I01>Otnt. or star topology

--... .

iustrated by the folowlng diagram

•

, E_

. .n

1 -

.. ,- -.."

Information flows from A to C only by
being routed through B. This is a very
useful price performance trade-off since
the cost of a communications line from
A to B and from B to C may be substantially cheaper than Ihe cost of lines fr om
Ala C and from B to C.
37

Multi-pathlng
This is the ability to have more than
one path between nodes in the network. In general, these links are automatically load leveled depending upon
the relative speed and error rate of the
lines. This is best illustrated by the fol·
lowing diagram:

IXCsystem-1O

ON"

,
- 0"'" F

r ~al

DN87S

""'"

'''''' r"c,
The two links between A and B will
be automatically load leveled with data
flowing through each link. This may be
a desirable configuration for high availability systems with, for example, one
link via microwave and one by ground
link. This would allow degraded operation if either link went out for any reason.
There are also two routes from 0 to A.
The direct link could be a high speed
link, while the link routed through C
could be lower speed and used as hot
backup to the direct link. Again, both of
these configu rations have desirable
benefits that the user, in building his
network, can pick and choose from
depending upon his specific needs and
desires. The ability exists to pick and
choose rather than having a very rigid
set of network configuration rules.

Multiple Host Support
If there is morethan one DECsystem10 in a network, the Universal Front
Ends on the DECsystem-10s may be
hooked up to each other via a synchronous link, or the Remote Stations may
be hooked up to each Universal Front
End. This allows Teletype users anywhere in the network to select on an
individual basis, before they LOGIN,
which DECsystem-10 they wish to
LOGIN to. This is accomplished by
means of the SET HOST command.
Dynamic Topology
This feature allows individual nodes
in a network to go down or come up
without affecting the remainder of the
network. The exact implications of an
individual node going down depend on
the type of node and its network functions, but any new node may be added
to the network dynamically.

Task·to·Task
Communication
DECneHO provides the capability to
have tasks or jobs in dIfferent and geographically removed processors communicate with each other in a straightforward manner. These Jobs appear to
each other as mere 110 devices much
like a magtape. Jobs in different DECsystem-lOs may communicate WIth
each other, or DECsyslem -l0Jobs may
communicate with other DECnet systems, such as RT-11, ASTS, RSX-l1 M, D,
& S, lAS, and ATS-8 when they are
equipped with DECnet software.
This interprocessor commUnication
allows only for jobs to talk to each other,
not for terminal concentration. It does
not directly allow for remote file access,
remote device access or program sharing. It does, though, present a mechanism or a building block which could be
used to provide those features.
38

IBM
Device Emulation
and Termination
Through the use otl8M deviCe emit"
latlon the DECsystem-l0 can be a.l·
tached to an IBM 36OI370compulerV18
a synchronous link.. The DECsystem-10
will be treated by the IBM system as drt
were an IBM 2780 or 3780 or HAS~
multHeavlng remole statIOn. This tacitates job submiSSIOns and liIetransfers
back and forth between the twO com'
puter systems.
Through IBM devICe lermin91JOtllBM
2780's, and HASP multHeavmg Vo'O~
statk>ns can be used as Remote J
· bS 11110
Entry statJons to enter bale h jO
the DECsystem-l0: batch .lObS may:
placed in the card reader 01 the 27
3780 or HASP work statIOn. read .,to
d ndhaVe
the DECsystem-l0, eICecute a 3700
their output returned to the 2780.
or HASP work stallon hne ponler

DM87/DM87S
Universal

Synchronous!
Asynchronous
Front End Subsystem
The DECsystem-l0 data communi-

caoons products are based on the
DN87 Unl\'ersaI Synchronous/Asynclvonous Communications Front End
Subsystem The ON87 IS conftgurable
nasynchronous only mode (up to 112
asynchronous Imes). synchronous
only mode (up to 12 synchronous hnes)
or ""lth a mIxture of synchronous and
asynchronous bnes In the same DN87
These three modes allow the DN87 10
be configured very cosl effectIvely In a
wide vanely 01 customer specific conliguratlons This greal lIexlbdlty is the
essence 01 the DN87 Communications
Subsystem
The DN87 is capable 01 synchronous
oommunicabon WIth the DAS80 series
Remote Stallons. the DAS92 Remote
StatiOn and the DC72NP Remote Station. ThesealowRemoleJobEntry, Remote ConcentratIOn 01 Interactive Teletype lines or a comblOa!)on of the two
The DNa7 WIth these Remote StallOns
supports complex topologIes such as
multt-pathang, route-Ihru, and multIple
host support WIth DECnet-IO. It IS pos$tie 10 t\ave a DECsystem-IO commu'
IllCate 'NItti any DECne! system-for
example RSX-l1M, RSX -l1D, RSX-1IS.
~, RT-Il , RSTSIE. RTS-8, OECsystemor OECSVSTEM -20 If equipped
""Ilb DECnet software
The ON87S has the same funcllon ably as aDN87 excepl that It is attached
10 the DECsystem -IO vIa the OTE1D
IOletface rather than Ihe OLtO Up to
~~ee ON87S's may be attached to the
EIO Interface The DN87 and the
DN87S reqUIre TOPS-IO versIOn 603
or later mORllor release

Asynchronous FuncUonatity
On an eight-line group basis, the
ON87187S is capable of terminating
20 mA current loop, local EtA or EtA with
full modem control type of asynchronous linelterminal interfaces. On an
indIVidual line basis the oN87/87S
asynchronous lines can be :
• ASCII Teletype-compatible code or
2741 EBCD or Correspondence
Code.
• Full duplex WIth echoplex (i.e. echo
generated by computer) or lullduplex With local copy (simu lated
hatf-duplex).
• Program selectable hne speeds of
from 50 through 9600 baud.
• Split transmiureceive speed s.
• Automatically baud rate detected
for 110, 134.5, 150and 300 baud lines.
Some off-loading of the DECsystem10 host is accomplished. in that the
DN87/87S does the majority of the
echoing for asynchronous lines. It does
nol echo special characters, nor does it
echo when the user Is in character-ata-time mode (e.g .• OoT - when an individual character can be a command).
The DN87187S also does fill character
generation.
39

Synchronous Functionality
The DN87/87S is capable of terminating EtA and/or current-loop type synchronous links. The line speeds may be
2400, 4800,7200, 9600, 19.2K, 38.4K or
40.8K baud on an individual line basis.
These links operate only in full-duplex
with simultaneous bidirectional trans'
mission. The synchronous links use
ODCMP protocol for error checking
and correction and for poinHo-point
link control.
These synchronous links communi·
cate only with the DC72NPRemoteStation (DC72NP is a software only upgrade of the DC71 or DC72) , the DAS80
Series Remote Stations, the OAS92
Remote Station or another DN87/87S.
On an individual synchronous line basis
the DN87/87S can also comm un icate
on a task to task basis with systems running DEC net software.

Options List
The DN8? is the Universal Synchronous/Asynchronous Front End CommUnications Subsystem. Software to
provide complex topology support is
included with the DNa? The DN8? requires the addition of DNB1-xx synchronous and/or asynchronous line options.
ON87-DA, DB -DNB7 including D110-C
port only. Requires D110-A with available port. Note that this is what would
be ordered with a 1080 or 1060 System
Package, which includes a DUO.
DN87-AA , AB -DNB7 including Dll0-A
Communications Interface and one
DL 10-C port.
DN87S-AA, AB -DNB7 with
interface.

OTEIO

ASYNCHRONOUS LINE OPTIONS
DNB1 -EA, EB -Asynchronous Expansion Cabinet including one ONB1 -EC
16-Line
Asynchronous
Expansion
Group. Requires two ONB1 -Fx 8-Llne
Terminator Groups to activate the Imes
ON8l -EC, ED -Asynchronous 16-Lme
Expansion Group This reqUires two
DNB1-Fx 8-Une Termmators to activate
the lines.
ON8l -FA -B-Llne Terminators each
with 20 mA Current Loop Local Interfaces.
ON8l -FB -B-Llne Terminators
with EIA Local Interlaces

each

ON81-FC -B-Llne Terminators each
with EIA Full Modem Control Interfaces
ON81 -FD -B-Llne Terminators with Integral Auto Answer Modems (These
modems reqUire customer supplied
DAA'S).

SYNCHRONOUS UNE OPTIONS
ON81-EE, EF-SynchronouS ExpansiOn
Cabinet Includes one ON81+1
ON81-H -Synchronoos line controller
Expansion Line For data transm: _
speeds of up to IOKbaudandfora
men! to EIA RS232C compatible m0dems
oIIef
ON 81-J -Synchronous line ~:rup 10
For data transmISSIOn speeds It 303.
408K baud and for attach men 0
type current mode modems
.
ns are such
NOTE · Option destgnatlO
the
lOnS
•
deslgnal
that if there are two
nd is
first is 115V/60Hz and the seeo tjO(I
230V/SOHz. lf there i~ onJ.y a ~;~wer
designation that option IS N
dependenl

H.rdw.re Configuration Guidelines
ApIctonal representation of the DN87
cabinet arrangements should help to
Simplify the explanation 01 the configurabon rules

DUQ-A

A synchronous Conflguratton Rules
• The DN87cabinet(DN87-AorDN87D) has no available mounting space
for asynchronous lines.
• If any asynchronous lines are required a DN81-EA Asynchronous Expansion Cabinet must be ordered.
This cabinet includes one DN81-EC
Asynchronous lS-Une Expansion
Group and has available mounting
space for up to three additional
DN81-EC units. Therefore, the DN81EA is capable of containing up to 64
asynchronous lines.
• A maximum of two DN81-EA Asynchronous Expansion Cabi nets are
permitted per DN87.
• Each DN81-EC Asynchronous t6Line unit requires two DN81 -Fx (FA,
FB, FC or FD) 8-Line Terminators to
activate the lines.
DN87-D or DN87S
INCLUDES
PDP-11I40
16K MEMORY
(DN87),32K
MEMORY
(DN87S) AND
INTERFACE

PORT
AVAJLABLE
MOUNTING
SPACE FOR UP
TO 4 DN8t-H/J
SYNC LINE
UNITS

DN81 -EA

DN81-EE

INCLUDES
ONE DN81-EC
16-L1NE ASYNC.
EXPAN . UNIT

INCLUDES ONE
DN81-H SYNC.
LINE UNIT

AVAILABLE
MOUNTING
SPACE FOR
UPT03
ADD ITIONAL
DN81 -EC

AVAILABLE
MOUNTING
SPACE FOR
UPTO 7
ADDITIONAL
DN81-H

"
- - - - -V-- - - - - - )
DN87-A
LINE MAXIMUMS PER DN87/ DN87S
Max. No of
Svnc . Lines

Max. No. of
Asvnc. Lines

112

64
32

• Proper number of async hrOnous
lines are made up using the Asynchronous Configuration Rules from
above.
• Proper number of synchrOnous
lines are made up using the Synch ronouS Configuration Rules from
above.
41

Synchronous Configurations Rules
• The DN87 cabinet (DN87-A or
DN87-D) has available mounting
space for up to four DN8t-H/J synchronous line units.
• If more than four Synchronous Line
Units are required a DN81-EE Synchronous Expansion Cabinet must
be ordered. This cabinet includes
one DN81-H Synchronous Line Unit.
and available mounting space for up
to seven additional DN81-H units.

Complex Topologies
Complex topologies are available to
all DECsystem-10s using the DASao
Series Remote Stations and the ONS7
Front End (includes OC75NP and
OASaS) with the 6.03 version of TOPS10. This means that route-through, multpathing, multiple host Support and dynamic topologies (SET HOST monitor
cOmmand) are all a standard part of the
6.03 monitor a nd availa bla to those who
have the appropriate communications
hardware and software configurations.

Oll"l,tal Network Architecture, .imPIe',,"
lopermented across a wide range 0 . ec
allng systems and hardware areM ;
tures, enables users to build a vanetyO

DECna-1O
DEene! is the set of software products
which extend various DIGITAL operat-

ing systems so they may be intercon nected with each other to form computer networks. The DEene! user can
configure a variety of networks, satisfy'
ing a variety of constraints, by choosing
the appropriate CPU's, line interfaces
(and speeds) and operating systems
software,

networks,
essor
OECnet-tO provides interproc th
task-to-task communications IO~om~
OECsystem-l0. Thus users may
.
baSIS
munlcate on a program I0 pr ogram
thrOugh
with any other DEenet system
d
'
'II
inclu
the ON87 Iront end. This WI
RT-tte
RSX-ltS, RSX-tlM, RSX-l1D, lAS,
RSTS, RTS-8, DECSYSTEM-20
other OECsystem-10s.

and

DAS80Series
Remote Station
The oASSO Senes Remote Stations
are a famity of remole stations with a
wide range 01 functionahty The DAS80
is a Remote Job Entry Sl ation with a
lX)cprn card Reader, a 300 Ipm Lme
Pm!efandanLA36Console TheDAS81
is a Remote Concentrator capable of

concentrating up to 32 asynchronous
lines.The OAS82Is acombine lion 01the
DAS80and DAS81.lacllltatlng both AJE
Md Remote Concentration
WIlen ~nked to a ON87/0N87S Uni-

versal Front End the DASSO Series Remote StatIOns wIn support complex
topolOgieS such as route-thru. multipatluog,aod multiple host support

Asynchronous Functionality
The asynch ronous terminal lines altached to the DASSO Series Remotes
have the same functionality as the
asynchronous lines attached directly
to the DN871DN87S.
Synchronous Functionality
The synchronous line is used as a full
duplex dedicated line to anyone of a
DC75NP, DAS850r DN87/ DN87S DECsystem -lO Front Ends. The OAS80 Series Remote Stations are all downline
loada ble from the OECsystem-l0
through the synchronous link.
Unit Record Devices
The Line Printer (LP) and the Card
Reader (CR) on a OAS80or DAS82 Remote Station are available from the
OECsystem-l 0 host In a transparent
manner. This means that any user at
any terminal can use this remote LP or
CR very Similarly to how he would usea
LP or CR attached directly to the host.

This is accomplished by use ofthe DECsystem-lO Mo nilor Command LOCATE
which sets the default LP and CA for a
specific user.
The LA36 DECwriter, which is included
with the OASBO Series Remotes, can be
used as the Operator Controlling Console for the spoolers which are running
for the LP and CR at that station. This
means that any operator-type requests
(e.g., LP out of paper) appear at the remote location with the LP and CA rather
than at the host.
Host Interfaces
The DASBO Series Remote Stations
can only communicate with the OECsystem-tO via Ihe DC75NP, the OASB5
or the ONB7/0NB7S Front Ends. The
DN87IDNB7S requires the 6.03 or later
version of the TOPS-tO monitor, while
Ihe OC75NP and the OASB5 require the
6.02A or later monitor. The DC75 Front
End will not run under 6.02 or later monitors unless it is equipped with the " NP~
upgrade (additional 4K memory, KG11
CRC unit and software).

OPTIONS LIST
DASeO-AA, AB - Remote Batch Station
Includes t DN81-H, lA36 Console,
DAS80-CA/CB, DASOO-lA/lB, PDP-lt
and software,
DAS81 -AA, AB - Remote Concentrator
Includes PDP-tt , 1 DN81-H, DN81-EA
and software. One more DN8l-EC can
be added fora total of 32 asynchronous
lines.
DAS82-AA, AB-Remote Batch Station
and Concentrator. Includes PDP-11,
LA36 Console, DAS80-CNCB, DASeoLNLB, DN81-H, DN81-EA and SOftware.
DN81-Fx asynchronous irterfaces are
also required and must be ordered
separately.
UNIT RECORD OPTtONS
DAS8O-CA, CB-CardReader,300cards
per minute.
DASeO-LA, lB - Printer, 300 lines per
minute, 132 printing positions, 64 printing characters, EDP character set.
DAS80-LC, lD - Printer, 230 lines per
minute, 132 printing positions, 96 printing characters, EDPcharacter set.

ASYNCHRONOUS LINE OPTIONS
DN81-EA, EB-Asynchronous Expansion
Cabinet including one DN81-EC 16 Une
Asynchronous Expansion Group. Requires two DN81-Fx 8-Une Terminator
Groups to activate the lines.
DN81-EC, ED-Asynchronous 16-Une
Expansion Group. This requires two
DN81-Fx 8-Une Terminators to acllvate
the lines.
DN81-FA -8-Line Terminator each with
20mA Current Loop Local Interlaces.
DN81-FB -8-line Terminators each with
EIA Local Interfaces.
DN81 -FC-8-Une Terminators each with
ElA Full Modem Control Interlaces.
DN81-FO-8-line Terminators with Integral Auto Answer Modems. (These
modems require customer supplied

DM's).
44

SYNCHRONOUS LINE OPTtONS
DN81 -H -Synchronous Line Controller
Expansion Une. For data transmIssion
speeds of up to 10K baud and for attach·
ment to EIA RS232C compatible
modems.
DN81 -J -Synchronous Une Controller
For data transmission speeds of up to
40.8K baud and for aUachment to 303type current mode modems.
Note: These same line options (DN81-)[X)
are used on the DASBO series remote
stations, as described here. on the
DN87 and for DC76 add-ons.

DASH
RemOte Station
The DAS92 Remote Station is a low
costremote,lObentryconcentra!Orl hat
is attached to the DECsystem -l 0 via
one synchronous link to a ON87/DN87S
fion! end The OAS92 may be canfigured in one of the following manners
1 up to 16asynchronous terminal hnes
2 up to 12 asynchronous lermlnal llnl3s
plus a card reader Of line printer
3. up to 8 asynchronous terminal lines
plus a card reader and Ime printer
Only one synchronous interface Is
permitted on Ihe DAS92 therefore the
DAS92 must be a sequenlial node This
means 11 may nol do multi-paining o r
route-thru Data to the DAS92 may be
routed from some other node, but no
data maybe routed through the DAS92
Sll'lCe It IS onty capable of haVing one
synchrOOOYs Itnk

Options
1. DAS92-AA, AB Basic Unit, including
16K, PDP-8/ A processor, VT52 console
terminal, desk, RO M for down-line loading, one (1) synchronous line interface
and software. Requires at least one (1),
buta maximum of five( 5 ) optional units
listed below :
(a) DAS92--EA Asynchronous 4...Jine
multiplexer, including line drivers.
The DAS92-EA Asynchronous 4-line
Multiplexer will accommodate either
20 rna . or EIA lines in any mixture.
One out of every four can be full
modem control. The baud rate is
switch selectable anywhere from 50
to 4800 baud . Maximum of four (4)
OAS92-EA's per OAS92-A.
(b) DAS92-CA, CB Card Reader.
The DAS92-GA, CB Card Reader is
a Digital CR8-F for 8O-column (only)
cards, and operates at 285 CPM .
Maximum of one (1) Card Reader per
DAS92-A.
(c) DAS92-PA LAl80 Printer. The
LAl80 operates at 180 characters
per second and uses a 96-character
set (upper and lower case) . The
carriage is 132 columns wide. Maximum of one (1) LAl80 per OAS92-A.

(d) DAS92-VA, VD LP05 Line
Printer, (64-characters). This is the
LP05 (LE8-V) and operates at 300
lines per minute using a 64-character set. The carriage is 132 columns
wide. Maximum of one (1) LP05 per
DAS92-A.
(e) DAS92-WA, WD LP05 Line
Printer, (96 characters). This is the
same as the DAS92-VA except that
it uses the 96-character set (upper
and lower case). Maximum of one (1)
lP05 per DAS92-A.

i
I

DAS6l -EA, EB -Synchronous Expan sion Cabinet for expansion past 4 synchronous lines. Includes no synchronous lines.

DAS61
IBM i780/3780
FRONT END
The DAS61 Front End allows IBM
27BOand 3780emulation and termination. This means that IBM 2780's and/or
3780's can be used as RJE stations into
the DECsystem-l0 or that the OECsystem-10 can emulate (or simulate) an
IBM 2780 or 3780 to an rSM 360/370
computer. The DAS61 can handle a
maximum of 12 synchronous lines each
operating independently with any combination of 2780 or 3780 emulation or
termination. The maximum aggregate
throughput of a DAS61 is 100,000 bits
per second (tOOK baud). The DAS61-0
is interfaced to the DECsyslem-l0 via
the DUO and the DAS61-S is interfaced
via the OTEtO. Multiple DAS61's are
supported per DECsystem-l0.
OPTIONS
OAS61-0A, DB -IBM 2780and/or3780
Emulation and Termination Front End.
Including Ol1D-C port and requiring
OL 10-A with available port. Requires
addition of OAS6t-H and/or OAS61-J
synchronous line units.
DAS61 -SA, SB - IBM 2780 and/or 3780
Emulation and Termination Front End
including OTE10 interface. Requires
addition of OAS61-H and/or DAS6l-J
synchronous line units.

DAS6l-H -Synchronous Single Une
Controller for data transm Iss ion speeds
of up to 10K baud and for attachment to
EIA RS232C compatible modems.
DAS6hJ -Synchronous Single Une
Controller for data transmission speeds
of up to 50K baud and for attachment
to 303-type current modems.
DAS6l - QC-DAS61 SoHware Only.
DAS6l -Q X - DAS78 to DAS61 SoHware
Only Upgrade (prerequ isite GALAXY).

DAS6i
IBM HASP
MULTI-LEAVING
FRONT END
The DAS62 Front End combines all
of the functionality of the DAS61 with
support of IBM HASP multi-leaving
work stations as DECsystem -l0 RJE
stations and also allows for the DECsystem-l0 to simulate a HASP multlleaving work station to an IBM host
computer. The DAS62 can handle a
maximum of 12 synchronous lines each
operating independently with any combination of 2780 or 3780 or HASP multileaving emulation or termination. The
maximum aggregate throughput of the
DAS62 is 100,000 bits per second (tOOK
baud). The DAS62-D is interfaced to the
DECsystem-l0 via the DL10 and the
DAS62-S is interfaced via the DTE1O.
Multiple DAS62's are supported per
DECsystem-l0.
46

OPTtONS
DAS62-DA, DB - IBM 2780 and/at 3780
and/or HASP multi-leaving worX stallon
Front End. Including DUO-C port and
requires DL 10-A with available port Requires addition of DAS62-H and/or
OAS62-J synchronous line units.
DAS62-SA, SB -IBM 2780andfor3780
andfor HASP multi-leaving work station
Front End including DlElO interface.
Requires addition of DAS62-H andlor
OAS62-J synchronous line units.
DAS62-EA, EB -Synchronous Expansion Cabinet for expansion past 4 synchronous lines. Includes no synchronous lines.
DAS62-H -Synchronous Single Une
Controller fordata transmission speeds
of up to 10K baud and for attachment to
EtA RS232C compatible modems.
DAS62.J- Synchronous Single Une
Controller for data transmission speeds
of up to 50K baud and for attachmentto
303-type current modems.
DAS62-QC -DAS62 SoHware Only
DAS62-QX -DAS78 to DAS62 Software Only Upgrade (prerequisite
GALAXY)
DAS62-QY -CAS6l to OA56250ttware
Only Upgrade

•

:Q~:r

w~~

~~~
'00

':t:~~

'vv

""9
,•
>

ils "9
~§

••"

•
>

;;

•
ev

·,

.~ "

!~ •,9
g

•"0 ;;~•
~

~§ ,•e

~~ ,~

•

OK MTlM 1090 / 1099 Ct>lI~'1ON

CINnA!.
~U5Oo'

! I II

t~;,;;=}----------1""""""'~~~~'~"":J
"
(l,II,'A LINK

........11",[1.(.

>0 J

' " ro .,

01
1.1' 112
10 11
S'NOIIONOUS UNU
LINES
UP TO
.-.$YI'fCHlONOU5

UHO 3 UNE NJNTUS
2 CAlI) I'EAIlUS
I (oUt> P'UNCH

~"'TfU

(l,II,'A CH..,.,."l

CONUOl ~H20

"' •

UI' TO'

T"'f: OI:IVES

OA'A QV.NNlL

CONTROL

uP TO 10

~H20

'U'PiOi

MEMORY
MODULES

uP TO • DIS« OIIIVfS

DAtA

CHAtH:l

'" ro J

C~fl

... ro,

CENTRAL

PtIOCESSOII

(UP TO 32 PER SYSTEM)

CONTfIOlLER

'" ro J
COMI''',"CAIIONI UP TO 112 ASYNCHIIONOUS LINES

MlA'IP'LEXU
UP TO'

I 011 uP TO 12 $'If\JCHItONOUS LINES

UP TO 8 DfCTAPES

MAX. NO

sup·

OPTION DESIGNATOR
115V/60Hz 230V/SOHz
Central Processors

DESCRIPTION

PREREQUISITE

PORTED
(NO TE I)

KA 10-A, KA 1O-C

KAlO Central Processor; 366 hardware InstructIOns,
10-character-per-second console lermlnal

None

KltO, KltO

KIlO Central Processor. 378 hardware Instructions.
memory paging, instruction look-ahead, virtual
memory, IO-character-per-second console terminal
KL to Central Processor; 395 microprogrammed
instructions, bUSiness instruction set, high-speed
cache memory, virtual memory. Instruction lookahead, 3O-character-per-second console terminal

None

MFtO-A. MFtO-A

MFlO Core Memory; 32K words olt o-mlCrOSecond
memory.

KAlO, KIlO or KLlO

Nole2

MFtO-E, MFlO-E

MFlO Core Memory eKpansion module: 32K words
of t.O-microsecond memory 10 eKpand MFlO-A

MFlO-A

NOle 2

MF10-G, MFIO-G

MFtO Core Memory: 64K words olIO-microsecond
memory.

KAlO, KilO, or KL10

Note 2

MGtO-HA

MGIO Core Memory; t28K words 011.0
microsecond memory

KA-lO, KltO. or KLlO

Nole 2

MHIO-H

MH-lO Core Memory 256K WOrds oil 2
microsecond memory

KA-l0, KilO or KL10

Nole 2

MCtO-D. MClo-0
MCIO-F. MC10-F

Memory Access Port. lor MDlO Memones

MOlO

Memory Access Port: far MFtO Memories

MF10

MX10, MXtO

Memory Port MultlpteKer; prOVides direct memory
access for up to eight FDIO Data Channels using
lS-bil address logiC

MCtO

64
64
3

MX10-C. MX10-C

Memory Port MultlpleKer. prOVides dlreCI memory
access for up to eight DFlO-C Data Channels USIng
22-bJI address logic.

MelO

DFtO.DFlO

Data Channel; permits data Iransfer between hlghspeed devices and core memory; uses IS-bit
address logic

MClOor MXlO

DFtO-CA. DFtO-CB

Data Channel; permits data !ransfer between highspeed devices and core memory; uses 22-bit
address logic.

MCtO or MXtQ-C

DAS33

Bulfered Data Channe!; permits block data
transfers between 110 controllers and core
memory: contains 256-word dala buffer; uses
22-bit address logic

Avail. memory port
MXlO or MXtQ-C

Disk Drive: 5.12-million words capacity; average
access time 47.5 milliseconds. transfer rate
t5 microseconds per word

RPIO or RP1Q-C

Disk Drive; 1O.24-mllhon words capacity, average
access time 47.5 milliseconds. transfer rate t5
microseconds per word

APIQ-C

Disk Pack; additional disk pack for AP02 Of AP03
disk dnve.

RPD20r RPOJ

oJ,

Disk Controller; contrOller for up to eight AP02
and/or APOJ DISk Drives

DFtO or DF1Q-C

Disk Syslem: includes DF10 Data Channel, APlO-C
Controller and one AP02 Disk Drive

MCm, MX10

Disk System: includes DFIO Data Channel,
RPIO-C Controller and one AP03 DIsk Drive

MCIO. MXtO

KL 1O-8A. KL to-88

Memories and Channels

Disk Systems
RP02-A, RP02-B

RP03-AS, AP03-BS

AP02-P, RP02-P
APIO-CA. APtO-CB
AP02-CA, AP02-GB
AP03-CA, AP03-CB

OPTION DESIGNATOR
ltSVI60Hz 230VISOHz

MAX. NO.
SUPPORTED
(NOTE 1)

DESCRIPTION

PREREQUISITE

RPCW-AA. RP04-AB

Disk Drille , 20 48-mllllon words capacity; average
access lime 27 mltllseconds , transfer rate 56
m ICroseconds per word

RHPQ4-A, RHP04-8.
or RHPQ4-D

RPCW -BA. RP04·88

DISk D"ve. 20 48-mlUlon words capacity. average
access time 27 mllhseconds; transler rate 5.6
m ICroseconds per word, controller select option
lor attachment to two controllers

RHPQ4-E, RHPQ4-F,
or RHP04-H

Note 3

RPCW·C. RP04 -t

Controller Select Option ; converts RPQ4 ·A to
RP04 -B
Disk Pack , additional disk pack lor RPQ4 Disk Dnve

RPQ4-A

,I,

RP04-A or RP04-B

Disk System ; Includes controller and one RP04-A
DiSk Ofille
Disk System. Includes controller and one RP04-B
Disk Olive
Disk System , Includes DFlO Data Channel. conIroller and RPQ4 -A Disk Drive

oFtO or oFIO-C

DFtO or DFtO·C

MCIO.MXtO

RHP04 ·EA. RHP04 -EB

Disk System , Includes oFtO Data Channel, controller and one RP04 -B Disk Olive

MCt O, MXtO

RHP04-FA. RHP04 -FB

DISk System , Includes OFtO-C Data Channel.
controller and one RP04-A Disk Olive

MCtO, or MXtO-C

RHPOf-HA. RHP04+1B

Disk System . Includes DFtO-C Data Channel,
conlroller and one RP04-B Disk DrIVe

MCtO. MXIO-C

RTP04 -AA. RTP04 -AB

Disk System including Controller and RP04 -A
(lingle access) Olsk Dnlle
DISk System Including Controller and RP04 -B
(dual access) Disk Olive

KLtO-8

KLIO-B

RP04 -P. RP04 -P
RHP04·AA. RHP04 -AB
RHP04 -BA, RHP04 -8B
RHP04..[)A. RHP04 -DB

RTP04 -BA. RTPQ4 -BB
RTP04-C
RHP06-M, RHPO&AB
RHP06-BA. RHPOO-BB
RP06-AA. RPOB-AB

RPOS-BA. RPOO-BB

RP06-C
RTP06-M, RTP06-BB
RTP06·SA. RTPOG-BS
RTP06-<:
RHS04-{)A, RHS04 -DD

RHSCM -<:A. RHS04-CD

AHS04-GA, AHS04-GD
RHS04 -HA. RHS04 -HD
RHS04 -JA. RHS04 -JD

Dual Channel Access Kit
Disk System; Including Controller and RP06 -A
(single access) Disk Onve
Disk System. including Con troller and RP06-B
(dual access) Disk Dnve
Add.on Disk Olive (Single access) . Includes one
RP06-P Disk Pack 39, 40 million word capaci ty
average access time 27 milliseconds, tr ansfer
rate 5 6 microseconds per word
Add.1m Disk Dillie (dual access), mcludes one
RPOS-P Disk Pack 39. 40 million word capacity
allerage access time. 27 milliseconds. transfer
rate 56 microseconds per words
RPOS Dual Access Kit
Disk System Including Controller and RP06-A
(Single access) Disk D"ve
Disk System Including Controller and RP06-B
(dual access) Disk Dillie
Dual Channel Access Kit
Swapping DiSk , 256K words of swapping storage,
transfer rate of four microseconds per word; room
lor one additional RHS04-C
Swapping Disk . 256K words of swapping storage;
transfer rale lour microseconds per word . lor
elCpltnSlOn of RHSQ4-D
Swapping System , Includes controller and one
RHS04 -o Swapping DIsk
SwapPing System . Includes DFtO Data Channel,
conlroller. and one RHS04-D Swapping Disk
Swapping System . Includes DFtO-C Data ~hannel.
conltoller. and one RHS04-o Swapping Disk

KL 10-B. RTP04-A

NIA

DFIO or DFtO-C

DFtO or DFIO-C

RHP06-A or RHP06-B

RP06-A
KUO-S

KUO-S

KLtO-S. RTPOfi-A

RHSQ4-G. RHS04·H
or RHS04 -J
RHS04-D. RHS04-G
RHS04-H, RHS04-J

I"
I"

DF10 or DF10-C

MCIO, MXtO

MCtO or MXlO-C

OPTION DESIGNATOR
115V160Hz 230Vl5OHz
Magnetic Tape Systems

DESCRIPTION

PREREaUISITE

TUlOA-EE. TUtOA-EJ

Magnetic Tape Drive; 9-channel drive. 45-inchesper-second; recording densities of 200, 556 and
88 bpi.

TM10-A or n.lID-B

TU10A-FE. TU10A-FJ

Magnetic Tape Drive; 7-channel drive. 45-inches'
per-second; recording densities 01 200. 556 and
800 bpi.

n.41D-A or TM1D-B

TM10·AA, TM 10-AB

Magnetic TapeController; Interfaces tollO bus of
KAlO or Kl t O Central Processors lor control of
up to eight TUtOA M agnetic Tape Drives.
Magnetic Tape System; includes TMlO-A Controller
and one TUtOA Magnetic Tape Drive.
Magnetic Tape System; including RH10 and TM02
Controliers and TUI6-E 9-track, 45 ips Tape Drive

KAl00r KilO

TUl 0-CA, TUI O-CB
THU16-EA, THUI 6-ED

MAX. NO
SUPPORTED
(NOTE 1)

•
•

KA100r KilO
DFtO or DAS33

•

Recording densities 0180011600 bpi
TTU16-EA, TTUt6-ED

Magnetic Tape System including Massbus
Controlier, Tape Controller and TUI6-E
Tape Drive

KLlO·B

TUI6B-E, TUI6B-ED

Tape Controller and TU16-E Tape Drive
(for expansion beyond 4 dnves)

THU16-E or TTU16-E

•

TU I6-EE. TUt6-EJ

Add-on Magnetic Tape Drive, 9-track. 45 IpS
Recording densities of 80011600 bpi

THU16 -E

TU40-A, TU40-B

Magnetic Tape Drive; 9-channel drIve, 15D-lnchesper-second; recording densities 01200. 556 and
BOO bpi.

TU4Q-C. TU4t-C

TU4t-A, TU41-B

Magnetic Tape Drive; 7-channel drive, lSO-lnchesper+second; recording densItIes 200, 556, and
800 bpi.

TU4Q-C, TU41-C

TMIO-BA, TMtO-BB

Magnetic Tape Control; attaches to DFtO or
DFIQ-C Data Channel to control up to eight TU40
andlor TU41 Magnetic Tape Drives

DFtO or DFIQ-C

TU40-CA, TU40-CB

Magnetic Tape System; includes DFtO Data Channel, TM1D-B Controller and one TU40 Magnetic
Tape Drive.

MClO. MXtO

TU4 1-CA, TU4 t -CB

Magnetic Tape System; includes DFIO Data Channel TMlO-B Controller and one TU41 MagnetIC
Tape Drive.

MC10. MX10

TU70·AA, TU70-AB

Magnetic Tape Drive; 9-channel drive. 200-inchesper-second; recordIng denSItIes 800 and 1600 bpi

TU70-C

TU7t-AA, TU7t-AS

Magnetic Tape Drive; 7-channel drIve, 2OO-inchesper-second; recording densities 200. 556, and
BOO bpi.

TU70-C

TU7O-CA, TU70-CB

Magnetic Tape System; includes Data Channel,
controller and one TU7D-A MagnetIC Tape Drive
DECTAPE Unit; dUal-dnve OECTAPE.

MCtO, MXtO or
MXtQ-C

TU56-A, TU56-S

TOlO or TDtO-G

,.
2

•

TOtO-A. TOl0'B

DECTAPE Control; prOVides control for up to four
TU56 DECTAPE uOlts.

KAl0

TOtO-CA. TOto-cS

DECTAPE Control; provides control for up to lour
TU56 DECTAPE units.

KilO. KL10

TOl0-GA, TOtD-GB

DECTAPE System : Includes TD10 Controller and
one ru56 DECTAPE unit

KilO or KL10

Magnetic Tape System; includes DXtQ data
channel, TX02 tape control unit and TU72-E
9-lrack 125 ips Tape Onve. Aecordlng denSities
of 1600 and 6250 bpi.

KilO or KLtO

TU72-C

MAX. NO.
SUP~

DESCRIPTION

PREREQUISITE

PORTED
(NOTE 1)

Magnetic Tape D nve; g-track, 125-lnchesper-second. reco rdIng densllles 1600 and 6250
b..

TU 72-C

CRlo-DA. CRIO'OB

Card Reader, table-top card reader. l OOO-card sper mlnule

KAI O. Kil O or K11 0

CRlcrEA. CRIQ-EB

Card Reader , console card reader. 1200-cards-permInute

KA 10, KilO or KL 10

CRIQ--FA. CRIO-FB

Card Reader . table-top card reader. JOO-card s-permInute

KAI O. Kil O or K11 0

LSPIQ--LA. LSP10·LB

KAI O. KIlO or KL1 0

I. Note 5

lPIO-F

NfA

LPIO-F

NfA

LPIO-H

NfA

LPIO-H

NfA

KAIO. Kil O. KLI O

KAIO, Ki l O, Kl1D

KAIO, Kil O. K11 0

KAID. Kil O, KLI O

KAI O. Kil O, K11 0

LP01-YA

line Pnnter; 245-lines-per-m lnute. 54-character
print set
Pnnt Drum . 64-character EDP pnnt drum fo r
lPIO·F line Prin ter
Print Drum . 54 -character SCientific Print drum
lor LPI O-F line Pnnter
Pnnt Drum. 96-character EDP Pnnt drum for
LPIO-H Line Pnn ter
Print Drum, 96-character SClenllhc Prml drum for
LP1Q-H Line Printer
LIne Prlnter , I,250-lInes-per-mlnute. 54-character
EDP prin t set
LIne Pnnter, 1.250-lInes-per-mmu te. 64-character
SclOntllic prlnl set.
Lme Pnnter. 92S-hnes-per-mlnule, 96-character
EOPpnnt sel
LIne Pnnter. 925-bnes-per'mlnute, 96-characl er
Sclenhhc pnnt sel
LIne Pnnter , up to 15OOLPM , EDP pnnt set see LP07· Y
Charaband lor LP100 with 2 sets of 64-char lonts

LP100-B

LPOH8

Charaband for LP100 with 2 sels 01 96-cnar fo nls

LPIOO-B

LP07-YC

Charaband tor LP100 wIth 1 set of 64-char. lonls
and 1 sel 01 96-char fon ts
PloUer ContrOl , l or CALCQMP M odel. SA3 or 565
plott er or equIvalent
Plotter , CALCOM P Model 565 plotter with con tr ol:
uses 12-lnch paper ; speci fy step sIze
Sleps/m inute
Step sIze
18.000
001 Inches
18,000
005 Inches
18.000
I Inches

LPIOO-B

NfA
NfA
NfA

KAI O. Kil O. KLIO

KA 10. KilO. K110

KAI O, KilO. K110

OPTION DESIGNATOR
nSV/6OHz 230V/ SOHz

TU72-E

Hard-copy Equipment

LPIO.fE. LPIQ--FE
LPlMF. LPIO-FF
LPIO'HE, lPIQ-HE
LPlcrHF, LP1Q-HF
LPlMA. LPlcrFB
LPlMC. LPIQ-FD
LPlQ-HA, LPIQ-HB
LPl().HC, lP1crHD
LP1ocrBA .LPIOD-BB

XY10. XYtO
XYIo-A. XYtO·A

o
o

XY1O-8. Xyo-B

Actler . CALCO M P M odel 563 plotler wi th con lrol :
uses 3hnch paper, specI fy Slep size
Steps/ m inute
Slepslze
12.000
001 Inches
18,000
005 Inches
18,000
01 InChtlS

Optio n Designator
115V/60Hz 230V /50Hz

DESCRIPTION

Prerequisite

Maximum No.
SuppOrted
(Note 1)

Asynchronous Data Communication Systems
DCI(}AA,DC1(}AB
Data Line Scanner: provides controller plus four
units of cabinet space: DClO System handles up to
64 lines per oClO-A.

KA1O, KilO

oClO-B, oCl(}B

Eight-line Group: Interface for eight local or
dial-up lines; requires one unit of cabinet space:
dial-up lines require oCl0-E for full modem control.

DC1D-A

DC10-C, DC10-C

Telegraph Relay Assembly : provides conversion
from local to long lines using full - or half-duplex
facilities; requires two units of cabinet space.

DCI(}B and DC1(}O

DC10-D,DC10-D

Telegraph Power supply: pro .... ides a standard linevoltage power supply used with DCIO-C (120 volt,
2 amps): no cabinet space required.

DC1D-C

DC10-E,DC10-E

Expanded Data Set Control; provides expanded
DClO-B
control of eight data sets in the oCl0; recom mended for maximum system security; requires two
units of cabinet space.

oClO-F, DC10-F

Expander Cabinet; provides eight units of cabinet
space and power supplies for expansion beyond
DC1D-A.

oCI(}A

DC10-H, DC10-H

Eight-line Group; interface for eight local or dialup 2741-type lines; requires one unit of cabinet
space; dial-up lines requ ire OC1D-E for full modem
control.

OC1D-A

OAS80-AA, DAS80-AB

Remote Batch Station. Includes 1 ON81 -H,
lA36 Console, DAS80-CAlCB, DAS80-LNLB,
POP-l1 and software.

OAS 85. oN87. or
DC75NP

NJA

DAS81 -AA, DAS81-AB

Remote Concentrator. Includes PDP-It I DN81-H,
oAsa5, ON87, or
DN81-EA and software. Can add one more ON81 -EC. OC75NP
EO for a total of 32 asynchronous lines. ON81-Fx
asynchronous interfaces are also required and must
be ordered separately.

NJA

DAS82-AA, DAS82-AB

Remote Batch Station and Concentrator. Includes
PDP-II, OAS80-CA/CB card reader, DAS80-LA/LB
line printer, 1 DN81-H. DN81-EA and software.
DN81-Fx asynchronous interfaces are also
required and must be ordered separately.

DAS85, DN87, or
DC75NP

NJA

DAS92-AA, DAS92-AB

Includes 16K POP-81A processor, vr52. ROM for
down-line loading, one synchronous line interface.

oECsyslem-1O
DC75-NP, DAS85
or DN87

NJA

OAS92-EA

Asynchronous 4 line multiplexer including line
drivers. Will accommodate either 20 mA or EIA
lines in any mixture.

See DAS92
confrgurator

oAS92-CA, DAS92-CB

Card Reader for 8O-column (only) cards;
operates at 285 cpm.

See DAS92
contigutator

OAS92-PA, oAS92-Po

lA 180 Printer operates all80 cps and uses a
96-character set.

DAS92-VA, OAS92-VD

See DAS92
configurator

LP05 Line Printer (64 characters) operates at
300 Ipm ; 132 columns w ide carriage

DAS92-WA, oAS92-WD

See OAS92
configuralor

lP05 Line Printer (96 characters).

See DAS92
configurator

8
Note S

Remote Stations

Option oellgnlltor

Unit RecOrd Options
oAS8>CA. OAS8()-{:B
0/.S8><A. OASBO-LB

DESCRIPTION

Card Reader, 300 cards per minute.

CASSO Series Remote

Printer, 300 lines per minute, 132 printing pOSitions,
64 pnntlng characters, ECP character set.

CASSO Series Remote

Pnnter, 230 hnes per mmute, 132 printing positions,
96 printing characters, EoP character set.

CASSO Series Remote

ONS7 Including o110-C port only. Requires C110-A
With available port. Requires addition of CN81-xx
synchronous andlor asynchronous line options.

KAIO, K110, K110
CLlO

OH87·M, DN87-AB

oNS7 includmg o110-A Communications Interface
and one oL10-C port. Requires addition of CN81-xx
synchronous and/or asynchronous line options.

KAtO, KIt O, KL10

OH87S-M, DN87S-AB

ONS7 With oTE1O interface. Requires addition of
DNSHlx synchronous andlor asynchronous line
options
OC76 to DNS7 software only upgrade (including
KGII-A) .

1090

OC76

NfA

ONS7,87S·

ONS7, B7S·

ON87,87S

NfA

ON87,87S

NfA

ON87,87S

NfA

oNS7,87S

NfA

OAS8H-C. OAS80.ll)
Front Ends
DN8H)A, CN87·0B

ON87oU

AsyndvonooI Une Option'
Asynchronous Expansion Cabinet including one
DN81-EA. DN81·EB
ON81-EC 16-Llne Asynchronous Expansion Group.
Requires two oN81-Fx B·lIne Terminator Groups
to actIVate the hnes
DN81-€C, ON81-EO

0Ii8HA

DN81fS
DN81fC
ON81fD

Asynchronous IS-Line Expansion Group. This
reqUires two ON81-Fx B-Llne Termmators 10
acllvate the lines
Sollne Terminators each with 20 rnA Current
loop Local Interfaces.
B-Une Terminators each with EIA Local
Inlerfaces
B-Une Terminators each with EIA Full Modem
Control Interfaces.
Boline Terminators with Integral Auto Answer
Modems (These modems require customer
supplied oAA'S) .

Srncnronoul line Options
DN81-EE. DN81-EF
ON81-11

DN81-J

Synchronous Expansion Cabinet. Includes
one oN81 -H
Synchronous Single Line Controller Expansion
line For data transmission speeds of up to 10K
baud and for attachment to EIA RS232C
compatible modems.
Synchronous Single Lme Controller. For data trans'
miSSIOn speeds of up to 40.8K baud and for
attachment to 303-type current mode modems.

·Used on ON87, CNB7S Front Ends and on CASSO Series Remote Stations.

Prerequisite

Maximum No.
Supported
(Note 1)

ON87,87S
ON87,87S

CAS SO, B1. 82

ON87,87S

OASSO, Bl, 82

Option Designator
115V/ 60Hz 230V / 50Hz

DESCRIPTION

Prerequisite

Maximum No.
Supported
(Note 1)

IBM DEVICE EMULATION AND TERMINATION FRONT ENDS
DAS61 -DA. DB

IBM 2780 and/or 3780 Emulation and Termination
Front End. Including DL10-C port and requiring
D110-A with available port Requires addition of
DAS61-H andl o r DAS61-J synchronous line units.

KilO, Kl1 0, Dl10
TOPS106.03

DAS61-SA. SB

IBM 2780and/or 3780 Emulation and Termination
Front End including DTE10 interface. Requires
addition of DAS61-H andl or DAS61-J synchronous
line units.

KL10B

OAS61 -EA, EB

Synchronous Expansion Cabinet for expansion past
4 synchronous lines. Includes no synchronous lines.

DAS6l -D.DAS61-S

DAS61 -H

Synchronous Single line Controller for data
transmission speeds of up to 10K baud and for
attachment to EIA RS232C compatible modems.

DAS61-J

Synchronous Single line Controller for data
transmission speeds of up to SOK baud and for
attachment to 303-type current modems.

DAS61-0, DAS61-S

DAS61-D . DAS61S

DAS61-D, DAS61-S

Note 6
Note 6

DAS61 -QC

DAS61 Software Only

DAS61-QX

DAS78 to DAS61 Software Only Upgrade
(prerequisite GALAXY).

OAS62-DA, DB

IBM 2780 and/or 3780 and/or HASP mu lti-leaving
work station Front End. Including DLlD-C port and
requires DL1D-A with available port. Requ ires
addition of DAS62-H and/or DAS62-J synchronous
line un its.

KItO. KL 10, DL10
TOPS1O 6.03

DAS62-SA. SB

IBM 2780 and/ or 3780 and/or HASP multi-leaving
work station Front End including OTE10 interface.
Requires addition of DAS62+l and/ or DAS62-J
synchronous line units.

KL lOB

DAS62-EA. EB

Synchronous Expansion Cabinet for expansion
past 4 synchronous lines. Includes no synchronous
lines.

DAS62-D. DAS62-S

DAS62-H

Synchronous Single line Controller for data
transmission speeds of up to 10K baud and for
attachment to EIA RS232C compatible modems.

DAS62-D, DAS62-S

DAS62-J

Synchronous Single line Controller for data
transmission speeds of up 10 SOK baud and for
attachment to 303-type c urrent modems.

DAS62-D, DAS62-S

DAS62-QC

DAS62 Software Only.
DAS78 to DAS62 Software Only Upgrade
(prerequisite GAlAXY).

DAS62-D, DAS62'S
DAS78

Note 6

DAS62-QX

NoleS

OAS62-QY

OAS61 to DAS62 Software O nly Upgrade.

DAS6l

NoteS

LA36-CC. LA36-CD

OECwriler-lI; 3O-character-per-second teleprinter
with 20-mA current loop interface; handles up to
6-part forms. 132-column printing. variable-width
forms. 96 upper- and lower-case <;haraclers.

Asynchronous line

Note 4

LA37

APL-ASCII Terminal. 3O-character-per-second.
features full APL. full upper/lower case. or upper
case TTY cha racter sets.
Alphanumeric Terminal; 110 to 2400-baud CRT
display terminal; features 128-cha racter keyboard.
1440-character capacity screen. direct cursor addressing. 20-mA cu rrent loop or EIA interface.

DAS61-D, DAS61-S

Terminals

VTOSB-DA, VTOS-DB

Note 4

Option Designator
115V/6OH1.

230YJ5OH1.

Prerequisite

DESCRIPTION

Maximum No.
Supported
(Note 1)

GT40'AA, GT40-AB

Graphic System; computer-level graphic system
consisting 01 a graphical display system and
general-purpose mmicompu ter: features light pen.
128-character keyboard and EIA serial interface.

Note 4

VTSO-GA. VTSO-GD

DECscope; 75 to 9600-baud CRT terminal, 20-mA
current loop Interface. 9OO-character capacity
screen. 64-character keyboard.
OECscope: 75to 9600·baud CRT terminal. EIA
Interface. 1920-character capacity screen,
96-character keyboard.
DECscope; 75 to 9600-baud CRT terminal . EIA
Interface. 960-character screen. 64character keyboard
DECscope Video Display Block-mode Terminal;
1920-character display and full ASCII keyboard;
t28-character 7x8 dot matrix character set.

Note 4

VT52

VTSO·EA. VTSO-ED

VT.,

Note4

Note 4

Note 4
Note 6

Miscellaneous
DAtO.DAIO

Interface between KAtO or KltO CPU and PDP-8
minicomputer.

KAIO. KilO, KltO

01.

OKIO,DKtO

Real-time Clock; provides resolution to 10 microseconds via crys tal oscillator.

KAIO. or KltO

PClG-C

High speed paper tape readerl punch

KL10

GP10, GPIO

General Purpose Interface; provides interface to
KAl0 or KilO 1/0 bus; includes cabine t. two model
728 power supplies. one model 844 power control
indicator in panels. convenience outlet and
aSlo-A-15 cablet set; logic provides a status
register. device decoding. read-in gating and line
buffering.

KAIO. KilO. KlIO

N/A

GPtO-L, GP1o-L

GPIO Interface l ogic: interface logic only ; does
not include power su pply or indicators.

KAla. KilO. KlIO

N/A

GPtO-M. GPlO-M

GPIO less logic; includes power supplies and indicators; does not include cables.

KA1O, KilO, K110

N/A

DF01-AA, DFOI-AB

Acoustic Telephone Coupler.

OECsystem-IO
Terminal

Note 4

CAB-98 . CAB-9B

Cabinet: includes full-length single doors, Iront and
back with indicator panel, but without end panels
(old style).

OECsystem-l 0

N/A

H-956. H-956

Cabinet ; includes full-length single doors, front and
back with indicator panel. but without end panels
(new style).

DECsystem -l 0

N/A

Note: Specifications subject to change without notice.
Note 1

Maximum number supported by standard software. Configurations with large numbers of disk drives.
high-speed magnetic tape drives and/or data communication lines must be reviewed by OECsystem-l 0
Marketmg.

Note 2:

Maximum memory capacity of KAtO is 256K words in 16 memory modules. Maximum memory capacity
01 KilO or KL to is 4,096K word s in t6 memory modules.

Note 3:

Currently under software development. Contact DECsystem-l 0 Marketing before configuring.

Note 4

DECsystem-l0's support a maximum of 512 simultaneously-active terminals through t27 simultaneouslyactive jobs.

Note 5'

Software Supported by Computer Special Systems.

Note 6

Software Supported by Advanced Systems Group.
57

DECsystem ·10
UPGRADE/MIGRATION
PATHS
This chart illustrates the migration of

different DECsystem-10 subsystems
toward the common TOPS-10tTOPS20 hardware system . The chart is useful for determining what equipment is
supported within each OECsystem-10
family member. It also provides insight
into what equipment needs to be upgraded in moving from one CPU-based
system to another.

1090 EXTENDED

"60
1010

"MO
SYSTEM
DESIGNATION

""
""

"'"

HAROWARE FOR

TOPS -IO

TO PS·1O

' - TOPS-20

KltO

KlI06

Klt06 EXTENDEO

"60

1077

FUllY CO MPATIBLE

TOPS-tO OR TOPS -20
TOPS -IO

OPERATING

SYSTEM

TOPS ' IO

TO PS-IO

CPU

<A"

Ki l O

MA,O
ME M ORY

MEIO (161<)

MAIO'
MEIO

MF10(32K)

MFIO

MG10 (128K)

M G10
MH1 0 (2 561<)

RP1 0IRP02-3

RP1QIRP02-3
RHIOI RP04 & 06
RCIOIRM-flDIO

DISK

COM M UN ICATIONS

MAGTAPE

UNIT
RECORD

OC I O
DC76
DAS7S

TMIOAITUXX
TM IOITUXX

RH1OJRP04 & 06
RCIOIR M-RO I O-----4-

DCIO
DC76
DAS8S

MElD

ME10 -..>

M F10
M G10
M H10

MF10
MG10
M H10

M G10
MH10

RP 1OJRP02 "-3 ".."
RHIOIRP04 & 06
RHIOIRS04 - - 4

RH 1OJRP04 & 06 _
RH20IRP04 & 06

RH2OIRP04 & 06

CNa7
CN8 7S

CN87S

MFIO

DCIO· - , : ................

DO.
ON 67

TM IOAITUXX _______ ,

TC101TSU 43

TM 10BfTUXX
RH101TU 16
OX101TU7X
TC1 01TSU43

8A1 OJDEVICE

8A101DEVICE

TM lOOfTUXX
RHIOITU I 6 _
DXIOITU7X

RH2OiTU16
OX101TU7X
DX20ITUXX

,,/

8A1 010 EVICE

NOTES
1 N. w mlcfOC~ . TOps·20 R.......
2 Dfop ..... uPQf.d. f.pll<;.m.n l (old compo ..... l lypb. y f.luMldlrllio'Id)
3 Field "lfO llt llf1-PIac"
, Subll,IU llon 01 RH20 10' DFIOIRHIO
5 Filld Up\I"d. f.pll<;. OLIO w,' 11 OTE connec lion. SIW R......
6 F"'d UP\lf.d.' ... dd,' ion f,p"c"upg,.d. TMlOA w,'11 TMloa.M . dd OFI OIOFIO-C
7 l .pe Ch,nn" ,.p.I. CId willi OX20 lm'lfn.' ch.nn.')
6 8""0 H"d COP1 Con lfOI Unit "pl'C' d w,III POp·IH••• 1d con lfO"<1',
• SI.ffe<! 11.m'.ft 11>0.. hafd w. " comPOn.n'" wlllCft 'f' fIOt m.nu lactu,e<! . d,lticulll""POu _
1.lIu, .. w lllc;lI • •• nlUIUy ml k. Ih." IUPPO<1 uneconom lC"

6A1 010 EVlCE

RH2OITU16

"-....

DX2Of1'UXX

pop -" FRONT ENO
DEVICES

10 I<Ipport. 0< wl'lO" l ua:.U O' I)fOwod. . COlllpetto ..... ~ '" 0 _

ALGOL

AID
The Algebraic Interpretive Dialogue,
AID, is the DECsystem-l0 adaptation of

the language elements of JOSS, a program developed by the RAND Corporation. To write a program in the AID

language requires no previous programming experience. Commands to
AID are typed in via the user's terminal
as imperative English sentences. Each

command occupies one line and can
be executed immediately or stored as
part of a routine for later execution.
The beginning of each command is a
verb taken from the set of AID verbs.
These verbs allow the user to read,store
and delete items in storage; halt the
current processing and either resume
or cancel execution; type information
on his terminal; and define arithmetic
formulas and functions for repetitive
use that are not provided for in the
language. However, many common
algebraic and geometriC functions are
provided for the user's convenience.
The AIO program is device-independent. The user can create external files
for storage of subroutines and data for
subsequent recall and use. These files
may be stored on any retrievable storage
media, but for accessibility and speed,
most files are stored on disk.

• Programs may comprise separatelycompiled procedures
• Assignments are permitted within
expressions
• Remainder operator
• Unique Implementation of dynamic
own arrays
• Octal boolean constants and integer/boolean and boolean/integer
transfer functions
• Alternative reserved delimiter word
or ~quoted delimiter word" representations
The DECsystem -l0 ALGOL system
is based on the ALGOL-50 specifications. It is composed of the ALGOL
compiler, and the ALGOL object time
system. The compiler is responsible for
reading programs written in the ALGOL
language and converting these programs into machine language. The user
may specify a parameter at compile
time which produces a sequence num bered listing with cross-referenced
symbol tables.
The ALGOL object time system provides special services, including the
inpuUoutput service for the compiled
ALGOL program. Part of the object time
system ALGOL library is a set of routines
that the user's program can call in order
to perform various functions including
mathematical functions and string and
data transmission routines. These routines are loaded with the user's program
when required ; the user need only
make a call to them. The remainder of
the object time system is responsible
forthe running of the program and providing services for system resources,
such as core allocation and management and assignment of peripheral
devices.
Source level, interactive debugging
is provided through ALGDDT. The user
may stop his program at any point, may
examine and change the contents of
data locations. may insert connected
code and then continue execution to
test his changes.
60

APL
APL (A Programming Language) is a
concise programming language specially suited for dealing with numeric
and character data which can be collected into lists and arrays.The conciseness with which APL expressions can
be written greatly enhances programmer productivity and allows fo r very
compact and readable code which can
be executed in a highly efficient manner.
APL finds application not only in mathematics and engineering, but also in financial modeling and text handling
situations.
Some of APL's features include:
• The user's active workspace size is
dynamically variable
• The workspace symbol-table is dynamically variable
• Immediate-mode line editing at complex APL expressions
• Statement branching may occur
anywhere in a statement line
• Multiple statements may appear in a
single line
• User-controlled tab positioning for
110 operations
• All floating point operations are performed to an accuracy of eighteen
decimal digits
APL is a fully interactive system with
both immediate (desk calculator) and
function (program) modes of operation.
It includes its own editor as well as debugging tools, tracing ot fun ction execution , typeout of Intermediate values,
setting break points. etc. APL for the

BASIC
• Multiple users share the BASIC compiler's pure code.
• A variety of program manipulation
commands which include functions
for savings, running and retrieving
BAStC programs
• Immediate mode statements to fa cilitate debugging and ~desk calculator ~ mode
• Sequential data storage
• String capability; including string
arrays and functions
• Chaining with COMMON to accommodate large programs
• Formatted output using the PRINT
USING statement

DECsystem-l0 Includes many extensIOns not normally found in other APL
Implementations Some of these features Include a fleXI~ file system which
supports both ASCII sequential and
~nary direct access files, the dyadic
format operator, expanded command
formatIOns which allow the user to take
advantage of the DECsystem -10 fite
system , the execute operator and tools
for error analysis and recovery. In additIOn, workspaces are dynamically variable 10 sizes up to 512K bytes and the
system su pports double precision calculations which allow up to 18 decimal
digIts of precisiOn
FlnallY, APLon the DECsystem -lOis
available to all users at all times without
the need to run a separate subsystem
which provides extra terminat handling,
workspace swapping, etc. These tasks
are all accomplished by the TOPS-10
operating system

BASIC is a conversational problem
solving language that is well suited for
timesharing and easy to learn. It has
wide application in the scientific, business, and educational communities
and can be used to solve both simple
and complex mathematical problems
from the user's terminal.
The BASIC user types in computational procedures as a series of numbered statements that are composed
of common English terms and standard
mathematical notation. After the statements are entered, a run-type command
initiates the execution of the program
and returns the results.
If there are errors during execution,
the user, from his terminal, simply
changes the line or lines in error by
deleting, modifying, or inserting lines.
The beginning user has many facilities at his disposal to aid in program
creation:
• Program Editing Facilities-An existing program ordata file can be edited
by adding or deleting lines, by renaming it, or by resequencing the
line numbers. The user can combine
two programs or data files into one
and request either a listing of all or
part of it on the terminal or a listing
of all of it on the high-speed line
printer.
61

• Documentation Aids-Documenting
programs by the insertion of remarks
within procedures enables recall of
needed information at some later
date and is invaluable in situations
in which the program is shared by
other users.
• As a BASIC user, you can type in a
com putational prodedure as a series
of numbered statements by using
Simple common English syntax and
familiar mathematical notation. You
can solve almost any problem by
spending an hour or so learning the
necessary elemenlary commands.
• Functions-Occasionally, you may
want to calculate a function, for example, the square of a number. Instead of writing a program to calculate this function, BASIC provides
function s as part of the language.
More advanced users will want to
take advantage of some of the more
sophisticated computation and data
handling tools which BASIC provides.
For example:
File Input -The user may create a
name date file using the BASIC editing
fa cilities.This file may now be referenced.
within a program.
Output Formatting -The user can
control the appearance of his output
to the terminal or printer.
Data Access-Data files may be read
facilities. This file may now be referenced
and written either sequentially or randomly.
String Manipulation - Alphanumeric
strings may be read, printed, concatenated and searched.

COBOL
The COmmon Business Oriented
Language, COBOL. is an industry-wide
data processing language that is dedesigned for business applications,
such as payroll, inventory control, and
accounts receivable.
Because COBOL programs are
written in terms that are familiar to the
business user, he can easily describe
the formats of his data and the processing to be performed in simple
English..Jike statements. Therefore, programmer training is minimal, COBOL
programs are self-documenting, and
programming of desired applications
is accomplished quickly and easily.
Major features include:
• On-line edit ing and debugging-The
programmer may create and modify
the source program from a terminal
using an easily-learned editing facility. After the program has been submitted to the compiler-again from
the terminal-any syntax errors may
be immediately corrected using the
editor, and the program resubmitted.
The program listing is sequence
numbered with symbols cross-ref'
erenced to show when they are
defined and where used. COBOOT,
the on-line, interactive COBOL debugging package, allows the programmer to check out the program:
• By selectively displaying a paragraph name
• By causing the program to pause
at any desired step during execution
• By allowing the program to examine and modify data at will before continuing execution
Easy program devetopment and debugging increases programmer productivity by eliminating tedious waiting periods.
• Batch
Using the same commands for timesharing, the programmer may submit the program via a control file to
the Batch system. This further increases efficiency because other
terminal work may be done concurrent with the Batch processing
• Access Methods
The programmer has a choice of
three access methods; sequential,
indexed sequential, and random.

Indexed Sequential
Access Mode (lSAM)
ISAM requires a minimum amount
of programming while providing a large
data file handling capaCity. It is supported by the COBOL Object Time
System which automatically handles all
of the searching and movement of data.
All reading and writing of an index
file (ten levels of indexing) are performed by the run-time operating system (lIBOL). This does not involve the
user. When using the indexed sequential files, the programmer need only
specify which record is to be read,
written, or deleted.
Whenever records are added to the
file, the index is automatically updated.
additions to the file will not degenerate
the file as with other computers. The
common technique for using overflow
areas for added records has been
avoided. Whenever record s have been
deleted from the file, the empty space
is used again for later additions. The
net effect of the addition and deletion
techniques significantly increases the
time between major ·overhauls ~ of Ihe
data files, because the time required
to access a file is independent of the
number of changes made to It.
• Sorting
The SORT package permits a user
to rearrange records or dala according 10 a set of user-speCified keys.
The keys may be ascending or de·
scending, alpha or numeric, and any
size or location within the record.
Mufti-reel file devices may be specified.
• Source Ubrary Maintenance System
This system lists file entries or adds,
replaces, and/or deletes source language data on a file. It can also add,
replace, or extract an entire file from
the library.
• Device Independence
The operating system allows the programmer to referen ce a device with
a user'assigned logical name as well
as its physical name, thus allowing
dynamic assignment of peripheral
devices at run time.

CPL
CPL is an interpreter supporting a
subset of the draft ANSI PUI language.
The following is a summary of the key
features of CPl:
• Data types include FIXED, FLOAT,
CHARACTER. CHARACTER VARYING, BIT VARYING, POINTER , and
arrays of Ihese data types.
• Storage classes include AUTOMATIC, STATIC, CONTROLLED and
BASED
• Almost all PUI statement types are
supported including READ, WRITE,
DECLARE, DEFAULT, GET, PUT, ON
and FORMAT
• Subroutines and function procedures
are recursive
• The ON statement provides the
capability of recovering from program error under program control.
• Complete string manipulation package
• CPL supports the following classes
of PUI built-in functions: arithmetiC,
mathematical, string array, storage
control and pseudo-variables.
CPL is intended to be easy-to-use for
the beginning programmer or non-programmer. At the user's option, state'
ments will be executed immediately or
saved for deferred execution. A begin+
ning programmer can start by executing simple computational statements
and can proceed to building programs.
Since CPL is an interpreter, a user can
track a program very closely. Debug ·
ging features, such as source level
breakpoints and program modification
are available.

FORTRAN
Version It
FORTRAN-tO is a superset of the
American National Standard FORTRAN. Both the compiler and objecttime system are reentrant (shareable).
The compiler produces optimized object code. The following is a summary
of key features and extensions of FORTRAN-tO:

• Data Base Management System
Interface
The programmer may call upon the
data base management system faCilitieS from within his program . This
system . which allows the CODASYL
specificatIOns. allows data files to be
consolidated Into one or more data
bases Application programs are
then permitted to access the dala
In the way best suiled to their needs.

FORTRAN
The FORmula TRANslator language.
FORTRAN . IS a widely-used and precedul~nented programming language.
It IS designed for solving scientific problems and IS thus composed of mathemabcal-llke statements constructed in
accordance with precisely formulated
ruies. Therefore. programs written in
FORTRAN consist of meaningful sequences of these statements that are
.ntended to dllect the computer to perfOl"m the specified computations.
FORTRAN has a wide use in every
segment of the computer market.
UniversitIeS fmd that FORTRAN is a
good language with which to teach
students how to solve problems via the
computer The scientific community
relies on FORTRAN because of the
ease with which scientific problems
can be expressed In addition. FOR TRAN IS used as the primary data processmg language by many timesharing
ul ties.

• PARAMETER statement- Allows symbolic specification of compile-lime
constants
• INCLUDE statement-Allows user to
include in the compilation of a given
program unit source code which resides on a file other than primary
source file
• GLOBAL OpnMIZAnON-FORTRANto performs extensive local and optional global optimizations
• FORDDT -the FORTRAN-tO debug-

ge,
FORDDT in conjunction with the
FORTRAN-l0/~DEBUG M switch will
allow:
• Display and modification of program data
• Tracing of the program statement
by statement
• Setting of pauses on any statement or routine
• OPEN/CLOSE file-specification statements
• Array bounds checking can be generated optionally
• N-dimensional arrays
• ENCODE/DECODE statements
• Boolean operations equivalence
(EOV) and exclusive or (XOR), in
addition to OR. AND. NOT.
• The NAMELIST and list-directed 110
features provide format-free input
and output operations
• Random-access 110 capabilities
• Compatibility with IBM type declaration statements
• Implied DO loops in 110 statements
and data statements
• Full mixed'mode arithmetic in expressions
• Octat Constants
• Logical Operations-full-word masking operations for aU logical functions
(rather than a result of just true or
false)
• END ::: and ERR = in 110 statements
• Device independence

The FORTRAN-tO object-time system, FOROTS. controls the input/outpul, format interpretation and numerical conversion for compiled programs.
The FORTRAN user may reference any
110 device. All special editing. conversion. and file structuring tasks are
handled by the object-time system. Devices are normally specified by logical
assignment so that physical device
selection need not be made until runtime. The devices corresponding to the
special 110 statements READ. PRINT.
ACCEPT. and TYPE are also assignable
at run -time. The object-time system is
shareable.
FOROTS implements all program
data file functions and provides the
user with an extensive run-time error
reporting system. Device independence
is provided to allow the programmer
or operator to determine the physical
device at run-time.
FORTRAN-tO is easy to use in both
timesharing and batch processing environments. Under timesharing . the
user operates in an interactive editing
and debugging environment. FORDOT.
an interactive program that is used as
an aid in debugging.
FORTRAN programs uses the language
constructs and variable names of the
program itself-thereby eliminating the
need to learn another language in order
to accomplish on-line debugging. Under
batch processing. the user submits his
program through the batch software
in order to have the compiling. loading.
and executing phases performed without his intervention.
FORTRAN programs can be entered
into the FORTRAN system from a number of devices: disk. magnetic tape.
user terminal and card reader. In addi·
tion to data files created by FORTRAN.
the user can submit data files or FORTRAN source files created by the system editor. The data files conlain the
data needed by the user's object program during execution. The source files
contain the FORTRAN source text to
be compiled by the FORTRAN compiler. Output may be received on the
user's terminal. disk or magnetic tape.
The source listing cross references all
symbols to show where they are defined
and where used.

MACRO
MACRO is the symbolic assembly
program on the DECsystem-1O.1t makes
machine language programming easier
and faster for the user by
• Translating symbolic operation codes
in the source program into the binary
codes needed in machine language
instructions.

• Relating symbols specified by the
user to numeric values.
• Assigning absolute core addresses
to the symbolic addresses of program instructions and data.
• Preparing anoulputlistingoflheprogram which includes any errors detected during the assembly process.
MACRO programs consist of a series
of statements that are usually prepared
on the user's terminal with a system
editing program. The elements in each
statement do not have to be placed in
certain columns nor must they be separated in a rigid fashion. The assembler
interprets and processes these state·
ments, generates binary instructions or
data words, and performs the assembly.
MACRO is a two-pass assembler.
This means that the assembler reads
the source program twice. Basically, on
the first pass, all symbols are defined
and placed in the symbol table with
their numeric va lues, and on the second
pass, the binary (machine) code is gen·
erated. Although not as fast as a one·
pass assembler, MACRO is more efficient in that less core is used in
generating the machine language code
and the output to the user is not as long.

MACAO is a device-independent
program; it allows the user to select, at
runtime, standard peripheral devices
for input and output files. For example,
input of the source program can come
from the user's terminal, output of the
assembled binary program can go to a
magnetic tape, and output of the program listing can go to the line printer.
More commonly, the source program
input and the binary output are disk files.
The MACAO assembler contains
powerful macro capabilities that allow
the user to create new language elements. This capability is useful when a
sequence of code is used several times
with only certain arguments changed.
The code sequence is defined with
dummy arguments as a macro instruction . Thus, a single statement in the
source program referring to the macro
by name, along with a list of the real
arguments, generates the entire correct
sequence. This capability allows for the
expansion and adaptation of the assembler in order to perform specialized
functions for each programming job.
64

SORT
The TOPS-lO SORT arranges the
records
one or more files according
to a user-specified sequence. The user
designates the keys on which the records are sorted from one or more fields
withlO a record. The keys can be ineither
ascenchng or descending order. SORT
compares the key 'Ields values of all
'ecords Then rt arranges the records
on the speCified sequence and merges
them Into a single output file. Sort may
be used under timesharing and batch,
and may be called from within a COBOL
program.

Data Base
Management
System
Certam data-such as that within
commercial, aecou nling. inventory control and admInistrative systems-are
used In computer applications which

na... e common relationships and proces5lng reqUIrements with data in other

apphcabOns ThIs can prove to be a
prob4em because as file organizations
are defined In one application or program, restructuring, redundant appearance. and even repetitive processing of
:he same data are often required in
another apphcallOn.
To further complicate the problem ,
oo ... ne processes (i_e., customer order
entry, shipment planning, and student
"formabon retrieval systems) tend to
d Herent data structures than the processes used to create and maintain
pnmary data flies. This means that as
new apphcabons requirements for ex~t.lOg data are determined and additonal data are defined, program development personnel must either alter existIn9 data file forms and programs or
create and mamtaln redundant copies.

DIGITAL offers a solution to the
problem in the Data Base Management
System-DBMS. It enables DEC system-l0 users to organize and maintain
data in forms more suitable to the integration of a number of related but
separate processes and applications.
DBMS is ideal in situations where data
processing control and program development function s require structu res
and techniques not satisfied by traditional data management facilities.
Features
The DECsystem-l0 Data Base Management System is predicated upon
the proposals of the CODASYL Data
Base Task Group (oBTG) which appear
in their report of April. 1971. DIGITAL's
goal for DBMS is to provide features
which assist users in obtaining the most
significant objectives stated in the
COoASYL oBTG report. These features
include:

• Hierarchical Data Structures
-In addition to sequential structures,
simple tree structures and more
complex network structures can be
created and maintained. Data items
can be related within and between
various levels 01 the structure established.

( ttAIN

II
ow><.

;'I
,

~
p MtMaEA

iftMtM9lA

Iil'N

II
N ' NEU POINTU
, . 1'11I0Il IOINlEt

o· OWNfA I'OINTEfi
• Non-redundant Data OccurrenceData items may appear in a number
of different structural relationships
without requiring multiple copies of
the data. Data structures may be
established and modified in a manner most suitable to a given application without altering the occurrence
of the data in structures maintained
for other applications.
• Variety of Access and Search
Strategies-Data records can be
maintained in chains, as illustrated
below. Access may be through
DIRECT, CALCULATED, or VIA set
location modes. Sort keys, in addition to the normal storage key, may
be defined.
• Concurrent Access-Multiple run
units (or programs) that use the
same re-entrant code module further
DECsystem-tO
supplement the
monitor's extensive centralized file
handling capabilities. Any number of
concurrent retrievals to the same
data areas can be handled. Concurrent updates to the same area
can be handled by a multiple update
queuing mechanism.
• Protection and Centralized Control
-Usage of a common data definition
language establishes data base structures maintained on direct access
storage devices that are selectively
referenced by individual application
programs through privacy lock and
key mechanisms. Physical placement of data is specified by a centrally-controlled data definition processor.

• Device Independence-The common input/output and control conventions of the DECsystem-l0
monitor provide basic device independence. Applications programs
deal with logical areas rather than
physical devices. Data base areas
may reside on the same or different
ITPS-l0, In-House Text Preparation
direct access storage devices as
System allows DECsystem-l0 users to
non-date base files.
prepare office-quality or camera-ready
• Program Independence of Data(typeset) copy using the interactive
Significant steps toward program
capability of the DECsystem-1Q. Highindependence are ach ieved by using
quality, camera-ready copy for pamthe SCHEMA and SUB-SCHEMAconphlets, advertising brochures, product
ceplS of data definition. Individual proflyers, user manuals, and many other
grams reference only user-selected
types
of documentation can be produced
data elements rather than entire recand
updated
rapidly and inexpensively
ord formalS. Program alterations due
using ITPS-l0. The system allows use 01
to adding new data and relationships
many different input and output devices,
are minimized. Atterations of the origiincluding interactive CRT or hard copy
nal form (i.e., binary, display) and
terminals. line printers, typewriterlike
element sizes require program redevices,
and photocomposition equipcompilations.
ment
Documents
are stored as standard
• User Interaction Without Structural
DECsystem-l0
files
and can be easily
Maintenance Responsibilities - Inupdated, edited and re-generated.
dividual users, applications, and proThe system is easy-to-use and easy
grams may access data structures
to
learn. Current successful applicawithout the responsibility of maintions range from preparing form letters
taining detailed linkage mechanisms
to setting daily newspapers.
that are internal to the data base
software. Common and centralized
authorization, error recovery, and
building techniques reduce individual
LINK-tO, the DECsystem-l0 linking
activity to maintain data structures.
loader. merges independently-translated
• Muttip6eLanguageUsage-TheDBMS
modules of the user's program Into a
data manipulation language is availsingle module and links thiS module
able to both COBOL and FORTRAN
with system modules into a form that
as host languages
can be executed by the operating sys• DBMS Software Modules Consistent
tem. It provides automatic retocabon
with the CODASVL
and loading of the binary modules proData Base Task Group report, the body ducing an executable verSion of the
of the DECSVSTEM-20 data base man- user's program. When the loading proagement software includes:
cess has been completed. the user can
request LINK-tO either to transfer con• DOL-data description language and
tralto his program for immediate exeits processor
cution or to output the program to a
• DML-data manipulation language
device for storage in order to aVOid the
fat COBOL and FORTRAN programs
loading procedure in the future .
• DCBS-data base manager module of
While the primary output of lINK-l0
re-entrant run-time routines
is the executable version of the user's
• OBU-group of data base system supprogram, the user can requestauxihary
port utilities

ITPS·10

LlMK·10

OIltpUt III the form of map, log, save,
symbol, overlay plot, and expanded
core linage files This additional output
IS not automatically generated: the user
t tnCIude appropriate switches in
tws com mand strings to LINK-10 in order
to oblalll thIS type of output. The user
can also gam precise control over the
tIaCJIng process by setting various load~ parameters and by controlling the
Il'I9 of symbols and modules. FurlIermofe. by setting switches in his
command stnngs to LINK-tO, the user
r.I specdy the core sizes and starting
dtesses of modules, the size of the
s,mboI tab6e, the segment into which
'lne symbol tab6e IS placed, the messages
It'Ie
see on his terminal or in his log
the seventy and verbosity levels
oI\1'Iemessages . Finally, he can accept
. . UNK-K) defaults for items In a file
$PedfJCahon or he can set his own defICIts that 'NIII be used automatically
wnen he omits an Item from his commiI'Id stnng
1(-10 has an overlay facility to be
used when the total core required by a
user s program IS more than the core
I¥a8bIe to the user. The user organizes
bel program so that only some portions
tfIe program are reqUired in core at
.". one llme The remaining portions
:resde '" a dISk file and are transferred
~ out of core during execution.
Because the porttOn brought into core
may over1ay a portion already core~t. the amount of core required
D)' It'8entJfe program is reduced. Overtays can be invoked either by runtime
routines called from the user's program
Of by automatIC calls to subroutines
outsde the current overlay link.

".-1d

MACY11 - LNKX11
UolCYll IS a cross-assembler which
opetdtes on the OECsystem-IO and
as:sembles MACAO-ll source code for
t'Ie POP-It family of computers.
MACYll will produce 8IIher an absoe binary or a relocatable object modIAe depending upon the assembly
mode The resultmg absolute bmary
files are transferrable to the PDP-ll for
executJOn or, the relocatable object
modules may be used as Input to the
11 'mker on the OECsystem-l0
and then transferred to the PDP-ll operahng enVIronment. MACYll will append a symbollable and (optionally) a
cross-reference table to the listing file.
IAA(;Yll produces a -s ide-by-side~ as5embly listmg of symbolic source statements, thetr octal equivalents, assigned
addresses and error codes.

DDT
The Dynamic Debugging Technique,
DOT, is used for on-line program composition of object programs and loran ·
line checkout and testing of these programs. For example, the user can
perform rapid checkout of a new program by making a change resulhng from
an error detected by DOT and then Immediately executing that section 01 the
program for lestlng.
Alter the source program has been
compiled or assembled, the binary object program with ItS table of defined
symbols is loadedwllh DDT. In command
stflngs 10 ~OT. the user can speCify
locations in hiS program, or breakpoints,
where ~OT is to suspend execution in
order to accept further commands. In
this way, the user can check out his program sectlon-by-section and.lfan error
occurs, tnsert the corrected code immediately. Either before DOT begins
execution or at breakpoints, the user
can examine and modify the contents
of any location. lnserlionsand deletions
can be 10 source language code or in
vaflous numeflc and texl modes. DDT
also performs searches, gIves cond.,
tlonal dumps, and calls user-coded
debuggtng subrouttnes at breakpoint
locations
67

FAILSAFE/BACKUP
The FAILSAFE/BACKUP programs
are used to selectively or universally
save disk files on magnelic tape. Files
may be copied to magnetic tape. In a
special format, selectively by hie name
or groups of file names, by projectlprogram mer number, by disk structure
(logical or physical), or universally In
addition to providing backup of files,
these programs allow a method of extendmg disk space by allowmg infrequentlY'used files 10 be stored on tape.
RestaTing of files from FAILSAFE/BACK,
UP formatlapes can likewise be handled
on an Individual file. groups of files,
projecllprogrammer, log.cal or phYSical
disk basis. An added benefit is achieved
when restOTing files in Ihat disk fragmentation is often minimized by the
failsafe /restore operation.

TECO

Message Control
System
The Message Control System (MCS~1O)
is to provide the DECsystem-l0 with an

efficient, transaction processing-oriented system that facilitates control of
communications between a network of
t erminals and applications processes.
The intent is to provide generalized routines that are readily used from COBOL
programs and network definitions. Message control in its fullest sense includes

a complex of hardware and software
systems:
• Terminals and transmission devices.

• Remote and central site concentrators.
• Central site communications multi•

plexers.
DECsystem-l0 Monitor and its Message Service module.

• Message Control System (MCS-l0)
•

Routines.
Extended Communications Language

module and interfaces (COBOU
lIBOl).
• Network Definition, Activation and
Operations Control Routines.
• Message Oriented Applications Programs.
• Data Base Management capability
via DBMS-1O.
The activities normally associated
with message control are cooperative
processes distributed among communications concentrators, multiplexers,
and a central system. Actual 110 transmission, line control, error handling,
device selection, code translation, and
message buffering are handled by the
remote and local concentrators and
front-end processors. The DECsystem10 central processor, Monitor, and Message Control modules accept, route,
queue and log term inal and application
program-generated messages. Upon the
occurrence of specific user-specified
events, application programs are activated to perform message processing.
Applications programs receive messages
from queues through interface modules,
perform processes related to data within messages and send messages back
through queues to terminals andlor
other application processes.

PIP
The Peripheral Interchange Program,
PIP, is used to transfer data files from
o ne 110 devjce to another. Commands
to PIP are formatted to accept any number of input (source) devices and one
output (destination) device. Files can
be transferred from one or more source
devices to the destination device as
either one combined file or individual
files. Switches contained in the command string to PIP provides the user
with the following capabilities:
• Naming the files to be transferred.
• Editing data in any of the input files.
• Defining the mode of transfer.
• Manipulating the directory of a device
if it has a directory.
• Controlling magnetic tape and card
punch functions.
• Recovering from errors during processing.

RUNOFF
RUNOFF facilitates the preparation
of typed or printed manuscripts by performing line justification, page numbering, titling, indexing, formatting, and
case shifting as directed by the user.
The user createsa file with an editor and
enters his material through his terminal.
In addition to entering the text, the user
includes information for formatting and
case shifting. RUNOFF processes the
file and produces the final formatted file
to be output to the terminal, the line
printer, or to another file.
With RUNOFF, large amounts of material can be inserted into or deleted
from the file without retyping the text
that will remain unchanged. After the
group of modifications have been added
to the file, RUNOFF produces a new
copy of the file which is properly paged
and formatted.

The Text Editor and COrrector program , TECO, is a powerful editor used
to edit any ASCII text file with a minimum
of effort. TECO commands can be
separated into two groups: one group
of elementary commands that can be
applied to most editing tasks, and the
larger set of sophisticated commands
for character string searching, text block
movement, conditional commands, programmed editing, and command repetition.
TECO is a character-oriented editor.
This means that one orm ote characters
in a line can be changed without retyping
the remainder of the line. TECO has the
capability to edit any source docu ment:
programs written in MACRO, FORTRAN,
COBOL. ALGOL, or any other source
language; specifications; memoranda,
and other types of arbitrarily-formatted
text. The TECO program does not require that line numbers or other special
formatting be associated with the text.
Editing is performed by TECO via an
editing buffer. which is a section within
TECO's core area. Editing is accomplished by reading te xt from any device
into the editing buffer (inputting), by
modifying the text in the buffer with
data received from either the user's
term inal or some other device (inserting),
and by writ ing the modified text in the
buffer to an output file (outputting).
A position indicator, or buffer pointer,
is used to locate characters within the
buffer and its position determines the
effect of many of TECO's commands.
It is always positioned before the first
character, between two characters, or
after the last character in the buffer.
Various commands, such as insertion
commands, always take place at the
current position of the buffer pointer.
There are TECO commands to manipulate data within the editing buffer.
Input and output commands read data
from the input file into the buffer and
output data from the buffer to the output file. There are other commands to
have one or more characters inserted
into the editing buffer, deleted from the
buffer, searched for, andlor typed out.
In addition. the user can employ iteration commands to execute a sequence
of commands repeatedly and conditional execution commands to create
conditional branches and skips.

TOPS-10
Operating System
The resident operating system is
made up of a number of separate and
somewhat independent parts, or routines. Some of these routines are cyclic
In nature and are repeated at every system clock interrupt (tick) to ensure that
every user of the computing system is
receMng the requested services. These
cyclic routines are
• The command processor, or decoder
• The scheduler
• The swapper
The command decoder is responsible
for Interpreting commands typed by
the user on his terminal and passing
them to the appropriate system program
or rouMe. The scheduler decides which
user is to run in the interval between the
clock interrupts, allocates sharable
system resources, and saves and restores conditions needed to start a program interrupted by the clock. The
swapper rotates user jobs between
secondary memory (usually disk or
drum) and core memory after deciding
which jobs should be in core but are not.
These routines constitute the part of
the operating system that allows many
jObs to be operating simultaneously.
The non-cyclic routines of the operatmg system are invoked only by user
programs and are responsible for providing these prog rams with the services
avaiable through the operating system.
These routines are
• The UUO handler
• The InpuUoutput routines
• The file handler

ecuted, go to the operating system for
processing. The input/output routines
are the routines responsible for directing data transfers between peripheral
devices and user programs in core
memory. These routines are invoked
through the UUO handler, thus saving
the user the detailed programming
needed to control peripheral Ctevices.
The file handler adds permanent user
storage to the computing system by
allowing users to store named programs and data as files.

Scheduler
The DECsystem-l0 is a multiprogramming system; i.e., it allows several
user jobs to reside in core simultaneously and to operate sequentially. It is
then the job of the scheduler to decide
which jobs should run at any given time.
In addition to the multiprogramming
feature, the DECsystem-l0 employs a
swapping technique whereby jobs can
exist on an external storage device
(e.g., disk or drum) as well as in core.
Therefore, the scheduler decides not
only what job is to be run next but also
when a job is to be swapped out onto
disk or drum and later brought back into
core.

------------1 1=1"

1
1
1L ____________
~~. -.11

The UUO handler Is the means by
which the user program communicates
with the operating system in order to
have a service performed. Communicatton is by way of programmed operators (also known as UUO 's) contained
In the user program which, when ex-

THE RESIDENT OPERATING SYSTEM.

All jobs in the system are retained in
ordered groupings called queues.
These queues have various priorities
that reflect the status of each job at any
given moment. The queue in which ajob
is placed depends on the system resource for which it is waiting and, because a job can wait for only one resource at a time, it can be in only one
queue at a time. Several of the possible
queues in the system are
• Run queues for jobs waiting for, or
jobs in, execution.
• 1/0 wait queues for jobs waiting for
data transfers to be completed.
• Resource wait queues for jobs waiting for some system resource.
• Null queue for all job numbers that
are not currently being used.
The job's position within certain
queues determines the priority of the
job with respect to other jobs in the
same queue. Forexampte, if ajob is first
in the queue for a sharable device, ithas
the highest priority for the device when
it becomes available. However, if a job
is in an I/O wait queue, it remains in the
queue until the 1/0 is completed. Therefore, in an li D wait queue, the job's poSition has no significance. The status of a
job is changed each time it is placed into
a different queue.
The scheduling of jobs into different
queues is governed by the system
clock. This clock divides the time forthe
central processor into sixtieths of a
second. When the clock licks, the
scheduler decides which job will run
during the next cycle. Each job, when it
is assigned 10 run, is given a time slice.
When the time slice expires for the job,
the clock notifies the central processor
and scheduling is performed. The job
whose time slice just expired is moved
into another, perhaps lower, priority run
queue, and the scheduler selects another job to run in the next time slice.
If the currently running job is the null
job and a higher priority job (any job)
becomes ready to run before the clock
ticks it will immediately run. If the currently running job is not the null job and
a high priority (HPQ real -time) job becomes runnable it will run at the next
clock tick. Finally if a job just becoming
runnable is not an HPQ job, but is of
higher priority than the current job, it will
only preempt the current job when the
applicable time slice has expired.

Each job, when it is assigned to run, is
given a time slice. When the time slice
expires for the job, the clock notifies
the central processor and scheduling
is performed. The job whose time slice
just expired is moved into another, perhaps lower, priority run queue, and the
scheduler selects another job to run in
the next time slice.
Scheduling may be forced before the
clock ticks if the currently-running job
reaches a point at which it cannot immediately continue. Whenever an
operating system routine discovers
that it cannot complete a function requested by the job (e.g., it is waiting for
110 to complete or the job needs a device which it currently does not have). it
calls the scheduler so that another job
can be selected to run. The job that was
stopped is then requeued and is scheduled to be run when the function it requested can be completed. For example : when the currentiy running job
begins input from a DEC tape, it is placed
into the 110 wait queue, and the input
is begun. A second job is scheduled
to run while the input of the first job
proceeds. If the second job then decides to accessa DECtape, it is stopped
because the DECtape control is busy,
and it is placed in the queue for jobs
waiting to access the DECtape control.
A third job is set to run. The input operation of the first job finishes, freeing
the DECtape control forthe second job.
The 110 operation of the second job is
initiated, and the job is transferred from
the device wait queue to the 110 wait
queue. The first job is transferred from
the 110 wait queue to the highest-priority run queue. This permits the first job
to preempt the running of the third job.
When the time slice of the first job becomes zero, it is moved into the second
run queue, and the third job runs again
until the second job completes Its I/O
operation.

In addition, data transfers allow the
scheduler to permit the user to overlap
computation with data transmission. In
unbuffered data modes, the user supplies an address of a command list containing pointers to locations in his area
to and from which data is to be transferred. When the transfer is initiated,
the job is scheduled into an I/O wait
queue where it remains until the device
signals the scheduler that the entire
transfer has been completed.
In buffered modes, each buffer contains information to prevent the user
and the device from using the same
buffer at the same time. If the user requires the buffer currently being used
by the device as his next buffer, the
user's job is scheduled into an 110 wait
queue. When the device finishes using
the buffer, the device calls the scheduler to reactivate the job.
TOPS-l0 also provides the ability to
tune the system scheduler to specific
loads. The system administrator can
set aside percentages of the CPU to
given classes of timesharing and batch
users. This facility can be dynamically
changed while the system is running
and need not be defined at system generator time, thus facilitating optimal
system usage over a wide variety of
system loads.

Swapper
The swap per is responsible for keepIng in core the jobs most likely to be run.
It determines if a job should be in core
by scanning the various queues in
whICh a job may be. If the swapper decides that a job should be brought into
core, it may have to take another job
already in core and transfer it to secondary storage. Therefore, the swapper
~ not only responsible for bringing a
JOb IOta core but is also responsible for
selecting the job to be swapped out.
A job is swapped to secondary storage
for one of two reasons:
• Ajob that is more eligible torun needs
to be swapped in and there is not
enough room in core for both jobs.
• The JOb needs to expand its core size
and there is not enough core space
to do so.
If the latter case is true, the job must
be swapped out and then swapped in
later with new allocation of core.
The swapper checks periodically 10
see .f a job should be swapped in. If
there IS no such job, then it checks to
see If a job is requesting more core. If
there IS no job wishing to expand its size.
then the swapper does nothing further
and relinquishes control of the processor until the next clock tick.

uuo Handler
The UUO handler is responsible for
accepting requests for services available through the operating system .
These requests are made by the user
program via software-implemented instructions known as program med operators, or UUO's . The various services
obtainable by the user program include:
• Communicating with the 1/0 devices
on the computing system, including
connecting and responding to any
special devices that may be desired
on the system for real -time programming.
• Receiving or changing information
concerning either the computing
system as a whole or the individual
program.
• Altering the operation of thecomputing system as it concerns the user
job, such as controlling execution by
trapping or suspending, or controlling core memory by locking.
• Communicating and transferring
control between user programs.
The UUO handler is the only means
by which a user program can give control to the operating system in order to
have a service performed . Contained in
the user program are operation codes
which, when executed, cause the hardware to transfer control to the UUO
handler for processing. The routine
obtains its arguments from the user
program. The core location at which the
UUO operation was executed is then
remembered. After the UUO request
has been processed, control is returned
to the user program at the first or second
instruction fOllowing the UUO . In this
way, the software supplements the
hardware by providing services that are
invoked through the execution of a
single core location just as the hardware services are invoked.
71

Device Service Routines
1/0 programming in the DECsystem10 is highly convenient for the user because all of the burdensome details of
programming are performed by the
operating system . The user informs the
operating system of his requirements
for I/O by means of UUO's contained in
his program. The actual input/output
routines needed are then called by the
UUO handler.
Since the operating system channels
communication between the user program and the device, the user does not
need to know all the peculiarities of
each device on the system. In fact, Ihe
user program can be written in a similar
manner for all devices. The operating
system will ignore, without returning an
error message, operations that are not
pertinent to the device being used.
Thus, a terminal and a disk file can be
processed identically by the user program. ln addilion. user programs can be
written to be independent of any particular device. The operating system
allows the user program to specify a
logical device name, which can be as·
sociated with any physical device at Ihe
time when the program is to be executed. Because of this feature, a program
that is coded to use a specific device
does not need to be rewritten if the
device is unavailable. The device can
be designated as a logical device name
and assigned to an available physical
device with one command to the operating system.
Data is transmitted between the device and the user program in one of two
methods: unbuffered mode or buffered
mode. With unbuffered data modes,
the user in his program supplies the
device with an address, which is the
beginning of a command list . Essentially, this command list containspointers
specifying areas in the user's allocated
core to or from which data is to be translerred. The user program then waits
until the operating system signals that
the entire command list has been processed. Therefore, during the data
transfer, the user program is idly waiting
for the transfer to be completed.

Data transfers in buffered mode utilize a ring of buffers set up in the user's
core area. Buffered transfers allow the
user program and the operating system's 110 routines to operate asyn chronously. As the user program uses
one buffer, the operating system processes another one by filling or emptying it as interrupts occur from the device. To prevent the user program and
the operating system from using the
same buffer at the same time, each
buffer has a use bit that designates who
is using the buffer. Buffered data transfers are more efficient than unbuffered
transfers because the user program
and the operating system can be working together in processing the data.
Several steps must be followed by
the user program in order for the operating system to have the information it
needs to control the data transfers.
Each step is indicated to the operating
system with one programmed operator. In the first step, the specific device
to be used in the data transfer must be
selected and linked to the user program with one of the software 110 channels available to the user's job (OPEN or
INIT programmed operators). This device remains associated with the software 110 channel until it is disassociated from it (via a programmed operator) or a second device is associated
with the same channel. In addition to
specifying the 1/0 channel and the device name, the user program can supply
an initial file status, which includes the

type of data transfer to be used with the
device (e.g., ASCII, binary), and the
location of the headers to be used in
buffered data transfers. The operating
system stores information in these
headers when the user program executes programmed operators, and the
user program obtains from these headers all the information needed to fill or
empty buffers.
Another set of programmed operators (IN BUF and OUTBUF) establishes
the actual buffers to be used for input
and output. This procedure is not necessary if the user is satisfied to accept the
two buffers automatically set up for him
by the operating system .
The next step is to select the file that
the user program will be using when
reading or writing data. This group of
operators (LOOKUP and ENTER) is not
required for devices that are not filestructured (e.g., card reader, magnetic
tape, paper-tape punch). However, if
used, they will be ignored, thus allowing
file-structured devices to be substituted for non-file-structured devices
without the user rewriting the program.
The third step is to perform the data
transmission between the user program and the file (IN, INPUT, OUT, and
OUTPUn. When the data has been
transmitted to either the user program
on input or the file on output. the file
must be closed (CLOSE, fourth step)
and the device released from the channel (RELEASE, fifth step). This same
sequence of programmed operators is
performed for all devices; therefore,
the 110 system is truly device-independent because the user program does
not have to be changed every time a
different device is used.
In addition to reading or writing data
to the standard 1(0 devices, provisions
are included in the operating system for
using the terminal for 1/ 0 during the
execution of the user program. This
capability is also obtained through programmed operators. As the user program is running, it can pause to accept
input from or to type output to the terminal. The operating system does all buffering for the user, thus saving programming time. This method of terminal If 0
provides the user with a convenient way
of interacting with a running program.
72

Command
Control Language
By allowing resources to be shared
among users, the timesharing environment utilizes processor time and system resources thatarewasted in singleuser systems. Users are not restricted
to a small set of system resources, but
instead are provided with the full variety
of facilities. By means of his terminal,
the user has on-line access to most o f
the system's features. This on-line access is available through the operating
system command control language,
which is the means by which the timesharing user communicates with the
operating system.
Through the command language, the
user controls the running of a task, o r
job, to achieve the desired results:
create, edit. and delete files ; start, suspend, and terminate a job; compile,
execute, and debug a program . In add ition, since GALAXY batch software
accepts the same command language
as the timesharing software, any user
can enter a program into the batch run
queue. Thus, any timesharing termina l
can act as a remote job entry terminal.
When the user types commands
and/or requests on his terminal, the
characters are stored in an input buffer
in the operating system, The command
decoder examines these characters in
the buffer, checks them for correct syntax. and invokes the system program or
user program as specified by the
command.

File System
Mass storage devices, such as disks
and drums, cannot be requested for a
user's exclusive use, but must be shared
among all users. (An exception is the
assignment of a disk structure to a single
user; I.e., a ·private ~ disk structure.)
Because many users share these devices, the operating system must ensure independence among the users :
one user's actions must not affect the
activities of another unless the users
desire to work together. To guarantee
such independence, the operating system provides a file system for disks,
disk packs. and drums. Each user'sdata
is organized into groups of 128-word
blocks called files. The user gives a
name to each of his files, and the list of
these names is kept by the operating
system for each user. The operating
system is then responsible for protecting each user's file storage from intrusion by unauthorized users.
In addition 10 allowing independent
file storage for users the operating system permits sharing of fites among individual users. For example, programmers working on the same project can
share the same data in order to com plete a project without duplication of
effort. The operating system lets the
user specify protection rig hIs, or codes,
for his files. These codes designate If
other users may read the file, and after
access, jf the files can be modified in
any way. A new facility called File
DAEMON allows the user to specifically
permit or deny access to any lile, or set
of fites, for specific users. The user may
also create a log of accessos to his files
for later review, proprietary program
billing, etc.

On each clock interrupt. control is
given to the command decoderto Interpret and process one command in the
Input buffer The command appearing
Ifl the input buffer is matched with the
table of valid commands accepted by
the operating system. A match occurs
rf the command typed in exactly matches
a command stored In the system, or if
the characters typed in match the beglnnmg characters of only one command (i e , constitute a unique abbreviaOOn). When the match IS successful,
the legality information (or flags) assoCiated With the command is checked to
see If the command can be performed
Immediately For instance, a command
must be delayed if the job is swapped
out to the disk and command requires
that the job be resident in core ; the
command IS executed on a later clock
ItIl errupt when the job is back in core.
It all cond Illons as specified by the legalIty flags are met, control is passed to the
appropriate program.

The user of the DECsystem -l0 is not
required to preallocate file storage : the
operating system allocates and deallocates the file storage space dynamically on demand. Not only is this convenient for the user because he does
not have to worry about allocation
when creating files, but this feature also
conserves storage by preventing targe
portions of storage from being unnecessarily tied up. However, a large
batch job which needs to preallocate
space may do so.
Files are assigned protection levels
for each of three classes of users : self:
users with a common project number;
and all users. Each user class may be
assigned a different access privilege;
there are eight levels in each of the three
user classes. The owner of a file may
always change its protection.
In addition the File DAEMON is called
on all access failures if the owner protection is 4,5.6.7 ... Note that the protection used by the system to determine
access right after a File DAEMON call is
provided by the file DAEMON.

Tab" VIII, File Protection Scheme,
Protection Level

Access Code

Access Privi leges

Greatest Protection

7
6
5

No access privileges
(except by owner)
EXECUTE ONLY
READ , EXECUTE
APPEND, READ. EXECUTE
UPDATE. APPEND , READ. EXECUTE
WRITE, UPDATE. APPEND . READ. EXECUTE
RENAME . WRITE. UPDATE, APPEND , READ, EXECUTE
CHANGE PROTECTION, RENAME, WRITE, UPDATE , APPEND.
READ, EXECUTE

Least Protection

FUeHandler
To reference'" file, the user does not
need to know where the file is physically
tocated. A named file is uniquely identified in the system by a file name and
extension, an ordered list of directory
names (UFDs and SFDs) which identify
the owner of the file, and a file structure
name which identifies the group of disk
units containing the file,
Usually a complete disk system is
composed of many disk units of the
same and/or different types. Therefore,
the disk system consists of one or more
file structures- a logical arrangement
of files on one or more disk units of the
same type. This method of file storage
allows the user to designate which disk
unit of the file structure he wishes to
use when storing files. Each file structure is logically complete and is the
smallest section of file memory that can
be removed from the system without
disturbing other units in other file structures. All pointers to areas in a file structure are by way of logical block numbers rather than physical disk addresses;
there are no pointers to areas in other
file structures, thereby allowing the file
structure to be removed.

File Structures
A file structure contains two types of
files; the data files that physically contain the stored data or programs, and
the directory files that contain pointers
to the data files. Included in these directory files are master file directories,
user file directories, and sub-file directories. Each file structure has one master
file directory (MFO). This directory file
is the master list of all the users of the
file structure. The entries contained in
the MFD are the names of all the user
file directories on the file structure.
Each user with access to the file structure has a user file directory (UFO) that
contains the names of all his files on that
file structure ; therefore, there are many
UFOs on each file structure. As an entry
in the user file directory, the user can
include another type of directory file, a
sub-file directory (SFO). The sub-file
directory is similar to the other types of
directory files in that it contains as entries the names of all files within that
sub-directory. This third level of directory allows groups of files belonging to
the same user to be separate from each
other. This is useful when organizing a
large number of files according to func tion. In addition, sub-file directories
allow non-conflicting, simultaneous
runs of the same program using the
same file names.
As long as the files are in different
sub-file directories, they are unique.
Sub-file directories exist as files pointed
to by the user file directory, and can be
nested to the depth specified by the installation at system generation time.
74

F1$e Protection
All disk files are composed of two
parts: data and information used to retrieve data. The retrieval part of the file
contains the pointers to the entire file,
and is stored in two distinct locations on
the device and accessed separately
from the data. System reliability is increased with this method because the
probability of destroying the retrieval
information is reduced; system performance is improved because the
number ofpositionings needed for random-access methods is reduced, The
storing of retrieval information is the
same for both sequential and randomaccess files. Thus a file can be created
sequentially and later read randomly,
or vice versa, without any data conversion.
One section of the retrieval information is used to specify the protection
associated with the fite. This protection
is necessary because disk storage is
shared among all users, each of whom
may desire to share files with, or prevent files from being written, read, or
deleted by other users. As discussed
above, these protection codes are
assigned by the user when the file is
created and designate the users who
have privileges to access the file,

DlskOuotas
Disk quotas are associated with each
user (each project-programmer number) on each file structure in order to
limit the amount of information that can
be stored in the UFO of a particular file
structure. When the user gains access
to the computing system, he automatically begins using his logged-in quota.
This quota is not a guaranteed amount
of space, and the user must compete
with other users for it. When the user
leaves the computing system, he must
be within his logged-out quota. This
quota IS the amount of disk storage
space that the user is allowed to maintain when he is not using the system and
IS enforced by the system program that
lS used in logging off the system. Ouotas are determined by the individual
Installation and are, therefore, used to
ratIOn disk resources in a predetermined manner.
To the user, a file structure Is like a
device; i.e., a file structure name or a set
of flle structure names can be used as
the device name in command strings or
UUO calls to the operating system. AI·
though file structures or the units compoSing the file structures can be specified by their actual names, most users
specify a general. or generiC, name
(DSK) whIch wfJI cause the operating
system to select the appropriate file
struc ture Theapproprlate file structure
IS determined by a jab search list. Each
JOb has ItS own Job search list with the
file structure names in the order in
whic h they are to be accessed when
the generic name is specilied as the
deVice. ThIS search list is established by
LOGIN and thus each user has a UFO
for hiS prOJect-programmer number in
each fIle structure In which LOGIN allow s him to have files.

File Opera!",ns
File writing on the disk can be defined
by one of four methods : creating. superseding, updating and simultaneous updating. The user is creating a file if no
other file of the same name exists in the
user's directory on the indicated file
structure. If another file with the same
name already exists in Ihe directory,
the user is superseding, or replacing,
the old file with the new lile. Other users
sharing the old file at the time it is being
superseded continue using the old file
and are not affected until they finish
using the file and then try to access it
again. At that time, they read the new
file. When auserupdales a file, he modi·
fies selection parts of the file without
creating an entirely new version. This
method eliminates the need to recopy
a file when making only a small number
of changes. If other users try to access
a ft1e while it is being updated, they receive an error indication issued by the
system.
Many users can update the same file
through the use of the simultaneous
update feature. This allows users to
work with the same data base simultaneously. An ENO/DEO facility is also
offered to allow record level lock out
and thus eliminate race conditions
where multiple users are attempting to
read andlor write the same record.
75

Disk Storage Management
File storage is dynamically allocated
by the file handler during program oper·
ations, so the user does nol need to give
initial estimates of file length or the
number of files. Files can be any length,
and each user may have as many files
as he wishes. as long as dIsk space IS
available and the user has nol exceeded
his logged-m quota. ThiS feature IS ex'
tremely useful during program devel·
opment or debuggmg when the final
size of the file is st.1I unknown. However,
for efficlenl random access, a user can
reserve a contiguous area on the disk if
he desires. When he has completed
processing, he can keep his preallo'
cated file space for future use or return
it so Ihat other users can have access 10
,I.

Memory
Management

Input/Output
Peripheral Device Assignment

With the command language, the
user can also request assignment of
any peripheral device (magnetic tape.
DECtape, and private disk pack) for exclusive use. When the request for assignment is received, the operating system verifies that the device is available
to this user, and the user is granted its
private use until he relinquishes it.ln this
way, the user can also have complete
control of devices such as card readers
and punches, paper tape readers and
punches, and line printers.
Spooling

When private assignment of a slowspeed device (card punch, line printer,
paper tape punch, and plotter) is not
required, the user can employ the spool-

ing feature of the operating system.
Spooling is a method by which output to
a slow-speed device is placed on a highspeed disk or drum. This technique prevents the user from consuming unnecessary system resources while waiting
for either a device to become available
or output to be completed. In addition,
the device is managed to a better degree because the users cannot tie it up
indefinitely, and the demand fluctuations experienced by these devices
are equalized.

The DECsystem-10 is a multiprogramming system; i.e., it allows multiple
independent user programs to reside
simultaneously in memory and to run
concurrently. This technique of sharing
memory and processor time enhances
the efficient operation of the system
by switching the processor from a program that is temporarily stopped because of 110 transmission to a program
that is executable. When core and the
processor are shared in this manner,
each user's program has a memory
area distinct from the area of other
users. Any attempt to read or change
information outside of the area a user
can access immediately stops the program and notifies the user.
Because available memory can contain only a limited number of programs
at anyone time, the computing system
employs a secondary memory, usually
disk or drum, to increase the number of
users serviced. User programs exist on
the secondary memory and move into
memory for execution. Programs in
memory exchange places with the programs being transferred from secondary memory for maximum useof avail·
able main memory. Because the transferring, or swapping takes place directly
between main memory and the secondary memory, the central processor
can be operating on a user program in
one part of memory while swapping is
taking place in another. This independent, overlapped operation greatly
improves system utilization by increasing the number of users that can be
accommodated at the same time.
76

To further increase the utilization of
memory, the operating system allows
users to share the same copy of a program or data segment. This prevents
the excessive memory usage that re sults when a program is duplicated for
several users. A program that can be
shared is called a reentrant program
and is divided into two parts or seg ments. One segment contains the code
that is not modified during execution
(e.g., compilers and assemblers) and
can be used by any number of users.
The other segment contains non-reentrant code and data. The operating
system provides proteclionlfor shared
segments 10 guarantee that they are
not accidentally modified.

Virtual Memory
The virtual memory option permits a
user program to execute with an address space greater than the physical
memory actually allocated to that program during execution. User jobs are
swapped as described a bove. However,
the enllre program may not necessarily
be in core during execution. Programs
are divided into pages each of which is
512'words long. Some of these pages
may remain on secondary storage while
the program executes. When a virtual
memory job attempts 10 access a page
that IS not in core, a page fault handler
decides which page or pagesto remove
from core and which to bring in from
secondary storage.
Unlike the virtual memory implementation on other systems. this DECsyslem-10 feature is an option. Each site
may determine ils own need for virtual
memory and install il at their convenlence The system administrator may
grant the privilege for uSing virtual
memory only to those users who truly
need lIs capabilities. Those users who
are granted the privilege of using virtual
memory may elect to invoke the feature
for only those programs that could not
execute without the virtuat memory
capability.
The virtual memory users may elect
to use the system page fault handler
or they may use a handler that is more
tailored to the particular application or
program behavior. Finally, it is important
to pomt out that only those users actually USing the virtual memory feature
are affected by any additional overhead associated with a demand paging
system. Non-virtual users execute as
they would in a non-virtual system with
no discernible difference in performance.

Multi-Processor
Systems
DECsystem-l0 Dual Processor systems are composed of two CPU·s. designated the primary processor (master) and the secondary processor (slave).
The primary processor is connected to
all of the memory in the system and has
allof the system'S peripheral 110 equipment connected to its 110 bus. The
secondary processor also has access
to all of memory, however. there are
normally no 110 devices on this processor's 110 bus. The primary processor
performs exactly the same operations
as the processor in a single processor
system. This includes all 110 operations.
swapping. core allocation. resource
allocation and command decoding. The
secondary processor also performs
scheduling and execution of user jobs
according to the same algorithm used
in a single processor system.
The secondary processor executes
user jobs and scans the same job queues
as the primary processor. However,
since the slave cannot doany standard
110. it looks for any compute bound
jobs which are in core and runnable. A
software interlock has been added to
the scheduler to prevent the possibility
of both processors trying to execute
the same job at the same time. Whenever a job being executed by the secondary processor req uests an I/O operation to be performed the jobis stopped
and marked for execution on the mas·
teronly. Thus both processors run com·
pletely asynchronously. both executing
the same scheduler, doing the same
job accounting and using the same job
queues.
77

The existence of dual processors
gives OECsystem-l0 users a large
scale computing capability, especially
in the areas of highly compute bound
jobs and non -interactive batch jobs.
The existence of a slave more or less
dedicated to user computation allows
these jobs to be carried on in the systems with little interference with time
sharing users. The performance goal is
to provide a system in which each customer can improve the service offered
to his users over a single processor
compute bound system. Either the customer can add more users with the same
response time or he can keep the same
number of users and reduce turn around
time for compute bound jobs.

Communications
Software

Inter-job
Communication
Shared Data Areas
The DECsystem-10 operating system

enables a user to communicate with
other jobs through the use of sharable
data areas. This also enables a data
analysis program, for example to read
or write an area in the real-time job's
core space. Since the real-time job associated with the data acquisition would
be locked in core, the data analysis pro-

gram residing on secondary memory
would become core resident only when
the real-time job had filled a core buffer with data. Operating system calls
can be used to allow the data analysis

program to remain dormant in secondary memory unlil a specified event
occurs in the real-time jOb: e.g., a buffer

has been filled with data for the data
analysis.

Inter-Process Communtcatlon
Facility
The Inter-Process Communication
Facility (IPCF) provides the capability
for independent jobs to communicate
with one another. For example, if several programs are involved in processing or maintaining a data base, it is possible that one program might want to inform the others of any modifications it
made to the data. A job using IPCF cannot make any changes to another job so
protection is in no way sacrificed when
using the IPCF feature.
In order to use the IPCF, each participating job that wishes to receive communication from other jobs must request a unique process identifier (PID)
from the system. The transmitting job
then may send a ~ packet .. of information to another job. (In addition to the
information, the system automatically
provides a ~ return address· so that the
receiving program can respond to the
sender.) The monitor maintains a linear
queue (the Mmailbox~) for each job using IPCF. The packet (or packets) will be
kept in the mailbox until the receiving
job retrieves it. This queue is not created untit a job sends an IPCF packet
and it does not occupy any space until
such time. The maximum number of
packets allowed in a queue at anyone
time is determined by a -receive" quota
that may be set at each installation for
each user. (If no quota is set by the installation, the standard default is five.)
On systems with the virtual memory
option, the packet could be an entire
page. In this case, the monitor takes
advantage of the page mapping hardware of the KltO and K110 to transmit
the page without actually copying it.
78

DECsystem-l0 users have a wide
selection of communications products
to enhance or facilitate their computing needs. Within the multi -task environment of TOPS-IO. functionality
exists for:
• Asynchronous communication-the
typical vehicle for interactive timesharing or transaction-oriented terminals
• Synchronous
communicationsfor connection of remote batch, remote terminal concentration and
computer-to-computer links.
The important featUre of DECsystem-l0 communications software is its
implementation as an integral part of
the TOPS-tO Operating System. The
monitor, not the user, handles the communications housekeeping, and all
communications products are fully
supported within the TOPS-l0 environment. Appropriate synchronous line
protocols -D IGITAL's own DDCMP or
BISYNC-are supported.
Users may configure networks with
simple or complex topologies utilizing
the DNB7 family of Universal Front End
equipment. The DAS-80 and OAS-go.
series remote stations/concentrators
can then be used to expand the network
topologies. In addition, DECNET-l0
permits the DECsystem-1O to utilize
task-to-task communication with other
DECsystem-tO's or with any other DEC supplied computer system which supports DECNET. The DAS-61 and DAS-62
can be used to do IBM 2780, 3780 or
HASP multi-leaving emulation and termination.
Additional detaits concerning the
DECsystem-l0 communications capability and products are included in the
Data Communications Section.

GALAXY·10
Batch

Timesharing

The OECsystem-l0 is designed lor
the concurrent operation of Ilmesharng. muillstream batch, real-time, and
remot e communications 10 either SingleOt dual-processor systems In providIng these multifunction capabilities. the
DECsystem -lO services Interactive
lIsers, operates local and remote batch
stations. and performs data acquisition
and control functions lor on -line laboratories and other real-lime projects. By
dynamically adjusting system operation, the OECsyslem -l0 provides many
fea tures for each class 01 user and is
therefore able to meel a wide variety of
computational reqUirements.

Timesharing lakes maximum advantage of the capabilities of the computing
system by allowing many independent
users to share the facilities of the DEC system-10 simultaneously. Because of
the interactive. conversational. rapld response nature of TOPS-lO time-sharing. a wide range of tasks-from solving
simple mathematical problems to implementing complete and complex
information gathering and processing
networks-can be performed by many
users concurrenlly. The number of
users on the system at anyone time
depends on the system configuration
and the job mix on the system. DEC system-10 timesharing is designed to
support in excess of 200 active users.
Interactive terminals can include CATs.
hard copy terminals and other devices
which operate at speeds of 110 to 9600
baud. Terminal users can be located at
the computer center or at remote locations connected to the computer center by communication lines.
Timesharing on the DECsystem-lO is
general purpose; i.e .. the system is designed in such a way that the command
language, inpul/output processing. file
structures, and job scheduling are
independent of the programming language being used. In addition. standard
software interfaces make it easy for the
user to develop his own special language or systems. This general purpose approach is demonstrated by the
many special'purpose programming
languages implemented by DECsystem-l O users.
79

GALAXY·l0 batch software enables
the DECsystem-l0 to execute in excess
of 30 batch jobs concurrently with timesharing jobs. Just as the timesharing
user communicates with the system by
way of his terminal, the batch user normally communicates by way of the card
reader. (However, he can also enter his
job from an interactive terminal.) Unlike
the timesharing user, the batch user
can punch his job on cards, insert a few
appropriate control cards, and leave
the job for an operator to run. In addition, the user can debug the program in
the time sharing environment and then
run it in batch mode without any additional coding.
The GALAXY -10 system consists of a
series of programs: QUASAR. the system queue manager and scheduler,
SPRINT, the input spooler. BATCON. the
batch controlier, and the output spoolers. LPTSPL and SPROUT. The input
spooler is responsible for reading the
input from the input device and for entering the job into the batch controller's
input queue. The input spooler sends a
message to aUASAR to do the actual
entering mto the batch input queue.
Although the input spooler is oriented
toward card reader input, disk and magnellc tape also can be handled. The input information is then separated according to the control commands in the
input deck and placed into disk 'iles for
subsequent processing. In addition, the
input spooler creates the job's log file
and enters a report of its processing of
the job, along with a record of any operator intervention during its processing.
The log file is part of the standard output
that the user receives when his job
terminates.

Afterthe inputspooler reads the endof-file and closes the disk files, it makes
an entry in the batch controller's input
queue. The batch controller processes
batch jobs by reading the entries in its
queue. The control file created by the
input spooler is read by the batch controller, and data and user program commands are passed directly to the user's
job. Operating system commands are
detected by the batch controller and
passed to the operating system for action. Most operating system and user
program commands available to the
timesharing user are also available to
the batch user, Therefore, only one
control language need be learned for
both timesharing and batch. During the
processing of the job and the control
file, the batch controller adds information to the log file for later analysis by
the user.
QUASAR is responsible for scheduling
jobs and maintaining both the batch
controller's input queue and the output
spooling queues. A job is scheduled to
run under the batch controller according to external priorities, processing
time limits, and core requirements
which are dynamically computed according to parameters specified by the
user for his job, such as start and deadline time limits for program execution.
QUASAR makes an entry for the job in
the batch input queue based upon the
various priorities. After the job is completed an entry is made in the output
queues forthe job'sspooled output and
the job's LOG file.
The output spooling programs improve system throughput by allowing
the output from a job to be written temporarily on the disk for later transfer
instead of being written immediately
on a particular output device. The log
file and all job output are placed into
one or more output queues to await
processing. When the specified device
is available, the output is then processed by the appropriate spooling
program. These spooling programs
may be utilized by all users of the computing system.

Use of System Features
The GAlAXY-1O batch software employs many of the computing system's
features in order to operate with maximum efficiency. Because core memory is not partitioned between balch
and timesharing jobs, batch jobs can
occupy any available area of core. Fast
throughpullor high-priority batch jobs
is accomplished with the same swapping technique used for rapid response
to interactive users. When available
core is not large enough for a highpriority batch job, the operating system
transfers programs of lower priority to
secondary memory in order to provide
space for the job. This transfer is done
at the same time that the processor is
operating on another job. Thus, processing can be overlapped with swapping (and other I/O) to utilize time that
would otherwise be wasted, Batch jobs
can also share prog rams with timesharing and other batch jobs. Only one copy
of a sharable program need be in core to
service any number of batch and timesharing jobs at the same time.

Flexibility
GALAXY-lO batch allows the user
great flexibility. The inpul spooler no(mally reads from the card reader, but
can read from magnetic tape or disk
in order 10 create a control file on disk
and to enter the job into the batch controller's input queue. However, a job
can be entered from an interactive terminal, in which case the user bypasses
the input spooler and creates a control
file on disk for the batch controller. The
control file contains the operating system commands and user program commands necessary to run the job. The
user then enters the job into the batch
controller's input queue by way of an
operating system command string. In
the command string, the user can include switches to define the operation
and set the priorities and limits on core
memory and processor time.

'''''''!~'

1'0 _
/

1M".

00' ... _ . . .

'....:..o.IIl.

-L-C

' !...c"-I-l
'---'.-~, .."':- t
I'STU.

01', ....'0.

Real-time

Job Dependency
Although jobs are entered sequen llally in to the batch system, they are not
necessarily run in the order that they
are read because of priorities either set
by the user in an input spooler control
command or computed by the queue
manager when determining the scheduling of jobs, Occasionally, the user
may wish to submit jobs that must be
executed In a particular order: in other
words, the execution of one job is dependent on another. To ensure that jobs
are execu ted in the proper order, the
user must specify an initial dependency
count In a control command of the dependent Job This dependency count is
then part of the Input queue entry, A
control command in the job on which
the dependent Job depends decrements the count. When the count becomes zero, the dependent job is
executed
Error Recovery
The user can control system response
to error conditions by including commands to the batch controller which will
aid In error recovery, These commands
are copied Into the control file by the
Input spooler With error recovery
commands, the user specifies the action
10 be taken when hiS program contains
a fatal error, as for example, to skip to
the next program or to transfer to a
special user-written error handling
routine. If an error occurs and the user
did not mclude error recovery condilions In hiS Job, the batch controller Inltiales a standard dump of the user's core
area and terminates the job. This core
dump provides Ihe user with the means
to debug his program,
AlthOugh the batch system allows a
large number of parameters to be specIfied, It IS capable of operating wllh
very few user-specified values. If a
parameter is missing, the batch system
supplies a reasonable default value.
These defaults can be modified by the
IndiVidual Installations.

Computing

Operator Intervention
Normal operating functions performed by the programs in the batch
system require little or no operator
intervention; however, the operator
can exercise a great deal of control if
necessary. He can specify the number
of system resources to be dedicated to
batch processing by limiting the number of programs and both the core and
processor time for individual programs.
He can stop a job at any point. requeue
it, and then change its priorities. By examining the system queues, he can determine the status of all batch jobs. In
addition, the programs in the batch
system can communicate information
to the operator and record a disk log of
all messages printed at the operator's
console, All operator intervention during the running of the input spooler and
the batch controller causes messages
to be written in the user's log file, as well
as in the operator's log file, for later
analysis.
81

For a system to be satisfactory for
real-time operations, two important requirements must be met. The more
important requirement is fast response
time. Because real-time devices may
not be able to store their information
until the computing system is ready to
accept it. the system would be useless
for real-time if the response require ments of a real-time project could not
be satisfied. The operating system allocates system resources dynamically in
order to satisfy the response and computational requirements of real-time
jobs.
The second requirement is protection, Each user of the computing system must be protected from other users,just as the system itself is protected
from all user program errors. In addition, since real-time systems have
special real-time devices associated
with jobs, the computing system must
be protected from hardware faults that
could cause system breakdown. And,
because protection is part of the func tion of the operating system, the real time software employs this fealure to
protect users as well as itself againsl
hardware and software failures. Inherent in the operating system is the capability of real-time, and it is byway of calls
to the operating system that the user
obtains real -time services. The services
obtained by calls Within the user's program include:
• Locking ajob in core,
• Connecting a real -time device to the
priority interrupt system.
• PlaCing a job in a high-priority run
queue.
• Initiating the execution of FORTRAN
or machine language code on receipt of an interrupt.
• Disconnecting a real -lime device
from the priority interrupt system.

locking Jobs
Memory space is occupied by the
resident operating system and by a mix
of real-time and non-real-time jobs. The
only fixed partition is between the resident operating system and the remain derot memory so as not to lose information when its associated real -time
device interrupts (since there may not
be sufficient time to swap-in the job) the
job can request that it be locked into
core. This means that the job is not to be
swapped to secondary memory and
guarantees that the job is readily available when needed. Because memory is
not divided into fixed partitions, it can
be utilized to a better degree by dynamically allocating more space to realtime jobs when real-time demands are
high. As real-time demands lessen,
more memory can be made available
to regular timesharing and batch usage.

Real-time Devices
The real-time user can connect realtime devices to the priority interrupt
system, respond to these devices at
interrupt level, remove the devices
from the interrupt system, and/or
change the priority interrupt level on
which these devices are assigned.
There is no requirement that these devices be connected at system generation time. The user specifies both the
names at the devices generating the
interrupts and the priority levels on
which the devices function. The operating system then links the devices to
the operating system.
The user can control the real-time
device in one of two ways : single mode
or block mode. In single mode, the
user's interrupt program is run every
time the real-time device interrupts. In
block mode, the user"s interrupt program is run after an entire block of data
has been read from the real-time device. When the interrupt occurs from
the device in single mode or at the end
of a block of data in block mode, the
operating system saves the current
state of the machine and jumps to the
user's interrupt routine. The user services his device and then returns control
to the operating system to restore the
previous state of the machine and to
dismiss the interrupt. Any number of
real-time devices may be placed on any
available priority interrupt channel for
the program to read. When the specified
event occurs, the dormant program is
then activated to process the data. The
core space for the real -time job's buffer
area or the space for the dormant job
does not need to be reserved at system
generation time. The hardware working
in conjunction with the operating system's core management facilities provides optimum core usage.
82

High-Priority Run Queues
The real-time user can receive faster
response by placing jobs in high-priority run queues. These queues are examined before all other run Queues in
the computing system, and any runnable job in a high-priority Queue is
executed before jobs in other queues
In addition, jobs in high-priority queues
are not swapped to secondary memory
until all other queues have been scanned.
When Jobs in a high-priority queue are
to be swapped, the lowest priority job is
swapped first and the highest priOrity
job last The highest priority job swapped
to secondary memory is the first job to
be brought into core for immediate
execution. Therefore, in addition to
being scanned before all other Queues
for job execution, the high-priOrity
Queues are examined after all other
Queues for swapping to secondary
memory and before all other Queues
for swapping from secondary memory.

"High Availability"
TOPS·1O provides a number of fea tures which allow the syslem 10 conMue operating although some devices
may be Inoperable.
I) When errors occur on disks, tapes,
memory, or the slave CPU, TOPS-l0
will record the error dala and notify
the operator. If the error can be fixed
(e.g., put a disk back on-line), the
user may continue running without
further delay. Alternatively, the
operator may instruct the system to
remove (detach) the device, in
which case the jobs in error will be
notified and the system will continue
operation without the specified device. llthe error is in a bank of memory, TOPS-lO will even attempt to
move its own code (if any) out of the
failing memory. In the case of disks,
the system will attempt to migrate
any swapping space to another unit
to prevent loss of jobs.
2) RP04, and RP06 type disks may be
dual ported so that in case 01 controller failure, the packs may be
accessed via an alternate path. In
case of a unit failure, the pack may
be moved to a working unit.
3) With use of appropriate 110 bus,
memory bus, and device control
sWitches, DECsystem-lO's may be
configu red to provide redundancy
of hardware. Such systems may
allow any p iece of hardware to be
taken off-line and repaired while the
system continues operation (in
some cases, it may be necessary to
reload the system after a significant
reconfiguration).

Maintenance Features
The Diagnostic Strategy has produced a high quality of maintenance
aids which enforce the inc reased performance and availability of a DECsystem-tO. The design of the KLtO processor uses integrated diagnostic logic to
enable maximum visibility and reduce
Mhard-core ~ requ irements. Special software techniques are employed to maximize test coverage per diagnostic load,
thereby decreasing the mean time to
diagnose.
Board Level Diagnosis
The Writable Control Store feature of
the KL10 has enabled the MMicro Oiagnostic ~ alternate path methodology of
testing. This technology has enabled
generation of diagnostics which narrow
mallunctions to the board level with a
degree of confidence which exceeds
industry standards.
Maintainability was attacked from a
total system's concept, lor not only are
the CPU diagnostics capable of supporting the "Module Swap" philosophy
of repair. the new generation of peri pheral diagnostics gives the maintainer
the same qualities. The programs utilize
special diagnostic wrap around logic to
isolate suspected malfunctions to subsystem level. Then. through comprehensive logic analysis, not just functionality, the repair person is directed to the
failing module.

On· line Diagnosis
To further increase system availability, special features have been Incorporated into the monitor to enable
on -line preventive maintenance.
Emphasis has also been placed on
testing the thoroughness of delectability and the correctness of isolation.
Semiautomatic physical fault insertion
is qualifying and providing maturity enhancements for this product.
KUNIK Remote Diagnosis
One finalleature of the Maintenance
and Diagnostic Philosophy is the support of remote diagnosis (KlINIK). This
can provide distant maintenance personnel with hardware performance
statistics to improve the efficiency of
service on KL10 Based Systems.

Over the past few years, Datamation
Magazine has run an annual survey of
computer users, asking their opinions
on the quality of service they receive
from their vendors. One major area of
concern is post-installation maintenance
services. DIGITAL has continually ranked
first In quality and availability of service.
Major factors in this capability are the
number and placement of service personnel ; parts inventories available to
support local efforts; an organizational
structure that provides increasing expertise at each level; a management
reporting system that continuously
monitors all areas of service;and a wide
range of service agreements to meet
every customer need.

People
DIGITAL's hardware maintenance
organization includes 3000 hardware
speclahsts supported by an administrative staff of over 1000. Thesespecialists
are located in more than 3OOworldwide
offices for the greatest decentralization
of service availability.
Large Systems service engineers typically enter DIGITAL with more than four
years of field experience. They then
undergo four months of intensive trainIng at DIGITAL, followed by yearly updates In new products and technology.
They work with product support teams
who assure smooth transitions of new
products -from development to testing
to Installation-and provide consultation
and aSSistance for all service locations.

Parts
The size and location of DIGITAL's
parts inventories-at local, district. regional, and headquarters operationsare computer-optimized by our own
DECsystem-l0, which takes into account
the needs of both existing and new installations. The DECsystem-l0, in concert with PDP-l1 computers at regional
offices, assures that parts resources
are available locally to solve more than
90% of user problems.
For those problems requiring parts
not available immediately, DIGITAL has
a priority parts system utilizing inventories at district, regional and corporate
levels. All priority parts are shipped by
specialized air-freight carriers.
87

Support
Field Service's hierarchical organization places the greatest concentration
of resources at the local level, with supporting facilities at each ascending level
in the group. Continuous monitoring of
service activity at all levels of Field Service management focuses attention on
our worldwide systems base so that
resources can be mobilized as required.

Education is an integral part of the
total Digital customer service system .
We believe in training, not only for ourselves, but also for our customers ..Your
employees wilt, through education, extract greater performance from your
computer.
To provide this training, we have established completely equipped training
centers in a dozen locations around the
world. Our staff at these centers consists of fuU -time instructors dedicated
to computer training .
The education DIGITAL offers includes
standard and custom courses in both
hardware and software. Our current
schedule includes over 90 standard
courses, ranging in duration from one
to five weeks.
DIGITAL recognizes that you may
have a unique requirement that can
best be met with education at your location. Our on-site program meets this
need by designing and conducting
courses where and when you choose.

To give flexibility to this structure and
provide services that meet users exact
needs, DIGITAL offers a variety of service agreements. These agreements
range from coverage 12 hours/day, five
days/week to around-the-clock maintenance coverage. Occasional service,
on a time and materials basis, is available to users who elect to perform selfmaintenance, as weU as off-site repair of
electro-mechanical assemblies through
16 Product Repair Centers in the U.S.
and in Europe.
88

Good service demands outstanding
logistics. Spares availability minimizes
computer repair time. Our materials
inventory network recognizes this concept- and strengthens the total DIGITAL support system.
The first level of spares is often at
your own computer site. From this point
the inventory is in echelons at the
Branch, District, Regional, and Headquarters locations. Our own DECsystern-tO keeps track of this support system, providing replacement parts when
needed .
For OIGITAL computers located in
areas on the fringes of our service
capabilities. and for customers who use
our maintenance on an "as available~
basis, DIGITAL supplies spares planning and inventory procurement assistance.

DIGITAL is a major publisher of manuals, handbooks, and engineering literature. These documents support
more than 65,000 installed DIGITAL
computers. They meet user requirements for installation, maintenance,
education and operation . They provide
an authoritative guide to DIGITAL systems.
89

One example is DEC-D-LOG. Maintaining current systems and documents
is a critical task. DEC-D-lOG satisfies
this requirement by listing and explaining engineering improvements as they
evolve. This information is available to
keep you abreast of the latest technological developments.

The DIGITAL software organization
represents over 3,000 man-years of experience gained from the development
and support of operating systems used
in more than 65,000 computer installations. DIG ITAL 's software varies in compexity from real-time executives for
minicomputers tothe TOPS-10Monitor
of the DECsystem-10. Applications
cover the spectrum from process control and monitoring scientific experiments to implementing reservation and
inventory control systems.
DIGITAL offers a wide range of software services. These services range
from the personal attention of a skilled
software consultant to the dislribution
of up-to-date sohware and software information. In this way you can get the
most out of your DECsystem-10 and
keep pace with advancements in software.

You purchase only what you need.
Software components, including manuals and updates, can be purchased as
part of a Software Maintenance Service
or ordered separately from the Software Distribution Center. Software
maintenance plans for the DECsystem10 include:
1. Software Notebook Updates-Each
customer receives two sets of comprehensive software notebooks
which can be kept current via periodic update packages. You are assured of always having the most current documentation published.
2. Program Updates-Subscribers receive the latest software versions
along with all available Mbug-fixes"
on magtape.
3. Software DISPATCH-This service
provides all available code corrections as well as a copy of all customer-generated Software Performance Reports published as an
early warning service. This is a comprehensive publication aimed at the
customer in a dynamic, growing
software environment.
90

4 . Expedited Software Performance
Report Service-This service provides a very fast priority response
system with personalized replies
returned directly to the originator,
thus bypassing normal lags associated with publication and program
update cycles. This insures that any
problems you encounter will be
corrected.
5. Consulting Service- These are available on a short-term, per-call basis
or for a longer term scheduled or
resident period. Consultants can install software updates, train new
employees, and recommend procedures that result in top performance by your software system.

The Advanced Systems Group, an
integral part ofthe DECsystem -10 product group, meets special customer's
needs by augmenting the standard
products and services of the DECsystem -l0. The Advanced Systems Group
extends the range of the DECsyslem-l 0
product and services by providing:
1. Hardware/Software Design and
Development- Engineering for special products and modifications to
standard products, with emphasis
in Ihe areas of communications, nelwork systems, high availability and
redundant systems, and special
configurations.

2. Systems Project Management for
large and complex configurations
including such functions as systems
evaluation and design, systems
planning for future expansion, extended factory systems testing, special installation backup and support,
and extensions to the OECsystem 10 acceptance test procedures.
3. Repeat Manufacture of previously
designed and developed special
products.
Advanced Systems Group products
maintain DIGITAL's high standard of
quality. All hardware products are supportable under DECsystem-l 0 field
service support plans and are supplied
with full documentation, prints and diagnostics.
91

Support of special software is provided through a centralized support
group on an individual basis for both
installation and Software Performance
Reports (SPR's).
Because of the customized nature
of these products, the Advanced Systems Group provides individual system
configu ration review, system integration and system installation assistances
when needed.

CORPORATION
Martborough, Massachusetts 01752

InIerMlionII, CIIiIiVa

a, Switzerland

TECHNICAL SUMMARY

DECSYSTEM

The Information In th is document Is subject to change wlthout notice and
should not be construed as a 'COmmitment by Digital Equipment Corporation,
Digital Equipment Corporation assumes no responsibility lor any errors that
may appear In this document.
Digital Equipment Corporation makea no representation that the Interconnection 0' Its products In the manner described herein wlll not In'rlnge on existing
or future petent rights, nor do the descriptions contained herein Imply the
granting of license to make, use, or sell equipment constructed in accordance
wlth Its description,
The software described In this document Is furnished under license and mey be
used or copied only In accordance with tha terms of such license,
Unless otherwise noted, K _ 1,024: M _ K',
DEC, DECUS, the Digital logo, PDP, VAX, DECnet, DECwriter, DECsystem,
DECSYSTEM, DIBOL, RSTS, RSX, UNIBUS, MASS BUS, and VT are trademarks 01 DIgital Equipment Corporation,
CopyrlghfO 1981 Digital Equipment Corporation, All rights reserved,

1/11-16

Contents
1 PREFACE
2 OVERVIEW
COMPONENTS ••••.•..•....•..••.•...••... '" .... .... 2-1
Processors ...••..... ".. •••..•.. ... ••••... . .
. .... 2-1
TOPS-20 Operating System ..... ... ............. ....... 2·'
RELIABILITY
................... .. ....
. ..... 2· 3
Software Design ....................... . •... .......... 2-3

System Availability ....... ............. ......

. .. .. 2-3

System Recovery ..
. . ... . . . . . • • .
. ..•. 2· 3
Error Reponing ...................
. ............ 2-3

3 THE USERS

FRONT·END SUBSYSTEM ....
. ................. 5·7
INPUT I OUTPUT SUBSYSTEM •......•.
. ... 5-8
Multiplexed I/O Bus
............ , , ..... 5·6
MASSBUS
........• ,.................
. ...... . . 5-9
UNIBUS •............••..•...•............. . ...

THE APPUCATION PROGRAMMER
The Programming Languages. . . .

........ 3-1
. . ............ 3·'

Application Tools

........•••......•••.••.• 3-'

THE SYSTEM PROGRAMMER

.•••.•.... • ....

. ...... 3·'

THESVSTEM MANAGER ............ .. ....... ..... " •.• 3-2
User Authoriza tion .••.••......•......••• . .... . .. .. .... 3-2
Privileges •.•••..••..••.•.......••••.... • ....•...•.... 3-2
AllocaUng Disk Storage Quotas .........
. ... 3-2
Controlling Resources ••..••..••.•.•.•. • .••••••••..••• 3-2
Schecluler Controls .........•..•............... ..... ... 3-2
Resource Accounting Statistics •..••.•••..• • ••....••... 3-3
Performance Analysis Statistics .......... . ••••....... .. 3-3
THE SYSTEM OPERATOR ............
. ....... 3-3
Operator Intarface ..•.•..••.•.•......•••.••••.•••.•..• 3-3
Controlling Batch Streams ••..•.•.....•••••••....••... 3-3
System Recovery
.................... 3-3
System Backup •••..•..•.......••......•• • ••...•••••• 3·3
USER UTILITIES ...........

....•.....

. ... 3-3

4 THE OPERATING SYSTEM
THE COMMAND LANGUAGE PROCESSOR
THE BATCH SYSTEM

... 4-1
....... . .4-1

JOBS AND PROCESSES .•..••.......••.....•.•.. .• ... 4·2
PROCESS COMMUNICA nON ...••••••........ • ...••... 4·2
DIrect Process Control .....•..•......... , .•••.•...• , .. 4-2
Interprocess Communication Facility. . . .
. ....... 4-2
SoHware Interrupt System ........................... .4·2
Enqueue / Dequeue (ENQIDEQ) ..........•.. .. ....... 4-3
Memory Sharing..... ..•..••..•........•...•.
. .4·3
THE TOPS·20 MONITOR .............................. 4·3
VIRTUAL MEMORY

MEMORY SUBSYSTEM ...... . .. ......... ......... .. . 5-5
Internal Memory ...•..••.••••.•• . •••.... ......... .... . 5·5
MOS Memory ........•. . .••• .••..................•• .. 5·5
Cache Memory ...•....
. ......•••••...••... 5-5
Organization .........••...••.•..••••••. .....••...... 5-6
System Control of Cache ........ .
. ............. 5·7
Memory Mapping on the Kl 100E .....
. . .....• 5-7

•...

. .. 4-4

VIRTUAL MEMORY OPERATIONS ••••..
.. .. 4-4
THE FilE SySTEM.................
. ............ 4-5
. . .4-5
Flies ................... ......... ...... . .......
File Protection ••.•••.•••••.....••••.•....•••.•.••.... .4·5
Fite Directories ...................................... 4-6
Groups ..............•..•..•.•••••••.................4-6
File Usage ••... • •..••.••.••••••.••••••...•...••••.•.•• 4·6
Archiving Files ...........................•..•.•.......4-6
Tape labelling .. • •..••.•..•••••.•.•••••..•..•••...•.•. 4-6
CONSOLE FRONT-END PROCESSOR AND SOFTWARE •• 4-6
Console Functions •..•••••••...•.................... .. 4-6
Command Tarmlnal Functions .••....••••..•...••..•••• .4·6
Peripheral Interface .....•.•..•...
. .•••.•...•. 4-6
Diagnostic/Maintenance Functions ......••..•......... 4-6

5 KL10-E PROCESSOR
EXECUTION BOX (EBOX) . . ••••. . . . . . . ..•• . ••• •.
. .. 5-1
Instruction Set ••..••.•.•••.....•.......••.••.. ..... ... 5-2
Meters
.........•...•.
. .5-4
Priority Interrupt System .................... . . ... . . ... 5·4

. ... 5·9

6 KS10 PROCESSOR
SYSTEM ARCHITECTURE ... ...•..•
, ..•. 6-1
KS I OTechnology .................
. .. .. 6-1
The KSIO Central Processing Unit ........... .... ...... . 6·1
. .. 6-2
Cache Memory •......•..•••..•.........•... .
Generat Reg isters ••...
. .....................•. 6-2
Mlcrostore ..•••••....••.•••.••.•..••.........•.... . . 6-2
Instruction Set •...•.•.....•......•.... .. ..........•... 6-2
Processor Modes •••••..•....•.•..••••••........ . .... 6-3
MEMORy ................ •••.... ....... .......
. .. 6-3
Memory Address Mapping ........................•... 6-3
MOS Memory ......••.••.....•• • •••....••• , •••..••... 6-4
MS10 memory •••...•..••..•.•.•.•••....•....••..•.... 6-4
CONSOLE SUBSYSTEM .............................. 6-4

7 THE PERIPHERALS
MASS STORAGE PERIPHERALS
.............•• 7·1
DiSks ................................................ 7·1
Tape Devices ..................•..••••••......••..... 7-1
UNIT RECORD PERIPHERALS .•..••.................• 7-2
lP20·A and ·B l ineprinter. ................•.
. .... 7·2
lP20·C end -0 Llneprlnters .............. , ............. 7-3
lP200 Llneprlnters .............................
. ... 7-3
Cardreaders .................... ..........
..7·4
PC 20 Paper Tape Reader / Punch ...................... 7-4
TERMINALS AND INTERFACES , ......... , ...... ... .... 7-4
lA 120 Hardcopy Terminal ••.
. .....•• 7·4
lA3S Hardcopy Terminal •..• , ..•.• , ................... 7·5
VT100 Video Terminal ........
........... ....... 7·5
DZlt Terminal Line Interlace .••.•..••• ,....
. .. 7-6
DH11 Programmable Asynchronous
Serial Line Multipl exer ..................
. ... 7·6
Dl 11 Serial line Asynchronous Interfaces
.... 7·6
DUP II Single Synchronous line Interface ...... ... •..•• 7·6
KMC11-A AU)tltlary Processor ......................... 7-S
DN20 COMMUNICAliONS FRONT END ...•.•.•..••.••. 7-6

8 THE LANGUAGES
TOPS-20 ASSEMBLER ................................ S-1
DEBUGGING TOOLS . . . • . . • . . . • . •• ....... . ..... .
. .. 8-1
FORTRAN .
...•...••..•.•.•......
. ..•. S·,
language extensions ... . .• . ... . ..... .
. ......... 8·2
Opti mization .•...........•...•. • • .••.....••....•••.••. 8·2
Debugging Tools •••.•..••..••..•••..•.•••.....••..•... 8-2
COBOL •.•.........••••.•...••.•.•••....••.....••.••. S-2
Data Types ..•••••..••••..••..•..•.......
. .• 8-3
StrIng Manipulation
. . . . . . . . . . . . . . .... .
. .. 8·3
Interactive COBOL execution ••.•.•...
. .... S-3
File Organization . ..... . . •. . ... . . . .. . ..... . .
. .. 8· 3
Library FaCility. ,
..................... ,
.•• S-3
ENTER Facility ....•••• , . •• . . . • . • . . .
. .. 8·3

Online Debugger .••....•.•.•...•.••.•...••••...
Source Program Input ••.•.•..•••••....•••••..
RERUN ...•.•...•.•••..••••••..•••••..•
COBOl·58 and COBOl·7.. ................. ..
AlGOl·20
•.••••...•••..••.•...•••.
Block Structure ..
.. .. . ... .. .• • ...
Procedures
• .... .. .... .. ...
CompIler and System Futures •• •... . •..••
OWN VarIables
.. • ...... ..
Switches .
. ........ ..
StrIng Constants
.....••..•
ObJect-TIme System
• ••• • •...••
BASIC·PlUS·2
•••.••••..
Fjle Capablhty
VIrtual Memory Arrays
Record Input/Output .
Data FOfmats and OperatIon. ..
Matrix ManlpulatJon •.•.
... . .. . .. . ... ••
ConditIonal Stalements and Program Segmentation
Debugging Tools
............. .
APl •.. .. .. •• ..
• •...•..
Data Structures
. • . .. . ... . • . .. .. •
Interacting with APl
•
System Commands. FunctIon • • and Variables .
Slatements
APl Statement &:ecutlon
Debugging Tools
Workspaces
File Organization
Error Analysis and Recovety
Convllfslon Package
8l1SS·36
Compiling
Debugging
File Organization
Compallbillty WIth Othllf languages

CPl
Immediate Mode
ProgramCreauon ••.
Debugging

. 8-3
8-3
8-<

'-'

8-5
8-5
8-5

8-5
8-5
8-8
8-8

'-6

8-6

'--77
'8-7
8-7

8-8
6-8
6-8
8-8

...
..8-',
..8-',

Data Manipulation Process
DBMS Modules
DBMS Utlhllu

10l
Intllfactsve Mode
DeI8fred MOde
IOl Statements
DBMS Files
Report Fonnatllng
SORT/ MERGE
TRAFFIC· 20

8·10
8·10
8·10

.8·tO

9 DATA MANAGEMENT
AND APPLICATION PRODUCTS
DBMS
.......... . ..... 9.'
COOASYl Compliance .. . • .. ....
. ............. 9.,
Data DescrlpUon Process . . • . . . . . . . .• . .. . .... . •.....•. 9.1

9-,

• .• 1-2
~

.........
...

... ..........

COGO· 20
PCS· 20

10 COMMUNICATIONS
OECNET· 20
......... .
DIGITAL Network ArchItecture .......•••••.
OECnat Functions
....•••..
DECnet· 20 Capabilities .
.. ................ ..
REMOTE JOB ENTRY STATIONS ..

,0-,
,0-,
'0-,
'0-,

INTERNET PROTOCOL EMULATORS •.....

'0-3
,0-3

OX/ TOPS· 20 DOCUMENT TRANSMISSION

'0-5

11 SUPPORT SERVICES
INSTALLATION

8·,

0-,

SOFTWARE SERVICES
Software Warranty
Software PrOduct ServICes
Professional Services

8·tO

9-,

............

8-'

8-,

~,
~,

.............

8-,

8·'

.............

EOUCA nONAl SERVICES
Course OptIOnS
TOPS·20 Courses
HARDWARE SERVICES
COMPUTER SPECIAL SySTEMS .•...•....•
CUSTOMER FINANCING .
ACCESSORIES AND SUPPLIES GROUP ...••
COMPUTER SUPPLIES
CUSTOMER SPARES
DECUS

12 GLOSSARY

13 INDEX

11 . '
11 · '

11·'

11·1
11·'
11.'
11·1
11·2
.. . 11-3
,,-3

"..
"..
"..

11·5

1
Preface

This technical summary is a detailed Introduction to all
aspects of the DECSYSTEM-20 - from the processors
and peripheral devices to the TOPS-20 software and
DIGITAL's support services. The technical summary Is pri-

marily intended for system programmers and computer
system specialists already lamUiar with computer hardware and software. However, it contains usefullnformatfon
lor application programmers, system managers, and syslem operators.

You are encouraged to read the technical summary selectively. Many of the system'S concepts and features are
repeated throughout the text In different contexts. You
m ight first skim through the summary to find those topics
that Interest you most or perhaps read the summaries that
appear at the beginning of each section. You can then start
with sections of Interest and know which section to refer to
when you come across references to concepts discussed
elsewhere.
If you are familiar with computer Industry terminology and
simply want an overview of the DECSYSTEM-20 features,
you should read Section 2, Overview. It briefly describes
the DECSYSTEM-20 characteristics and Introduces features of the system that are described In detail In the rest.

Some people may find It more helpful to begin with Section 3, The Users. It Introduces many of the aspects of the
system that support application programming, system
programming, system management, and operator control.
If you are an application programmer, you will lind that the
sections on high-level languages, data management, and
application products provide an Indepth discussion on the
system'S characteristics and capabilities.

Finally, whether you are considering purchasIng a system
or have a system already, you should read SectIon 11,
Support Services, to become familiar with the kinds of
services DIGITAL makes available to Its system users.

,-,
.

2
Overview

DECSVSTEM-20 computers are multipurpose systems that provide a
wide range of computing versatility and power combined with
exceptional reliability and efficiency. The systems have buill-in
protection mechanisms In both the hardware and software to help
ensure a high degree of data integrity and system availability. Online
diagnostics and error detecting and logging verify system Integrity.
Many hardware and software features provide rapid diagnosis and
automatic recovery, should the power, hardware, or software fall.
The processors have a 36-bit architecture, and their Instruction set Is
implemented in microcode. All instructions are capable of addressing
up to 256K words of memory without resorting to base registers,
displacement addressing, or Indirect addressing. The large Instruction
set allows for the construction of efficient programs and access to a
wide range of operating system functions.
The operating system that runs on the DECSVSTEM-20 series of
computers is TOPS-20. Easy to use, TOPS-20 provides a highly reliable
virtual memory, multipurpose operating environment. It supports
multi language timesharing for program development and flexible
forms of interactive and terminal-oriented applications, In addition to a
full capability multlstream batch system.
The operating system is both flexible and extendable. It enables the
programmer to write large programs that can execute In both small and
large physical memory configurations without the programmer having
to define overlays or, later, modify the program to take advantage of
additional memory.

DECSYSTEM-20 computers are slate-ol-the-art hardware
and software systems. They serve Interactive timesharing
users, provide communications, and perform multiprogramming batch processing simultaneously. Because of
the systems' versatility, they can be used for a variety of
applications, such as:
• Commercial applications that require InteractIve data
access, a variety of data types, online data editing. data
Integrity, and high throughput
• Scientific applications that require large storage capacllies and high-speed computational capabilities
• Communications that require a large number of interaclive terminals and fast response

Processor.
The Kl10 and KS10 central processing units (CPUs) form
the basis of DECSYSTEM-20 com'puter systems. Both
CPUs provide 36-blt addressing, eight sets of 16 fast general purpose registers, and seven priority Interrupt levels.
Both CPUs feature a microprogrammed Instruction setcapable of directly addressing up to 256K words of memory.
TOPS·20 on the KS10 supports from 256K to 512K words
of main memory. and. on the Kl10, from 256K to 2.046K
words of main memory.

The design 01 DECSYSTEM-20s easily accomodates expansion and the incorporation 01 new features. devices,
and technology. likewise, TOPS-20 Is software-compatible In that programs that run on one version of TOPS-20
will operate on subsequent versions of TOPS-20 software
without any program modifications.

On the Kl1 0, the PDP-11-based Console/Diagnostic frontend computer plays a key role In the operation and
maintenance of the system. This minicomputer provides
all console and command terminal functions, Interfaces
with the various peripheral de.... lces. and performs all diagnostic and maintenance functions for TOPS-20 and the
Kl10.

Cache memory on both systems provides a faster effective
memory access time. The cache Implementation for the
KS10 is 512 words and for Kl10 Is 2,046 words.

DECSYSTEM-20s can supervise themselves primarily
because of the hardware Interrupt system and the TOPS20 operating system. Their combination allows for rapid
response to dynamic conditions both Internal and external
.to the system. When an error occurs, the current context Is
saved , the Interrupt is processed, and the saved context Is
restored, allowing the contlnuallon of normal operation.
Thare are multiple interru pt levels so that more Important
interrupts can interrupt less Important ones. Also. there Is
a special set of fast accumulators used at Interrupt level.
that make it unnecessary to save and restore the accumulators associated with the running context.

On the KS10, the 6-blt microprocessor console Is an extremely important subsystem because It performs all console functions and controls all diagnostic functions. Unit
record equipment and communications are handled by a
UNIBUS Adapter (UBA), which also controls the synchronous lines and the tape drives.
Both CPUs support KliNIK, the remote diagnosis
capability that equips Field Service Engineers to examine
the system while normal system operation continues.

A variety of Input/output devices can be connected to
DECSYSTEM-20 computers. The hardware features highspeed data channels, mass storage controllers for disk
and magnellc tapes, and communications controllers.

TOPS-20 Operating System
TOPS-20 Is a virtual memory operating system designed
for many applications, Including computation, data proceSSing, transaction processing, program development,
and batch processing. Some of the features that contribute to TOPS-20's versatility are:
• a multiuser, multiprogramming environment;
• interactive processing that ellows for simultaneous sharIng of system facilities by many users;
• multiple high-level language processors, two easily used
but powerful text editors, and many system utilities;
• a multislream batch system;
• an easily learned and used command language which Is
common to both the Interactive and batch users;
• online help facilities for commands and programs;
• a multiprocess job structure with a virtual memory ad·
dress space of 2S6K words for all processes;
• a sophisticated, reliable, hierarchicalllle system that includes file sharing, lIIe protection, file mapping, and file
backup facilities.

COMPONENTS
The major components of the DECSYSTEM-20 are the:
• Processor - Includes the choice of two models of CPUs
that run the TOPS-20 software: the KS10 and Kl10. Both
processors use the same Instruction set and support
Metal-Oxlde-Semlconductor (MOS) memory.
• Peripherals - Include a range of disk drives with smail
and large capacity, magnetic tape systems, hardcopy
and video terminals, IIneprinters, cardreaders, and papertape reader/punch.
• Operating system - Includes a virtual memory manager, a pager, a swapper, system utilities, device drivers, a
liIe system, a command language, and operator and
system manager tools.
• languages - Include TOPS-20 MACRO assembly language and, optionally, FORTRAN, COBOL-58, COBOl74, BASIC-PLUS-2, ALGOL, APl, CPl, and BlISS-36.
Development tools for both natlve- and compatlbilltymode programs Include editors, linkers, and de buggers.
• Communications - Includes DECnet-20 software, IBM
emulation and termination software for 2760/3760 and
HASP stations, and ARPANET software.

TOPS-20 provIdes a command language that Is
Interactive, comprehensive, easy to use, and extremely
flexible. II enables the user to log into the system, create
and manipulate flies, develop and test programs, and obtain system Information.
2-1

for each phase, programmers can overlap the phases of
the program and thereby decrease the execution time of
the overall program.

The Interactive user who Is not lamillar with TOPS-20 can
type a ''1'' (question mark) at any point within a TOPS-20
command to request help. For example, II a user types a
"COO followed by a question mark, the command language
processor lists all TOPS-20 commands beginning with the
letter "C." It then reprints the line up to the question mark
so that the user can continue, without starting over, with
the desired command.

TOPS-20 uses this process structure In the Implementation of Its own supporting software. As an example, the
command language processor Is a process within the
user's address space. Not only Is the operating system
smaller, because the command language Is not part of It.
but this design allows a job's command processor to control a process which Is Itself another command processor.
New or special command language processors can be
written, tested, and used during normal system operation,
just like any other system program. Of course, for the user
who does not require such a process structure, Its sUppOr1
by the system is Invisible.

The user can give a abbreviated portion of a command
and then press the "ESCAPE" control key on the terminal.
If the abbreviation Is unique, the command language processor will display the remslnder 01 the command along
with guide words to prompt the user for the necessary
arguments. This feature, called Command Recognition, also works on command arguments, on file specltrcatlons,
and on user names.

Both file space and process space are Integrated. Users
having sophisticated needs, such as those with multiuser
database applications, can simultaneously and efficiently
access and update flies, fully assured they are working
with the latest data. Unlike other systems, when a TOPS-20
file Is properly updated, It Is the file Itself, not a copy, that Is
modified.

TOPS-20 also provides the user with help facilities that can
be invoked simply by typing " help," followed by the program name or command name In question.
TOPS-20 provides a flexible, easy-to-use, powerful batch
processing system that Includes Input spoolers, batch
stream controllers, a queue manager, a task scheduler,
and output spoolers. Batch Jobs can be initiated and monitored from any terminal or can be automatically submitted
by the system at specified times.

The TOPS·20 file system Is a general purpose, named file
system that provides mountable disk structures, multilevel
user directories, optimized tile placement and 110, and a
file archiving and retrieval capability that's under user and
operator control.

Both Interactive users and batch users work with the same
command language. This feature is Important because It
facilitates the use of either mode of processing. Equally
slgnlficant Is that time Is saved, since users need learn only
one set of commands for both interactive and batch processing.

The TOPS-20 llIe system has been designed to provide
controlled sharing of programs and data flies. System efficiency is maintained by allowing for several users to simUltaneously access a single copy of any program. However,
TOPS-20 has built-In mechanisms to protect the system
and the users from the errors of other users. If a user Is
reading a file or executing a shared program, and If another user attempts to write In one of the shared pages, the
user doing the writing is given a private copy of the page
and proceeds with modifying the page. This feature, callecl
"copy-on-wrlte," Is automatically handled by the system.
TOPS-20 provides the file facUlties that equip users to create, access, and maintain fully protected data flies. The
flexible tile facilities enable a wide variety of file
organizations to be used, Including sequential, relative, Indexed sequential, and database organizations.

The operating system Is organized around a relatively
small amount of directly accessible main storage and a
large amount of high-speed secondary storage. All programs are organized in pages of 512 words. Such organization, which Is transparent to each program, means
users need not concern themselves with how memory will
be allocated In main storage or how pages will be swapped
between main and secondary storage. Assisted by the
hardware, the operating system transfers pages between
main storage and secondary storage as required, without
explicit Intervention on the part of the program or user.
The operating system provides a demand -paged memory
environment. Every job on the system can be considered
as a set of processes. These separately schedulable
processes are linked together by user options or systemdefined linkages, for efficient use of storage and system
resources. Operating In a demand-paged mode, the system moves Into memory a subset of all pages needed for
each active process, bringing pages In from - or moving
pages to - the disk as required. The system provides for
easy, efficient communication among processes, both at
the command and system level.

TOPS-20 support for many optional high-level programming languages provides flexibility in choosing the most
effective or most famUiar language for use In a given application. To minimize memory requirements, all language
processors are sharable and generate sharable code. Job
control , command languages, and the language processors are compatible under timesharing and batch
processing .
TOPS-20 optionally provides three types of communlca·
tlons software:
• DECnet-20, which extends the facllities of TOPS-20 so
that processes can communicate with other processes
In a DIGITAL computer network;
• IBM Emulation/Termination, which performs both emulation and termination of IBM 2780/3780 remote stations
or HASP workstations;

With TOPS-20, processes are able to Initiate, suspend,
and communicate with other processes. This structure allows for modularity In program development that can be
taken advantage of at execution time by segmenting programs into distinct phases. By using a separate process

2·2

The system operator can perform software maintenance
activities without having to bring the system down for
stand-alone use. Concurrent with normal activities, the operator can back up disks and run restoration procedures
for all tiles on the system or just a single file.

• TOPS-20AN, which allows a usar to communicate with
other sites or users on the Advance Research Project
Agency Network (ARPANET).

RELIABILITY

The operating system supports online peripheral diagnostics. TOPS-20 logs CPU errors, memory errors, peripheral
errora, and software failures. The operator or Field Service
engineer can examine and analyze the error log file while
the system is In operation.

DECSYSTEM-20 computers provide features needed for
maximum system reliability. Built-In reUabllity for both
hardware and software provides data Integrity; Increased
uptime; and fast system recovery trom power, hardware,
or software failures. Some of the features that contribute to
this reliability are discussed below.

System Recovery
Automatic system restart 'aclilltes bring up the system
without need 01 an operator after 8 system failure caused
by a power interruption, a machine check hardware malfunction. or a fatal software error. TOPS-20 automatically
performs machine checks and Internal software consistency checks during system operation.

Software De,lgn
TOPS-20 Is designed to easily and efficiently serve many
users and, at the same time, to be protected from possible
user errors. For example, the TOPS-20 command language processor Is the controlling process In each user's
Job. This organization makes the overall system more reliable because a command error will affect only the job that
caused the error; other jobs continue processing in the
normal manner.

Using TOPS-20 remote diagnosis, DIGITAL Reid Service
engineers can run diagnostics. examine memory locations. and diagnose problems from 8 remote terminal. The
Field Service engineer who goes to the site Is prepared in
advance to correct the specific problem.

High reliability and security are necessary attributes of a
multiuser environment, and the sophisticated TOPS-20 file
system provides both. The file system allows controlled
sharing and protection among USers. Master Ille directories are redundant for Increased l1Ie system Integrity. File
read operations have priority over file write operations, so
the system can quickly satisfy page faults. File write operations are ordered to ensure that flies are correct and
remain In a consistent state. When operations on a file are
active, Index blocks and pointers are kept In memory for
speed. When the user Is notlfied that a tile Is closed, It has
been completely written to the disk.

Error Reporting
TOPS-20 provides an extensive error-detection and errorrecovery package to ensure maximum system availability
to the user. It also provides complete error reporting for
DIGITAL Field Service and Software Support personnel
and the customer's operations staff.
When an error Is detected , TOPS-20 gathers all pertinent
hardware and software information, Including whether the
error Is recoverable. It then invokes the recovery procedure and adds this Information to a disk file tor storage.
later. a program can read thia lIIe and generate reports
concerning the entire system or Individual components.
Additionally, significant operational events, such as
system reloads and changes In the system conllguratlon,
are recorded to assist the operations staff In monitoring
system perlormance.

The operating system's division of nonresident and resident portions allows for efficient use of memory and for
system functions to be logically divided for Increased reliability. Unique protective processor modes are employed to
effectively manage memory.
System Availability
The TOPS-20 operating system allows the hardware system to continue running even If some of the hardware
components have tailed. The system automatically determines the presence 01 peripheral devices on the system
when the system Is started. If the usual system bootstrap
device Is unavailable, the system can be bootstrapped
from another disk drive, from magnetic tape, or from a
floppy disk. If memory units are defective, memory Is reconfigured so that defective modules will not be referenced. Software spooling allows for output generation,
even If the normal output devices are not avallable.

Periodically, Field Service personnel gather summary Information from this error lIIe and use It to detect Indications of possible problems. Detailed reports about specific
errors frequenlly allow diagnosis of a problem and eliminate the need for running exhaustive diagnostics In a
stand-alone mode.
The error IIle can be backed up on magnetic tape to provide a complete history of system operation and quickly
pinpoint slowly degrading portions of the system long before serious problems develop.

2-3

The
Users

The DECSVSTEM-20 consists of hardware and software that equip
users to run a variety of programs efficiently and conveniently. The
system is designed to execute many different kinds of Jobs
concurrently.
The DECSVSTEM-20 provides a complete program development
environment. In addition to the native-mode assembly language, it
offers optional high-level programming languages commonly used in
developing scientific and commercial applications. It also offers the
BLlSS-36 implementation language for system programming
applications. The DECSVSTEM-20 provides the tools necessary to
write, assemble or compile, and link programs, as well as build libraries
of source and object modules.
The system's general users are those who interact with applications or
system programs from an online terminal or who benefit from
executing batch jobs. These users can control the operation of the
system through the command language. This language also can be
used by system programmers to develop application software, by
operators to monitor the system, and by system managers to control
resources of the system.
The TOPS-20 operating system takes maximum advantage of system
throughput capabilities, allowing many independent users to
simultaneously share system facilities. Its rapId-response nature
makes It particularly well suited for a wide range of tasks.

Application Tools
Some of the tools available to the application programmer
are:

This section looks at the system 'rom four different user
perspectives:
• Application programmers
• System programmers
• System managers
• System operators

Record and File Handling - The record- and lIIe-handllng services provide general record and file-handling capabilities to users of high-level languages. Programmers
can include statements In their programs that can read,
write, find, delete, and update records within Illes. Records
can be of fixed or variable length. The programmer can
choose the best file organization and record access
methods for the data processing application.

THE APPLICATION PROGRAMMER
The application programmer can write, compile, and test
programs both interactively and in batch mode. As an in·
teracUve user, the application programmer can control the
running 0' 8 program; create, edit, and delete data Iiles;
compile, execute, and debug programs; request assignment of peripheral devices, such as magnetic tapes; and
make use of all system features from a terminal. As a
batch user, the application programmer can submit a Job
into the system. using a card deck that contains control
cards defin ing the command options and error-recovery
procedures for the job or, using a terminal, the user can
create and submit a control Ille that Is then Interpreted by
the batch system and processed In exactly the same manner as the job submitted on cards.

For additional Information on record and lile handling and
the system 's data management techniques, reler to the
section on Oata Management and Application Products.
Databas. Management - DBMS Is DIGITAL's proven
CODASYl-standard database management system .
DBMS enables programmers and managers to organize
and maintain data In efficient structures, so It can be
quickly and easily accessed by users and application programs. DBMS Is an optional software product. Aefer to
Section g for a detailed explanation of the DBMS software
product.

Programmers can use the system for development even
while other user jobs are In progress. All DECSYSTEM-20
languages and compilers are shared and reentrant, so
many programmers can develop programs in the same
language or in different languages without overburdening
the system .

Tran .. cllon Processing - The interactive transactIon
processing capabil ities of TOPS-20 are supported by
TAAFFIC-20, DIGITAL's Transaction Aoutlng and Forms
Formatting in COBOl.
TAAFFIC-20 simplifies building easy-to-use transaction
processing COBOL applications that let the computer
guide the user through each transaction. It is not necessary for the user to learn system commands. The application
can be written so that the user simply IIl1s out a form on the
terminal screen. In effect, TRAFFIC-20 makes nonintelllgent terminals appear to be Intelligent terminals that can
display a form or a series of forms.

The Progremming Languages
Languages offered on the OECSYSTEM-20 are:
• COBOL, the recognized " big machine" bUSiness Ian·
guage. DECSYSTEM-20 COBOL provides extensive data processing capabilities for commercial applications. It
is written to the ANSI 68 or 74 specification, so it matches the COBOL used on most general purpose systems.
• FORTRAN, the standard scientific languege. DECSYSTEM-20 FORTRAN consists of a globally optimizing
com plier and runtime system with an Interactive debugger to provide fast program development and execution.
• ALGOL, a sophisticated scientific programming language. DECSYSTEM·20 ALGOL is a one-pass, singlephase compiler that generates optimized object code.
• BAS1C-PLUS-2, an easy-to-learn conversational programming language. BASIC-PlUS-2 uses familiar English words, abbreviations, and mathematical symbols
10 perform operations. Conveni ent data structures,
Includ ing multi-key Indexed flies, can be easily created
and efficiently accessed with BASIC-PLUS-2.
• APl, a concise programming language suitable for
man ipulating numeric and character-oriented , arraystructured data. It includes procedural operators for array calculations and Its own editing and debugg ing facilities.
• CPl, an interpreter supporting a subset of the ANSI
PLII language.
• BlISS-36, DIGITAL's implementation language for software development It contains many 01 the features of a
hig h-level language, yet It also provides the flexibility
and access to hardware of assembly language.

Used with the DBMS system , TRAFFIC-20 makes it easy to
bulld lIexl ble, Integrated , multiuser applications that Include specialized screen formats lor data Input. Because
the DBMS system Is Integrated Into COBOL. several transactions can access and update Illes at the same time. Data
Integrity is ensured . Centralized data definit ion Is
supported.

THE SYSTEM PROGRAMMER
The system programmer can design and develop application systems for multiprogramming environments requirIng fast response and a high degree of Job Interaction and
data sharing.
System programmers are provided with a range of tools
lor developing high-level languages, system utilities, and
application systems where the sophisticated features of
the operallng system are required .
MACRO , Ihe TOPS-20 symbo lic assembly language ,
makes machine language programm ing easIer and faster
by translating the symbolic operation codes In the source
program Into binary mach ine language Instructions. It relates symbOlS specified by the user to stored numeric values and It assigns relative core addresses to symbolic addresses of program instructions and data.

3·'

System programmers can also use BlISS·36 for software
development. BlISS-36 Is an optimizing, hlgh.level sys·
tem Implemenlatlon language for TOPS-20 . Ills
specifIcally desIgned for buildIng compliers, syslem utilitIes, and operatIng system software.
System programmer applications normally communicate
with the system through monItor calls. MonItor calls are
used to request system functions, such as Input/output
operations, error handling, and number conversions, durIng execullon of the program. Support programs, such as
the COBOL complier, Issue requests to the system
through monitor calls. All monitor calls are reentrant, to
maximize system reliability by IsolatIng monitor-cali proc·
esslng from operatIng-system processIng .
Through TOPS·20 mon itor calls, users can access a variety of sophIsticated operating system fUnctions - for ex·
ample, the TOPS-20 command processor. Applications
can be written that have the same syntax, help facilities,
and recognition features used at system level.

Each user who wishes to access the system is esslgned a
user name, password, and account name. When the user
logs Into the system. the system verifies the user's name
and password. If either Is Incorrect. the system refuses the
user access, Ihereby protecting itself from unauthorized
use.
The system manager can assign a delault account name in
the user's directory SO that the user does nol have to enter
an account name when logging Into the system.
Privileges
The system manager can assign Individual users special
privileges that cover dIrectory access, resource usage,
and system operational control.
If a user tries to execule a function that requIres a specific
privilege, the system checks the user's directory parame·
ters to see If the user Is allowed that privilege. If the user
does not have the specifIc privilege. the system does not
execute the function and Instead notifIes the user of denIal
of that prIvilege.

Allocating Disk Storage Quotas
The syslem manager assigns each directory a specific
number 01 pages for both working slorage and permanent
storage, Work ing storage refers to the disk space that 8
user can have while work ing on the system . Permanent
storage refers to the total disk space In which a user can
store flies after logging off the system.
The system strictly enlorces working storage allocation. It
will not allow a user to create a new file If that individual's
work Ing storage has been filled.
Controlling Resources
Through a user-wrlnen program. the system manager can
make policy decisIons thai govern access to a specific
system resource, For example. TOPS·20 allows a user to
change the speed of a terminal, assign a device. log Into
the system at any time. mount a magnetic tape, and mount
a disk structure. Access conlrol enables the syslem manager to restrict or disallow the use of some of these faclll·
ties. The syslem manager can grant certain users access
to the system at specified times of the day and , "desired,
at specified termInals. By usIng the access control mechanism, the system manager can reduce or prevent mall·
clous access to Ihe system resources and has an
additional means for collecting accounting or other informallon,
Scheduler Contlols
The system manager Is provided tools that enable control
or tuning of the allocation of CPU lime, The tuning mechanisms Include class scheduling and bIas control.

THE SYSTEM MANAGER
The system manager Is responsible for planning data access and protection, granting privileges, authorizing use of
the system, controlling resource utilization, and analyzing
the system's accounting and performance Information ,

Using class scheduling, the system manager can allocate
percentages of the central processor's time to Individual
classes of users to provide consistent service. Each Job In
a class receives a portion of the class percentage. The
system manager can also set up a class to Include all
batch jobs, thereby controlling batch jobs separately from
Interactive jobs,

User Authorization
The system manager controls use of the system primarily
by creating user directories that Identify the user, supply
defaults, specIfy privileges, and limit resource usage.

3-2

Class SCheduling Is dynamic, and changes made during a
session remain In effect until the system Is reloaded or
another change Is made. Using TOPS-20 commands, the
system manager can turn the class scheduler off and back
on again while the system Is In operation.

operating the entire system and Is provided with command
recognition, guide words, and help text.
Controlling Batch Strellm.
The system operator can control the number of batch
streams that can run concurrently. Batch Jobs can be submitted by Interacllve users, other batch jobs, or programs.
When the number of jobs exceeds the number of streams,
the overflow is held in 8 batch Input queue. The operator
can start additional batch streams, If desirable, and can
also stop, continue, and shut down batch streams. The
operator can send messages to batch streams, set parameters for batch streams, and dIsplay the status and parameters of batch streams.

By using the bias control feature, the system manager can
direct the scheduler to favor either Interactive or computebound programs. The bias control feature Is analogous to
turning a knob over a range
settings. When a low number Is selected, the scheduler favors users running Interactive programs. When a high number Is selected, It favors
users running compute-bound programs.

Bias control and class scheduling can be used simultaneously.

SYlltem Recovery
The system operator can select manual or automatic system recovery following a power Interruption or a hardware
or software failure.

Resource Accounting Statistics
Computer use can be assigned and charged to various
accounts via the aet:ounting facility. Using this feature, the
system manager can add security to the system; determine charges for computer usage and bill users by
account name; and associate classes with accounts for
use by the class scheduler.

On automatic system recovery, after a power interruption,
the system determines whether the contents of memory
are stUl valid . If they are, it restarts all possible I/O In
progress at the time of interruption and continues operation from the point 01 Interruption. If the contents of memory are not valid , the system automatically restarts Itself
from disk and executes startup command procedures.

All accounting data Is stored in a usage file that can be
accessed for reports and billing. Because the system colleets detailed data In reeord format, the system manager
can define algorithms used In resource usage bllllng.

If the standard system bootstrap device Is unavailable, the
operator can boot the system from one of several different
devices.

Performance Analysis Statistics
The Performance Analysis Statistics program collects system usage and performance data that can be used to tune
the system. Some of the statistics gathered by the programare:

System Backup
All files or selected flies can be saved on tape. The system
operator can use this tape to restore all or certain files
back on to the disk .

• Monitor statistics Indicating CPU , disk, memory utlllzatlon, and system performance:

If the system Is using the archiving/migration feature, the
operator can periodically run a program to copy all archived or migrated files to tape.

• Job ststrstics Indicating CPU time used by each job,
information on each Job's use of system resources, and
statistics collected on the Individual jobs;

• System utilization stetlstlcs Indicating the demands
made on the system and the distribution of system resources;
• Disk 110 statistics indicating the number of seeks, reads,
and writes performed by each disk drive.

USER UTILITIES
The TOPS-20 operating system features several utility programs that aid the user In performing various tasks. The
most frequently used utilities are:
• A MAil program with whIch the user can send messages to other users. Messages sent by the MAil program are stored in the receiver's disk directory and can
be read at the receiver's convenience.

THE SYSTEM OPERATOR
The system operator has complete control of the system.
Operator responsIbilitIes Include readying the system for
tlmesharing and batch work , responding quickly to user
requests such as magnetic tape mounts, taking care of the
peripheral devIces and the distribution of output, and recovering the system when error conditions occur. The system operator can be called upon by the system manager
to perform a variety 01 other functions, related to both
hardware and software, to ensure the efficient running of
the system .

• A RDMAll program to read the messages sent by the
MAil program.
• A PLEASE program by which the user can communicate
with the system operator.
• A CREF program to generate a cross-reference listing of
symbols used in programs.
• A FllCOM program to compare two files on a line-byline or word-by-word basis and list the differences.
• A MAKUB program that manipulates, changes, and
queries reiocatable binary flies. MAKUB Is mainly used
to manipulate and optimize collections of binary programs Into libraries.

Operator Interfllce
The OPR unified system Interface enables the system operator to deal with all the batch system components,
handle user requests, and monitor application control programs. The operator learns a single set of commands for

3-3

• A DUMPER program that lets the user copy disk tiles to
magnetic tape for safekeeping and/ or to transfer flies
between systems. DUMPER can be used by the system
operator to perform lull or incremental system backups.
It can also be used by system users to back up selected
flies .
• A LINK program to merge independently complied program modules and system modules Into a sIngle module
that can be executed by the operallng system .

• A DDT program that lets the user examine, search,
change. Insert breakpoint Instructions, and stop/trace a
program at symbolic level. The user can also single-step
executable programs.
• An EDIT program with whIch the user can create and
modify line-oriented programs and data files online.
• A TV program with which the user can create and edit
any source documents, programs, or other text liIes.

3-4

4
The
Operating
System

TOPS·20 Is a highly reliable operating system designed to provide a
wide range of services to users of varying capabilities. After brief
training In using the command language, even novices can easily use
the syslem. The same command language serves both interactive and
batch users.
TOPS·20 provides a demand·paged, process·structured environment.
Every job on the system is made up of one or more processes, each
having Its own address space. Operating In a demand·paged mode,
TOPS·20 moves into memory a subset of all pages needed for each
active process and moves onto disk all pages not currently required.
The virtual memory design of TOPS·20 minimizes the use of main
memory because only the currently necessary functions and data
reside In memory. User programs are handled in the same manner,
with nonactive pages residing on disk. Pages are moved Inlo memory
when needed, so the program can execute whenever the processor
calfs for It. This dynamic allocation does not require user Intervention; It
is Jointly handled by the hardware and the software.

TOPS-20 is designed for interective processing and for
many independent users simultaneously to share system
faCIlities. TOPS-20's rapid response and versatility make It
par\lcUlarty effective over a wide range of tasks. Most
users communicate with the system through a terminal,
ttther at the central computer site, or at remote locations
connected to the system by communications lines.

Simply by typing a single command, users can display a1l
TOPS-20 commands or various system statistics - tor
example, terminal characteristics, system defaults, or
available devices. Users can send messages to, or receive
them Irom, other users; attach to another user's terminal;
set terminal characteristics; and so forth.

THE BATCH SYSTEM
TOPS-20 can concurrently execute batch jobs and time·
sharing jobs. The user can enter a job Into the batch system by creating and submitting a control Ille Irom a terminal or by using a card deck . Because the command language for batch and timesharing Is the same, the user can
duplicate any terminal session with a batch job by using
the same sequence of commands.

THE COMMAND LANGUAGE PROCESSOR
The user Interface to the system is the TOPS-20 Command
language Processor. It Interprets ali commands Issued by
the user for system services and sends responses from the
operating system back to the user's terminal. The Command language Processor, a user program residing in the
user's address space, is used for:

Switches provided with the batch system give the user
great lIexlblllty. Included in the command string, they can
define the operation and set priorities and limits on
memory and processor time. In addition, the user can
structure the job submission so that jobs execute in a particular order.

• Accessing the system
• Directory and liIe utility operations
• Initiating programs
• Initiating operations
• Acquiring Information about the system
• Debugging programs

Users can control the handling of error conditions by Including special commands in their jobs. It an error occurs,
and If the user has not specified any error-recovery procedures, the batch system InitIates a memory dump of the
user's area end terminates the job.

Because the Command language Processor runs as a
user program. an error found by it will terminate only the
}ob that caused the error.
DECSVST EM-20 owners can purchase Command language Processor source code. It can be modified, tested,
and debugged as a normal user program under timesharIng, The modified code can then replace the existing syslem version 01 the Command language Processor.

The batch system requires little or no operator intervention, although the operator can exercise control If II
becomes necessary. The operator can specify system resources to be dedicated to batch processing ; can limit the
number of Jobs, memory. and processor time lor Individual jobs; and can stop a job at any point, requeue II, or
modify Its priorities. The operetor and the user can examine system queues to determine the status of a1l batch
jobs. The batch system sends Information to the operator
and records on disk a log liIe 01 all messages printed on
the operator's console. A1I operator Intervention during the
running of a batch job Is recorded In both the user's log liIe
and the operator's log tile for later analysis.

TI'Ie Command language Processor permits a user to
lnterrupt a currently executing program, save Its address
space. and start another program. For example. If a user
neglects to create a necessary liIe before starting a program, the user can Interrupt the program that Is running,
return to the TOPS-20 command level, and save the program's address space and execution state. After creating
the necessary lile, the user can return to the IIrst program
at the point 01 Interruption and continue processing.

Running several batch jobs concurrently enhances syslem
and user throughput because a user can separate jobs
Inlo severel parallel subjobs.

The Command language Processor Is reentrant and sharable. Even though it Is shared by many users, only the
currently needed parts 01 the Command language Processor reside In memory.

Batch system programs Include the Input spooler, the
batch controller, the centralized queue menager, the task
scheduler. and the output spooler.

The TOPS-20 Command language Processor provides a
common command language lor interactive and batch
users. The command language uses English words to Invoke system functions. All TOPS-20 commands begin with
a key word and can be lollowed by parameters to fully
describe the lunction requested by the user. Users can
create, edit, delete, and undelete files; compile, execute.
and debug programs; and use all system features.

The input spooler reads the Input from a device, such es a
cardreader, disk. or magnetic tape, and requests the
queue manager to enter jobs Into the balch controller's
Input queue. The input is separated according to the control commands it includes, and is placed elther into the
user's data files, or Into the batch controller's controllile
for subsequent processing . The Input spooler creates the
user'S log tile and enters a report of lts processing 01 the
Job as well as a record of any operator Intervention during
the processing. This log liIe Is a standard part 01 the output
lor a batch Job.

To enable even a beginner to use the system successlully.
the command language contains such features as guide
words that prompt the user, recognition input that uses
command delaults to complete commands, and heip lacillties that provide instructions about programs and commands.

The centralized queue manager Is responsible for scheduling jobs and maintaining both the batch controller's

'-1

PROCESS COMMUNICATION

input queue and the output spooling queues. A job Is
scheduled to run according to external prioritIes, processing time limIts, and parameters specified by the user for
the Job. The latter can Include start and deadline time limIts for program execution.

A process can communicate with other processes in the
system in several ways:
• Direct process control
• Interprocess Communications facility
• Software Interrupts
• ENQueue/ DEQueue facility
• Memory Sharing

The output spooler improves system throughput byallowing the output from a Job to be written to a disk lor later
transfer to the lineprinter. The queue manager places the
job's log !lie and output into one or more output queues to
await spooling. When the lineprinter becomes available,
the lineprinter spooler processes the output. This spooler
also has fealures such as special forms control and character sets, multiple copies, and accounting information.
The output spooler and lineprinter spooler are also used
by the InteraC1lve user 10 get a printed Ilstlng of a flte.

Dlract Proca •• Control
A process can create and control other processes Inlerlor
to Itself within a jOb structure. The superior proceS! can
begin , suspend, and resume execution of the Inferior
process. Alter the Inferior process has completed Its tasks,
the superior process can delete It from the job structure.
Interproce.. Communication Facility
Although aach process Is fundamentally Independent, an
important advantage of a multiprocess job structure Is that
Ihe output of one process can be used as Input to others.
The Interprocess Communication Facility (IPCF) enables
fast communlcallon among processes. Communication
occurs when processes send and receive Information In
the form of packets (messages). Each sender and receiver
has a unique process Identification number assigned to It
that Is used to route packets among processes.

JOBS AND PROCESSES
The TOPS-20 operating system distinguishes between a
job and a process. When a user types a CONTROL C at a
terminal, the system creates a job by invoking the TOPS20 Command language Processor. During the existence
of the Job, the user issues commands and executes
programs. The system terminates the job when the user
logs 0" the system.
Each job can have multiple, helrarchlcally organized
processes. When a job Is created , It consists of one process containing the Command language Processor. Whenever the Command Language Processor cannot perform a
requested function, It creates an Inferior process to do so.
The creating, or superior, process has complete control
over its inleriors. It can give or withhold privileges, and
suspend, conlfnue, or term inate them. Processes communicate with each other using a Process Identlllcation
Number (PID) that Is unIque for each process In the syslem. In this tree structure, the top-level process In a job Is
usually the TOPS-20 Command language Processor.

When one process sends Information to another, It Is
placed Into the receiver's Input queue, where It remains
until the receiver retrieves It. Instead of periodically checkIng Its Input queue, the receiver can aC1lvate the software
Interrupt system so that it can be Interrupted by the sendIng process when the information has been sent.
To use IPCF, the system administrator must assign a user
quotas that designate the number of sends and receives
the user's process can have outstanding at any lime. II a
user has a send quota of two and has sent two massages,
for example, the user cannot send any more until at least
one message has been retrieved by Its receiver.

Each process Is separately scheduled, has Its own 256K
address space, and competes for system resources such
as the CPU and the devices. Th is makes the system more
responsive to demands and It more easily achieves the
goal of appearing to simultaneously perform a variety of
functions.

Softwere Interrupt Sy.tem
The software Interrupt system enables a process to respond to several types of Interrupts generated by other
processes, such as hardware error conditions or terminal
trensactions. Interrupts can be activated either by a user
or by the system . The system provides 36 software Interrupt channels, 01 which 18 have reserved functions. The
primary types of interrupts are:
• Terminal charaC1er Interrupts
• IPCF Interrupts
• ENQ/ DEQ interrupts
• Hardware error condition Interrupts
• 110 error-condition Interrupts
• Program errors (such as arithmetic overflow)
• Interprocess Interrupts

Before a process can be scheduled by the system It must
be in a runnable, or active, state. One requirement for this
Is that a subset of Its pages needed for execution, called
the working set, is in memory. The collection of processes
most eligible to run and whose working sets
simultaneously fit Into memory is caJled the balance set.
Processes that are not runnable are inactive because they
are waiting for events such as terminal Input. These inactive processes are blocked until the required event occurs.
Because the runnabillty of a process Is event-driven It
changes whenever the state of a process changes. To ensure good response, Interactive processes tend to get
higher priority than compute-bound processes. However,
If a computa-bound process has been blocked for a long
time, Its eligibility Is changed to allow it to run.

For priority ordering, there are three Interrupt priority
levels assignable to each software Interrupt channel. A
system call Is provided lor Interrupt dismissal to resume
the Interrupted code.

4-2

EnqueuelDequeue (ENQ/OEQ)
TOP$-20 makes program and data sharlng very easy,
whlla preventing any user from changing a file that others
are using In read-only mode. Howevar, more complex applications require simultaneous updating of a database
(file) or sharing of devices.

THE TOP5-20 MONITOR
The TOP$-20 monitor Is a collection of modules that provides overall coordination and control of the lolal operatIng system. The monitor permits several user programs to
be simultaneously loaded Into memory. It makes optimum
use of the timesharing hardware to prevent one user's
program from interfering with other users' programs. A
sophisticated scheduling routine handles the requirements for execution, memory, and system resources to
provide good response lor interactive users, and high
throughput for computational users. The scheduler selects
processes to run based on class, internally computed
prlorlttes, and external policies. It makes these selections
frequently enough for all processes to seem to run simultaneously.

By using the ENQ/DEQ faCility, cooperating processes can
ensure that such resources are shared correctly and that
one user's modifications do not Interfere with another's.
Examples of resources that can be shared using this facility are devices, flies, operations on flies (e.g., READ,
WRITE), records, and memory pages.
Memory Sharing
Each page in a process' address space Is either private to
the process or shared with other processes. Pages are
shared among processes when the same page Is represented In more than one address space. This means that
two or more processes can Identify and use the same page
of physical storage. Even when several processes have
ldentitJed the same page, each process can have a different access to that page, such as access to read or write
that page.

Another function of the monitor Is to process Input and
output commands. The monitor's Input/output service
routines preprocess the data so that all devices appear
identical to the user's program, thus simplifying coding .
The monitor uses the software Interrupt system to overlap
Input/output operations with computation operations. For
Instance, If a user's program must wait for completion of
an input/output operation, the monitor will automatically

4-3

The specific goal of working set management Is to swap
working sets Into and out of memory based on working set
historieS and current memory allocation. To run, a process
needs Its working set In memory; therefore, the working
set manager always attempts to have the working sets of
runnable processes In memory. This aids throughput by
keeping the CPU active with useful work. Some definitions
are needed to understand the working set manager:
• Preloadlng - The action of swapping the working set 01
a process Into memory upon the selection of the process
to be run.
• Postpurglng - The action of completely removing the
working set 01 a process when the process has been
selected to be swapped out to secondary storage. If
postpurglng Is not In effect. the pages of the process are
swapped out 01 memory one page at a lime as other
processes need the pageS.

switch to another user's program , taking advantage of the
system's throughput capabilities.
The TOPS-20 monitor is modular and paged. It can be
tailored to each user's equipment configuration and application requirements. Extensions to the system In the form
01 peripheral devices and appllcatlon programs can be
added , altered, or deleted as required, without any change
to the monitor.
In summary. the monitor exercises primary control of the
routines that constitute the operating system . This makes
the computer a flexible tool that provides the user with
maximum use 01 the hardware's advanced design features.

VIRTUAL MEMORY
From a hardware view. memory Is divided Into sections of
256K locations. The paging hardware further divides each
section Into 512 locations, For the most part. virtual memory Irom TOPS-20's view is the same as from the hardware's view. TOPS-20 incorporates features that make
virtual memory more appropriate lor the end user. Users
have a 256K word address space In which to place programs and data. TOPS-20 divides the user's space Into
512 pages, each of which contains 512 36-bll words.

Part 01 the working set manager's decision to swap a workIng set in or out of memory Is based on the current memory allocation. Membership in the balance set indicates that
a process has been allocated memory. For this reason. the
working set manager selects only a member of the balance
set to be swapped Into memory.
The other part of the working set manager's decision to
swap a working set In or out of memory Is based on a value
represenllng the history 01 a process. This value is calculated from the current state of the process and its recent
behavior. The state of a process includes whether It Is
runnable and Its current queue location . The recent behavior of a process Is related to Its membership In the
balance set.

Virtual memory addressing Is accomplished through the
indexed accass method . Section tables exist for each
process. and paga tables for each section. These page
tables contain pointers to pages that contain either addltlonatlables or the data. There are lour types 01 pointers:
no access, Immediate. shared, and indirect.
The paging hardware maps pages from virtual address
space into pages anywhere in physical memory. A page
map for each process specifies correspondence from
virtual address to physical address, whether an Individual
vi rtual page Is accessible. whether it Is public or
concealed, and whether cache memory can be used to
refer to the page.

The work ing set of a process Is swapped Into memory
using one of two methods:
• It can have just Its overhead pages swapped In. As the
process executes, additional pages are faulted In as
needed,
• The working set Is preloaded. This method loads the
pages that were In the working set when the process was
last swapped out of memory.

VIRTUAL MEMORY OPERATIONS

The system manager decides whether to preload the
working set. A working set is always post purged when it is
removed Irom memory. All pages of the process are
swapped out of memory.

The TOPS-20 operating system provides a demand-paged
virtual memory environment. The system moves Into
memory a subset of all pages needed for all active
processes, bringing pages In from or moving pages to the
disk as memory space becomes available, The work ing set
Is that set of pages referenced during a recent interval of
time, that is, those pages recently used. The system determines the Interval so that, when the process Is reactivated,
memory references will most likely be confined to the
same pages. A particular program's characteristics determine the number of pages In Its working set.

The Scheduler periodically redefines the batance set.
Working set sizes are modified dynamically as a process
runs and they are regularly monitored by the Scheduler to
adjust balance set membership. If needed, a specific user
or group 01 users can be guaranteed a percentage of the
processor lime.
TOPS-20 supports memory management through hardware and microcode. Memory mapping and page-level access protection provide efficient sharing of pages between
processes and efficient context switching. Both page status and history lor each page in memory are automatically
updated by the microcode from information Initially set up
by the software, These updates create hardware tables
that minimize overhead while they maximize system informallon needed for management of memory and diskchanneltralflc.

A second definable property Is the balance set, the set of
processes most ellg lble to run and whose collective workIng sets fit Into memory.
The working set manager uses balance set membership to
determine whether a working set can be swapped into
memory. Balance set membership Is also used In calculating the history of a process.
4-4

r
In Indirect mode, the entry on the Shared Pages Tables
does not point directly to memory, but rather to another
entry in the Process Table. This other entry may relndex
back Into the Shared Pages Table or point directly to a
physical page.

To effectively manage memory. the DECSYSTEM·20 uses
a combination of registers and tables to relate program or
virtual addresses to physical addresses. Two hardware
registers in the central processor, the EBR and UBA, contain pointers to the physical pages In memory that contain
the mapping information for the operating system and the
currently active ussr. These pages, called the User Page
Table and the Monitor Page Table, contain pointers lor
mapping information between the user's and monitor's address space and the actual pages 01 physical memory in
use by the user and the operating system. Three types of
pointers contained in the process tables are Immediate,
shared , and Indirect. The characteristics of an Immediate
Mode Pointer are shown below. Entries in the User Page
Tabte point directly to physical pages in memory. Shared
Mode Pointer characteristics are also Illustrated.

To maximize system speed, the Hardware Page Table In
the CPU Includes a subset 01 the Information for all active
process page mappings, InCluding the operating system .
As the working set for a particular process Is generated or
altered , the page mappings obtaIned are loaded into the
Hardware Page Table. Subsequent memory references to
these pages then proceed through the Hardware Page Table, eliminating the need to access the In-memory page
tables. This high-speed Hardware Page Table minimizes
the need for an extra cycle to pick up the required
mapping information.

An additional register in the central processor points to a
memory status table that contains. for each page of physical memory, Information on recent references, page modi·
fications, reasons for a page to be loaded in memory, and
reverse pointer data. The operating system uses the mem·
ory status table to compute the length of time pages have
been active and in memory, to record when pages have
been written into, to record which processes have refer·
enced the page, and to locate which of the page tables
point to the page.

--~

THE FILE SYSTEM
The TOPS·20 file system is designed to provide the user
with the highest possible degree of operational flexibility in
storing and retrieving data. Because the system adjusts
the Interface between the file and the device, the user need
not consider the physlcai characteristics 01 the recording
device when creating most liIes. The system Invokes
security measures to help ensure that flies are not subject
to unauthorized use or destruction. Users have lacilities to
back up Illes from mass storage devices to magnetic
tapes, as well as to restore such files to the mass storage
devices when they are later needed .

~--

Files
A file is an organized collection of Information directed
toward a certain purpose. The TOPS-20 lIIe system Is a
collection of named files composed 01 512-word data
pages. Each file Is Identified by a node name, device,
directory name, filename, fl1 etype, and generation number
- all of which define a unique path to the file.

Agur.4-1
Polnt.r Mod ••

The shared·mode pointer Indexes into a Shared Pages
Table that contains entries pointing to physical pages In
memory. The location of the Shared Pages Table In memory is contained In another hardware register internal to
the central processor. The advantage of having a Shared
Pages Table is that, when multiple processes are sharing
the same page, the bookkeeping required to track the 10eation of the shared page Is reduced to updating only the
Shared Pages Table. Without a Shared Pages Table, every
user's Page Table, many of which would not be In memory,
would have to be modified. When one process writes on a
shared page, the system performs a copy-on-write , which
creates a process-specific copy of the page, Including the
modifications. Because the process Is using a modified
page. and no longer sharing the original page. the Shared
Pages Table Is updated to show one less user sharing that
page.

File Protection
A user who creates a file can either assign a protection
code or let a system default protection be assigned . All
Illes are assigned protection codes for each of three class·
es of users: the owner, users within a common group or
project, and all other system users. Members of each class
may be granted all , some, or none of the following:
• Acknowledgement that a file exists when listing the
directory
• Permission to append data to a file
• Execute-only access
• Write access
• Read access

4-5

Each tile Is associated with an Information block that fully
describes the file characteristics to the operating system.
The informallon inctudes the tile protection code, the awner of the·lUe. the name of the user who last wrote Into the
liIe. the date the file was created, the date the tile was last
changed. and the size of the file. The owner of a Ille can
change the protection code ot the file at any time. All user
filenames arB stored In a user file directory.
File Dlrectorle.
The TOPS-20 operating system maintains a Ille directory
lor each user. The llie directory contains the names 01 all
the user's flies, contains pointers to the user's file Informalion block, and contains general user information that Includes the user's password, privileges, disk-space allocation, disk space used, and default protection code. All file
directories are themselves named flies, and information
aboul them Is contained In a master directory called
ROOT -DIRECTORY. There are two copies of ROOTDIRECTORY to Increase file-system Integrity.

Ing simultaneously, using the TOPS-20 ENQueue/DEqueue facJllty for coordlnallon).
• Restricted Updating (one user writing , any number of
users reading).
As a further protection, If a user has opened a file for
reading or Is executing a shared program and attempts to
modify a page that other users believe is not changlng,the
user who wishes to modify the page Is given a private copy
of It. This automatic facility Is called copy-an-write.
Archiving Flies
The number of flies In a user's directory is constantly
grOwing. Consequently, the user may want to delete some
flies or store some offline on magnetic tape. TOPS-20
users can store fUes offline with a simple command. The
user requests a tile to be archived. and the system marks
the file for archiving, giving It archive status. The system
may then make the file Invisible to the user, even though It
has not yet been physically archived.
A file becomes archived when It has been backed up on
two tapes. The two tape copies provide Insurance In case
one of the tapes Is losl or destroyed by accident. An archival run consists of executing a system program to write
onto tape flies with pend ing archival requests. Thus, to
fully archive a file requires two archival runs. The system
administrator must decide when the two runs are P8fformed, either one after another or the first run one day
and the second the next.

The tree-structured directory facJllty allows the user 10 create subdirectories. Subdirectories appear to the system as
do file directories In that they can be accessed, can. be
members ot user directory groups. and have the same
protection mechanisms as fjle directories. The tree-structured directory facUity permits approximately 4,000 directories to be created on 8 KS10 system and 12,000 directories on a Kl10 system .
Groups
A group Is a set of cooperating users that is established by
the system manager. Each directory contains two
membership lists: the list of user groups of which the owner ot the directory Is a member and the lists of groups of
which the directory Itself Is a member.

An archival run Is performed In two phases. During the first
phase, all files In the range of the given l1Ie speclflcallon
are examined to see If the archival request bit Is set. When
a tile Is found with this bit set, the system proceeds to write
the file to tape. After the file Is written to tape, the search
continueS lor more archival requests. After the entire
range of the lIIe specification is searched. tlie second
phase begins.

File Us.ge
The prime concern lor users of the file system Is the mechanism that permits controlled sharing of programs and
data. The design of TOPS-20 ensures that two users with
access to the same program will share It automatically.
When either user modifies a page of the program, the
system gives that user a private copy of the page, unless
the two users expllcltly specify they wish to share the modIfied page. This facility makes memory utillzatlon far more
efficient, since many users can share a single physical
copy of any program. For example, although the TOPS-20
COBOL complier code is shared by all users, the users'
particular program statements are slored in separate
areas.

The second phase consists of examining tha tape Information for each of the archival request flies to determine
whether that Information Is valid and complete. The archive status is then adjusted accordingly. If the file has
been written to two tapes, and If the user did not specify to
retain the contents of the file on disk, the disk contents of
the file are deleted. Because the filenames are retained In
the user's directory, the user can request retrieval of the
files by filename. The llIe retrieval process uses the information In the file directory to identify the tape reel containIng the file.
rape Labelling
The TOPS-20 operating system supports the reading and
writing of ANSI- and TOPS-20-tabelled tapes, and the
reading of EBCDIC-labeled tapes. This support Includes
Automatic Volume Recognition (AVR) 01 labeled tapes;
reading and writing of labels; automatic record blOCking
and file searching; handling multiple-volume tape sets;
and fixed. variable, and spanned record formats.

Although program sharing is Important, data sharing Is
even more important when It comes to building effective
multiuser database systems, especially when online Interaction Is required. it can be confusing If one user is changing a particular file while another user Is read ing it.
To prevent this confusion the system offers several modes
of shared access:
• Shared Reading (one or more users reading, no user
writing).
• Writing (one user writing. none reading).
• Shared Updating (one or more users reading and wrlt-

CONSOLE FRONT·END PROCESSOR
On the OECSYSTEM-2040 and 2060, the console frontend processor and software reduce the central proces-

4·6

......

sor's participation In 110 opera tions and together serve as
I powerful diagnostic/ maintenance tool for service personnel. Specifically, they is responsible for providing :

tlng capability Is provided , enabling terminal speeds to be
changed dynamically . On dialup terminal lines , the
monitor wlll automatically select the appropriate rate for
110, 150, 300, or 1,200 baud lines when the user types a
carriage return or Control-C. Thus, line speeds need not
be associated with phone numbers.

• Console functions
• Interface for command terminals
• Interface for unit record peripherals
• Diagnostic and maintenance functions

Peripheral Interface
The unit record-spooling programs In TOPS-20 communicate with the console front-end processor, using the same
buffering mechanism described lor the command terminal
functions. Both the central processor and the console
front-end processor maintain buffers lor data. They Interrupt only once per buller transmission, Increasing the amount of useful work each processor can do.

Console Function.
Two major functions 01 the front end are system InlUallntlOl'1 and communication between the system and the operItor. A person need only push a button and type In data to
Inltlate the automatic program sequence In which the
console front-end processor loads and verifies the microcode, configures and interleaves memory, and loads and
starts execution of the central processor bootstrap program from a device specilled by the user.

DlagnostlcfMa,ntananca Functions
Remote diagnosis capability reduces mean time to repair
(MTTR) and increases system availability to the user, It
also allows DIGITAL's service engineers to determine the
causes 01 most system failures before leaving the local
office. By running diagnostic tests using telephone dialup
fa cilities, the Field Service eng ineer can give the customer
better service, because It Is easier to select which spares
and test equipment should be taken on the call. Certain
tests can be run during general timesharing . Even If the
main CPU Is inoperative, the console front-end processor
can access all buses and major registers.

The user can request a memory conllguratlon listing that
IndIcates which memory controller is online, what the
highest memory address conligured is, and how the memory is Interleaved .
All normal console capabilities, such as the ability to examine registers, change registers, start, stop, reset, and
load, are provided by the console front-end processor. An
operator command language is provided with the system.
Command Terminal Function.
The console front-end processor serves as an Intelligent
data link and buffer lor the Interactive terminals, relieving
the central processor 01 this overhead. The console frontend processor buffers the characters received and interrupts the central processor, either upon receipt of a clock
~nal or In the event it has a group of characters to send.
The central processor also sends groups of characters for
terminal output to the console Iront-end processor, further
enhancing effiCiency. Programmable terminal speed-set-

Total system security Is maintained because the onslte
system operator must activate the communications link.
Only the onslte personnel know the specific password to
the system each time remote diagnosis Is employed. Time
limits for system access can also be Imposed , and the
remote link cannot operate at a privilege level higher than
that specified by the local console terminal. All 110 to the
diagnostic link Is copied to the local term inal , giving onslle
personnel a record of all steps taken.

4-7

5
KL10-E
Processor

The Kl 10 central processing unit is the heart of DIGITAL's large-scale
computer systems. It provides the basis for the popular and successful
DECsystem-10 and DECSYSTEM-20 computer families.
The Kl 10-E version of the Kl10 is the central processing unit of the
DECSYSTEM-2040 and the DECSYSTEM-2060.
Important features of the Kl 10-E central processing unit are:
• 36-blt word length for programming efficiency and data resolution
• 398 logically grouped, microprogrammed instructions Including byte
and strIng manipulation, double-precision fixed and floating poInt,
and character editing and conversion
• Full 256K, 36-bit word memory space addressing without Indirect or
base addreSSing
• An architecture that allows modular expansion without component
replacement or complex reconfJguration
• An integrated PDP-11 front-end processor for diagnostic functions,
console functions, and handling of low-speed peripheral devices
• Extensive error-detecting circuitry for maintainability and availability
• Integrated high-speed data channels/controllers for disks and tapes
for improved reliability and price/performance
• State-Of-the-art memory management hardware for virtual memory
operation
• Four-word fetch capability for Increased bandwidth and performance
• High-speed cache memory with state-Of-the-art design; typlcallnllne
programming results in a 90 percent cache "hit" rate for efficiency
and high performance
• One of the most flexible priority interrupt systems available
• A full line of high-efficiency, high-performance UNIBUS and
MASS BUS peripheral devices to meet individual user needs
• High-speed Eel logic implementation
• Eight sets of general purpose registers that can be used as
accumulators, Index registers, or the first 16 locations of main
memory, having an access time of 125 nanoseconds

The Internal erchltecture of the Kl10-E centrat processing
unit can be considered a collection of special purpose
processors connected through high-speed internal buses.
Four major subsystems constitute the centrel processor
for this discussion:
• The Execution Box (EBox) and associated buses that
execute machine Instructions and provide control for
other subsystems
• The main memory subsystem that consists 01 a memory
control unit (MBox), associated buses, and internal MOS
memory
• The front-end diagnostic and console PDP-11 subsystem that also supports UNIBUS unit-record equipment
• The I/ O subsystem that consists of Integrated channels/ controilers and PDP-II-based communications
subsystems

eXECUTION BOX (EBOX)
The execution box (EBox) Is the part of the processor that
actually executes Instructions and performs various control functions for overall CPU operation. The Kll0-E has
398 microprogrammed Instructions. Each Instruction Is
implemented as a series of microinstructions that performs various logical functions such as processor state
control, data path control , and the actual Implementation
of each instruction. Using microcode as opposed to
"hardwired" instruction Implementation , a machine Instruction executes one or more m lcrostore instructions. To
execute a given machine instruction, the mIcroinstruction
sequence associated with that instruction performs functions such as the data movement, operations on data, or
control steps needed to execute that Instruction. The m icroprogrammed Kll0-E central processor oHers several
Important features:

Figure 5-1 lIIustrates a fully conligured Kll0-E central
processing unit. Key elements of this Implementation of
the processor are internal memory, a MASS BUS for hlghspeed disks and tapes, and a UNIBUS for low-speed peripherals (unit record and PDP-II-based communications
Interfaces). The MASSBUS terminates In RH20 integrated
channels/ controllers, and the UNIBUS terminates In the
DTE Interface.

• The CPU executes TOPS-20 paging (memory management) and monitor call Interface
• Eng i neering changes or central processor
improvements can often be Implemented by microcode
changes, rather than by wiring changes, since the microcode Is loaded by the PDP-II front-end processor
during system start-up
• Cache and virtual memory operations are enhanced
• The packaging technology of microcoded hardware permits smaller size and greater flexibility In Instructions

Figure 5-2 Illustrates the SO-inch-high DIGITAL Corporate
"High-Boy" cabinets in which the KllO-E is paCkaged .

r------------ - -----~--------------- - - - ------ - ------ --- -- ,

,,
,,
'-- ,-;'

11140

0
T

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Eel
PFlOCESSOR

UP
TO

•

I+-+ !.

CACHEAN O
MEMORY CONTROL

d i

,,
l
,
~---- -- ------,
~
,,, ,----,
0
~~:-+~ "'-n
,,, I 1.-- ----.., A A
UP
TO
,, •
2
2
•
0
0
,,
,, "
I """ I
,,,
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--- ---------- -'-- · ----- --- . . --- ---- ClY

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CHANNelS

c ••

KU NtK
UNIBUS

------------,

PenpherlilS

r---

Mulliplexed

MASSBU S

110 Bu.

Peript8-als

Opbonet

Figure 5-1
Kl10-E Central Proce .. lng Unit

5·1

_ _ _ _ _ _ _ .J

INTERNAl
MEMO RY

In add ition to the 398 Instructions, the KL 10-E provides 64
programmable operators, of which 33 trap to the monitor
and 31 trap to the user's call area. The remaining instruction codes are unimplemented and reserved lor future expansion. An attempt to execute one of the unimplemented
instructions results In a trap to the monitor.

"''''" 2 7

./I

=
FRO NT-

END

SOBSYSTEM

OTE
/
O<B
RH20
=
,==,

FRONTEND

c:~i'~...

0l/.

~:,

,,,
,,

,,,
,
, ,

,
,,,

Despite Its size, the Instruction set is easy to learn. It is
logically grouped Inlo families of instructions, and Ihe
mnemonic codes are constructed modularly. All instructions are capable of directly addressing 256K 36-bltwords
of memory without resorting 10 base registers, displacement addressing, or Indirect addressing. Instructions can,
however, use Indirect addressing with Indexing to any level. Most lnslruCllon classes, including floaUng point, allow
immediate mode dala, the result of which is effeclive ad·
dress calculation used directly as an operand to save
storage and speed execution .

ECl
PROCESSO R

ImJNAL
MEMORY

Secj" l

The procassor mods concept has been a keys lone in
DIGITAL's timesharing or muilitasking systems for more
than a decade, and it Is central to the KL 10-E Implementation. Instructions are executed In either ussr mods or execulivs mods. In a multltask environment a user must nOI
execute Instructions that would jeopardize other users.
With the KL 10-E, attempted execution of such an Instruction In user mode will trap to the operating system analyzIng the Instruction. and appropriate action will be taken.

Figure 5-2
KL10-E Mechanical Conflgural/on

• Architectural extensions can often be made using microprogramming, obviating the need lor extensive engineerIng change orders (as, for example, In the support
of new peripheral subsystems)

In executive mode operation any Implemented instruction
Is legal. The monitor operating In executive mode Is abls lo
control all system resources and the state 01 the processor. Executive and user modes are each further divided
Into two submodes. Table 1 defines the processor moda
Implementation.

The microcode Is actually Implemented with 2,048 75-bit
words. The EBox also has a 512-word Instruction dispatch
table that rapidly decodes InstrUClions and dispatches
operations to the appropriate microstore sequence to implement the instruction.

Table 1

Besides performing the basic functions 01 decodIng and
implementing control store steps for the Implementation of
each instruction In the KL10-E set, the microcontroller executes the more fundamental operations 01 sequencing
the program and processing Interrupts. The KL 10-E set
also handles TOPS-20 paging operations beyond the basic address translation made, lor example, by the pager.

User Mode
Public Submode
• User programs
• 256K word address
• All instructions permitted unless they compromise integrity of the system or other users
• Transfers to concealed submode onty at entry points

The EBox also contains eight sets of 16 general purpose
registers, four timing and accounting meters, and a OTE
interface to the low-speed UNIBUS 110 devices. The Interface to the low-speed control devices Is controlled by the
EBox's microcode. It performs the required deta and
control transfers by stealing microcode cycles between the
execution 01 CPU instructions.

Concealed Submode
• Proprietary programs
• Can READ, WRITE, EXECUTE, or TRANSFER to any
location labelled public

In.tructlon Set
The KL 10-E has 398 microprogrammed Instructions, an
extremely large repertoire. This provides the flexibility required for specialized computing problems. Since the set
provides a very wide selection of instructions from which
to choose, few are typically needed to perform a given
function. Programs can therefore be shorter than they
would be on other computers. The large instruction set
also simplifies the monitor (operallng system), language
processors, and utility programs.

Executive Mode
(monitor)
Supervisor Submode
• General management of system
• Those functions that affect only one user at a time
• Executes In virtual address space labeled public
5-2

Procesaor Modes

Byte Manipulation - Five byte-manipulation instructions
pack or unpack bytes of any length anywhere within a
word .

Kernel Submode
• 110 for system
• Those functions that affect all users

Logic Instructions - logic Instructions shift, rotate. and
execute the 16 Boolean operations on two variables.

Instruction Format - In all but Input/output Instructions,
the nine hlgh·order bits (0 - 8) specify the operation. Bits 9
- 12 usually address an accumulator, but are sometimes
used for special control purposes such as addressing
flags. The rest of the instruction word always supplies In·
formation for calculating the effective address that Is used
for Immediate mode data. or that Is the actual address
used to fetch the operand or alter program flow. The effec·
tive address Is refarred to throughout this document as tha
user (or operating system) virtual address. Memory map·
ping and/or paging hardware can map this effective ad·
dress into a very different physical address within main
memory. However, the programmer need only be
concerned with an effective user address space that can
be 256K words. Bit 13 specifies the type of addressing
(direct or Indirect). Bits 14 - 17 specify an Index register for
use In address modification (zero indicates no indexing),
and the remaining eighteen bits (18 - 35) contain a memory address that Is used as the basis for effective address
calculation or as an actual operand In Immediate mode
format.

FIxed-Point Arithmetic - The Kl10-E is a 2's complement machine in which zero is represented by a word con·
talnlng aU zeros. As in comparable Implementations, the
Kl10-E logic does not keep track of a binary point. The
programmer must adopt a point convention and shih the
magnitude of the result to conform to the convention used.
Two common conventIons are to regard a number as an
Integer (binary point to the right) or as a proper fraction
(binary point to the leh). In these cases. the range of numbers represented by a single KL 10-E word Is -2" 10 2S1- 1
(binary point to the right) or - 1 to 1-2-u (binary point to
the left). Since multiplication and division use doublelength numbers, there are special Instructions with Integral
operands for these operations.
The format for double-length , fixed-point numbers Is an
extension 01 the single-length format. The magnitude (or
Its 2's complement) Is the 70·blt string In bits 1 - 35 of the
hlgh- and low-order words. Bit 0 of the high-order word Is
the sign; bit 0 of the low-order word Is Ignored. The range
for double-length integer and proper fracllons is thus _2 70
to 2- 70 -1 (binary point assumed at the right) or -1 to 127(1 (binary point assumed at the left). Zero is represented
by a word containing ali zeros.

All input/output Instructions are designated by "ones" In
bits 0 - 2. Bits 3 - 9 address the device to be used, and bits
10 - 12 specify the operation. Bits 13 - 35 are the same as
for noo·I/O Instructions. They are used in calculating an
effective address for the data to be transferred.

Floallng-Polnt Arithmetic - The KL 10-E processor has
instructions for scaling, negallng . adding, subtracting.
multiplying, and dividing In slngle- and double-precision
floating-pOint format.

Flgure 5·3 Illustrates the two Instruction formats lor the
Kl10· E.

'00'"'' ""
o

••".u,"'"
..
000<

1'
023

&11,2,31.,718

In single-precision floatIng-point format, one bit Is used for
the sign, eight bits for the exponent. and 27 bits for the
fraction. In double-precisIon floating-point format, one bit
is used for the sign, eight bits lor the exponent, and 62 bits
for the fraction. This results In a precision In the fraction of
1 part In 4.6 X 10" and an exponent of 21n the range from
-126to + 127.

'''''''
REGISTER
_ESS

REGISlEA
''''''''
_ESS
/
/1

MEMORY ADOAESS

1110121'141718

Normalized slngle·preclslon lIoating-polnt numbers have
a Iraction that can range In magnitude Irom 'n to 1-(2- 17).
Increasing the length of a number to two words does not
significantly change the range, but It does increase the
precision. In any format the magnitude range of the
normalized fraction Is from V. to 1 less the value of the
least significant bit. In all formats the exponent range Is
from 2- 1" to 2m .

Figure 5·3
Instruction Formats

Fixed/Floating Conver sion - Special instructions convert between fixed- and floating-point formats. Two sets of
conversion instructions are provided . one optImized lor
FORTRAN. the other for ALGOl.

Ha lt·Word Data Transmission - Half-word data
transmission Instructions move hall a word and can modify
the contents of the other half of the destination location.
The 16 sets of instructions differ In tha direction they move
the chosen hall-word and in the way they modify the other
hall of the destination location .

Arithmetic Testi ng - An arithmetic testing Instruction can
jump or skip depending upon the resu lt of an arithmetic
test. II can also perform an arithmetic operation on the
tested word.

Full·Word Data Transmission - Full-word data transmission Instructions move one or more lull words of data from
one place to another. The Instructions can perform minor
arithmetic operations such as calculating the negative or
the magnitude of the word being processed.

logica l Testing, Modification , and Ski p - These Instructions modify and/ or test using a mask , and/or skip on
selected bits In an accumulator.

5-3

Program Contlol - Program control Instructions Include
several types of jump Instructions and subroutine calls Including calls that save the return address on a pushdown
stack.
Input/Output Operations - Inpul/output (110) Instructions govern all direct transfers of status to and from the
peripheral equipment. They also perlorm many operations
within the processor. Block transfer Instructions handle
bulk data transfers to and from medium-speed 110 bus
devices. High-speed devices transfer data directly to
memory through Internal channels.
Unimplemented User Operations (UUOs) - Many of the
codes not assigned as specific Instructions are executed
as unimplemented user operations. The word given as an
Instruction Is trapped and must be Interpreted by a routine
Included lor th is purpose, either by the programmer or by
the monitor.
TOPS-20 uses the Instruction JSVS to transfer control
from the user program to the monitor where any of a large
number of functions Is performed. The function perlormed
is determ ined both by the effective address and by arguments in the user's registers.

break suspends a user program end traps to the opereting
system. This facUlty Is particularly useful In program development and debugging.
Meter.
Two meters built Into the KL10-E provide a number of
timing and counting functions, Including an interval timer
and a time base counter.
The meters are controlled by 110 Instructions to internal
devices. Many of the timing functions utilize a m icrosecond pulse source originating In the basic 30-megacycle
mach ine clock. Designed with a tolerance of 0.005 percent, this pulse source drifts less than five seconds over 2.
hours.
The Interval timer Is a programmable source of interrupts
with a one-microsecond resolution. Used lor realtime appUcatlons and for page management by the monitor. It can
Implement a realtime deadline schedule with varying
deadlines.
The ti me base Is a SO-bit, one-microsecond resolution
counter that can generate a source of elapsed time. This
SO-bit register provides more than 9,000 years maximum
time belore wrap-eround.

Buslnen Instruction Set _ There are live classes of Instructions In the Business Instruction Set of the KL10-E
central processor. Four of these are arithmetic instructions
to add, subtract, multiply, and divide using double-precision, fiXed-point operands. The STRING Instruction in the
filth ciass can perform nine separate string functions.

Priority Interrupt System
The KL 10-E has a powerful, flexible priority Interrupt system that permits overlapped concurrent asynchronous operation 01 the central processor, peripheral controllers end
devIces, and software service routines.

These functions include an edit capability, decimal-to-binary and blnary-to-declmal conversion in both offset and
translated mode, move-string in both oifsetand translated
mode, and compare-string In both offset and translated
mode. Offset mode Is byte modification by add ition of the
effective address of the string Instruction . Besides
providing the translation function, these instructions can
control AC flags and can detect special characters In the
source string .

Devices are assigned under program control to anyone of
seven priority levels through dynamic loading of a 3-blt
register within the device. Each of the seven levels has any
number of programmable sublevels with which a programmer can change the priority level of any device, or
disconnect the device from the system and later reinstate
It at the same or any other level . In a similar manner, a
program can set, enable, or dlsabla all (or any combination of) levels wIth a Single InstructIon. The program can
assign some or all devices to the same level.

The Business Instruction Set provides faster processing
because there are special instructions for a variety of
string operations. These instrucllons can be used on many
code types such as ASCII and EBCDIC. The Business Instruction Set exemplifies a microprogrammed processor's
advantages In meeting special user needs.

The system can also generste Interrupts through software.
so hardware can operate on a high-priority level while
related computations can be performed on a lower level.
The program-assignable priority Interrupt system provides much greater flexibility than permanently hardwired
systems because hardwired systems require a large number 01 levels, often Operate with an extremely high overhead , and cannot change devIce priorities wIthout system
shutdown and rewiring.

Trap Handling _ The execution 01 programmed trap instructions permits the KL 10-E to directly handle arithmetic
overflows and underllows and pushdown list overllows.
Fast Register Blocks - The KL 100E architecture Includes
eight sets of 16 general purpose registers. They can be
used as accumulators, Index registers, or as the IIrst 16
locations in maln memory. Since register addressing is
included in the basic instruction format, no speciallnstructlons are needed to access these registers. Different raglster blocks are used for the operating system and individual
users, eliminating the need for storing register contents
when switching from user mode to executive mode.

In conjunction wIth the priority Interrupt system, a set of
Instructions (BLOCK-IN/ BLOCK-OUT) allows the transfer
of blocks 01 information between a device and memory In
a single operation. When an Interrupt occurs, the KL 10-E
will trap to a predetermined location . The BLOCK IN/ BLOCK-OUT Instruction Identifies the source of the Interrupt, translers a word In or out, updates word count and
data address, and dismisses the Interrupt. When the word
count Is zero, a different action occurs that allows the program to either prOCess the block of Information that has
been transferred or to move on to other sct/vltles.

Programmable Address Break _ When s specified
location Is properly referenced, e programmable address

5-4

MEMORY SUBSYSTEM
Central to the KL 1O-E architecture Is the Implementation of
all memory control through a discrete memory controller
(MBox). The MBox Is responsible lor all memory requests
from the E80x and Integrated channels/controllers for
high-speed peripherals (disks and tapes). The MBox does
paging (address translation) for memory management and
contains the cache memory for CPU models so equipped.

MOS Memory
Metal Oxide Semiconductor (MOS) memory has a word
length of 44 bits (36 data bits, seven error detection and
correction bits, and one spare bit). This Implementation
allows hardware detection and correction of a single-bit
data error and hardware detection of a double-bit error.
MOS memory Is available In 256K word Increments to a
maximum of 2M words.

Internal Memory
The Internat memory Implementation of the KL 1O-E offers
Improved reUabliity and lower cost per word than external
memories, due to Its simplified design and, since no long
bus Interfaces are required, fewer components.

If a correctable (single-bit) error Is detected, the hardware

Table 5-2

automatically corrects the data word , and notifies the CPU
with a flag . This allows the program to continue without
consideration of such memory deterioration while, at the
same time, the operating system can gather statistics concerning possible failing areas of memory. II a detectable
but noncorrectable (double-bit) error Is encountered, the
memory controller signals the CPU, sets a noncorrectableerror lIag, and provides certain other data on the first error
detected . The operating system will mark the page containing this location and will not reuse It.

Internal Memory System

Featu re

MF20 Memory System
M F20 (M OS)

Word Size

36 bits plus 7 errorcorrecting bits

Minimum Memory Slze-

256K words

Maximum Memory Size·

2,048K words

Read Access Time"

467 ns

Read Cycle Time"
I-word
4-word

667ns
1,287 ns

The spare bit can be substituted (upon software command) for falling bits, significantly enhancing the mean
time between failure (MTBF) for this type memory.
Cache Memory
Cache memory decreases Instruction execution time by
substantially speed ing the average memory reference.
This is accomplished by placing a high-speed semiconductor memory (the cache) Inside the MBox. The cache
can hold up to 2K words from memory. Whenever the
program accesses a word held In cache, the request Is
satislled In 133 nanoseconds, compared to 867 nanoseconds or more for a memory reference as measured at
the EBox.

Interleaving
Minimum memory unit
that can be disabled

The success of cache memory depends on the quality of
the algorithm used to decide which 2K words from memory are cached . Cached locations change constantly wlth
varying system demands, but the algorithm is based on
the assumption that memory references tend to be somewhat localized . In a typical program the flow of control Is
linear within a narrow scope. If an Instruction has Just been
executed from location N, there Is a high probabil ity that
there will soon be an instruction executed from location N

• Within CPU cabinet
• • Measured at memory

,,
,,,

""..."

Section 2

INTERNAL

+ 1.

MEMORY

The "hit rate" of the KL 10- E cache memory usually
exceeds 90 percent.

Figure 5-4
Internal Memory Systems Configuration

Several unique design features of the KL 10-E cache memoryare:
• KL 10-E cache Is not a write-through cache. If the EBox
Instructs the MBox to write a given location, the location
Is modified only In cache. The corresponding physical
location will be updated only when the monitor Instructs
the MBox to sweep cache or when a quadword (lour
adjacent 36-bit words) must be emptied to make room
for new data .
• The cache Is organized to handle physIcal addresses.
Cache as used on some other large systems, however, Is
oriented toward vlr1uai addresses. Stanford University
developed the cache algorithm used in the Kl10-E, and
Its modeling demonstrates that us ing physical addresses is more efficient than using virtual addresses.

15 _

MEMO RY CONTROL
(M ·SOJ()

e
A
e

execUTE

BOX
(E·SoJ()

5-5

• The hardware's use of the cache Is dependent upon the
M 80x microcode that Is normally set up to support all
four cache pages. However, If desired, some or all 01 the
cache can be turned off. This option Is exercised when
the front end Is Initializing the Kll0-E at system startup.

. . - .. Data WOrds

Organ ization
The cache can hold up to 2,048 words from memory. It Is
organized as four separale, 512-word pages that operate
In parallel.
Each cache page has a directory associated with II. The
directory consists of 128 13-blt entries. A single directory
entry contains information concerning four words of data
within the cache page (Figure 5-6).

A four-word cell described by a single directory entry Is
called a quadword. The 13-bit directory entry for a quadword contains the physical page number of the page In
memory that originated the quadword. In turn, the position
of a word within a cache page Is always the same as the
position 01 the word In Its original page of memory.
In the following simplified example, assume that there is
only one page 01 cache and lis associated directory, rather
than the four thai are actually provided In the hardware.
Suppose that the EBox has requested the contents of the
22-blt physical address 14707002 (addresses are in octal
nolatlon). The MBox must determine If It must read memory location 14707002, or If that location is already in cache.
The IIrst step Is to split the physical address Into a 13-bll
physical page number, in this case 14707, and a 9-bit
index Into the page 002. In other words, the search Is concerned with the oo2nd word 01 physical page 14707.11 this
word Is already cached, the only place It could be In a
single cache page would be word 002, because the position 01 a word within a cache page is always the same as
the position of the word In its original page. The MBox
must examine the 13-bit directory entry corresponding to
the 002nd word 01 the page and compare It to the desired
physical page number of 14707. If the directory entry holds
14707, then the 002nd cache page word Is Indeed the required word . If the comparison lails, then It must read
physical memory.

13-8i1 DIrectory

Figure 5--5
Cache Page Structure

The above example was simplified by the omission of
three-fourths of the cache pages. In a real system with lour
pages (2K words) of cache, a given physical word might
actually reside in anyone of the four pages 01 cache. It has
to be In word 002 of whichever page hotds It; Just as It had
to be In word 002 of the single cache page. The MBox
compares the desired physical page number of 14707 to
the contents of four directory entries, one for word 002 In
each of the four cache pages. "a match Is found, then the
data Is taken from the proper page. Otherwise physical
memory must be read.

Since there is exactly one directory entry lor each quadword , it follows that all four words In the quadword must
come from the same physical page. Moreover, a word
must have the same position In the cache page that It had
In the physical memory page. These facts Imply that the
four words In a single quadword are physically contiguous
In memory as well as in cache - a key concept In the
Kll O-E cache design.

The algorithm that determines the order In which the
cache pages are filled uses tables In RAM storage. Therefore, by rewriting the tables It Is possible, under program
control, to shut down part or aU of the cache.

'Valid Bit
Written Bit

xxxxxxxxxxxxxxxx

•

xxxxxxxxxxxxxxxx

Figure 5-6
Single Entry in Cache

5-6

•

entry exists, the contents 01 the entry supply the 13-bIt
most Significant part of the physical memory address and
also supply three bits that Indicate types of memory references allowed to this page. If the memory request is consistent with the request type allowed, the physical address
used consists of the 13 bits from the related page table
entry as the most significant bits of the physical address,
and the nine least significant bits 01 the effective address
as the least Significant bits of the physical address.

Syslem Conlrol 01 Cache
There are Ihree different operations to which the monllor
can subjecllhe cache: Invalldallon, validation, and unloading. These operalions can be performed on the entire
cache or on entries belonging 10 a single memory page.
To invalldale a locallon means 10 clear Its valid and written
bits, Ihus emptying the location. Validation of a location
means Ihal, II an entry has been written since It was
brought In from memory, Ihen the modified contents must
be written back into physical memory, This is necessary
because the cache Is not a write-through cache. The unloading 01 a location requires Ihe MBox to validate the
location and then to invalidate It.

When the relocation data lor a referenced page does not
exist In the hardware page table, Ihe microcode reads the
relocation data from the page table In memory, stores It In
the hardware page table of the KL IO-E, and proceeds.
The operating system assigns the memory area for each
user by loading the various In-memory page tables, setting
up the trap locations In the user page map, and responding appropriately when a trap occurs. The monitor provides memory protection for itself and for each user by
filling the page tables only with entries that are allowed to
be accessed. This makes It Impossible for a user to
infringe on another user's physical memory area.

Memory Mapping on the KL1O·E
The KL 10-E provides a hardware Implementation 01 memory address mapping from a program's memory address
space (effective address or virtual address) to the physical
memory address space. During mapping, the most significant bits of the memory address are changed dynamically
to indicate the physical address at wh ich the program Is
running , Mapping provides access to the entire physical
memory space, which can be up to 16 times larger than the
maxJmum user address space, The user's eflectlve address space i s 256K words addressed with IS-bit
addresses. The physical address space Is 4M words addressed with 22-bit addresses (where 4M Is equivalent to
4,194,304 decimal). Provisions exist In the KL 1O· E to allow
a user address space larger than 256K words.

The major benefits 01 this paging capability are:
• Full memory prot action alone user from another
through hardware and microcode
• Freedom to scatter the pages 01 a user virtual memory
area throughout physical memory (programs do not
have to be physically contiguous), eliminating memory
shulliing and complex memory management even
though a user program grows during execution
• The opportunity to execute a program when all 01 Its
pages are not In physical memory (i.e. , a virtual memory
capability)

The memory mapping process uses the nine most significant bits 01 the virtual address as an Index Into the
appropriate user or executive page map. The data located
by the Index provides 13 bits that are appended to the nine
least significant bits 01 the virtual address to lorm the 22bit physical address. Also provided are three bits that Indicate what type of memory requests are allowed to the page
in question, tor example, none, read-only, or proprietary.
Figure 5·7 1I1ustrates this mapping by means of the page
table.

FRONT·END SUBSYSTEM
A key element in the operation and maintenance of the
KL 10-E is the POP-II-based console/diagnostic Iront-end
computer. This minicomputer provides all console func tions lor the KL 10-E and Its associated operating systems
(TOPS-IO and TOPS-20).

effECTIVE AOOAESS

,
~{

The POP-It interfaces to the KL I O-E through a dedicated
DIGITAL Ten-to-Eleven (OTE-20) Interface with a tull-capabillty UNIBUS. The OTE·20, under control of both the
KL 10·E and the Iront-end PDP-II, can examine or deposit
words Into memory, and can provide two-way data transfers. Asynchronous communications lines for the console
term inal and a dedicated line for remotellocal diagnostic
functions (KLINIK) connect the user to the operating system through the console Iront end.

""'WOODS
I IB11T5 - { !il2PMlES

,...." ,

PAGE

~
"

In addition to the OTE·20 link, both the KlIO-E (through an
AH20) and the POP-II (through an RH11) are Interfaced to
separate ports on an AP06 disk drive. Figure 5·S Illustrates
these connections.

.0II6K WOROS

I 2281TS - { el92PAGES

Figure 5·7
Memory Mapping

In addition to the console and diagnostic functions, the
KL10-E's Iront-end console/diagnostic PDP-11 supports
unit record and asynchronous communications
equipment. From the user standpoint, these devices operate Identically to those Interfaced to separate PDP-lis.
They are explained In detail in the section below on 110
devices.

II the address is In the range 0 - 17., Inclusive, the hardware fast regIster blocks are referenced Instead of the
main memory system. The user mode bit and the nine
high ·order bits of the virtual address are used to perform a
"table lookup" In the hardware page table. If a page lable

5-7

u"sus

I
I'OI'-n

C"'_
PROCESSOR

POP-II

"'"0'''

flOPPY

RHn

OR
"""
DEC'''''

OI.n

UN'

""""".

CAAO

READER·

L-

CO""'''

DUAL .poRTED

"".

TERMINAL

LOCAL OR REMOTE
I<UNIK TERMINAL

-Kl.IO-E

Figure 5-1
Front-End Subsystem
formatted specifically for the front-end Illes. There ara
both hardware and software interlocks to prevent the
KL10-E and PDP- l1 lrom interfering with one another. The
PDP-II disk area Is not available for user storage.

All KL 10-based systems rely on the front-end for at least
two basic functions. First. the PDP-11 Is used to initiate
CPU operations from 8 dead stop. This process Involves
setting up Kll0-E status. loading mIcrocode , configuring
memory, and starting the monitor bootstrap. These operations are conducted primarily across a dIagnostic bus that
connects the front-end to both the EBox and the MBox by
software. Second , the PDP-11 supports the console terminal with which an operator can control the system. It Is this
term inal that governs the operatIng system and th,J tasks
running under It. The terminal can also be used as a normal user terminal.

KL 10-E systems can support up to four PDP-lis; however,
only one of these can be the controlling front end. To prevent conflicts between different PDP-I I s, the operations
descr i bed In th is section can be accomplished only
through a "privileged" hardware- and software-selectable
DTE-20.
INPUT/OUTPUT SUBSYSTEM
The KL 10-E inpuVoutput subsystem provides standar d Interfaces and control logic for connecting the KL 100E to a
wide range of peripheral and communications equipment.
This includes disks and magnetic tapes, and - through
PDP-II-based communications subsystems - cardreaders, tlneprlnters, synchronous, and asynchronous lines.
Details of the operation and the specifications of these
peripheral devices are described In Section 7.

These functions are implemented us ing a spec ial
operating system that runs in the front-end with supporting code for TOPS-20.
The PDP-l1-based operating system Is built around
DIGITAL's RSX realtime system software. RSX allows concurrent operation
multiple tasks. One task Is the "command parser," the program that recognizes commands
typed on the console terminal and passes appropriate
messages through the DTE-20 to the TOPS-20 operating
system. Other tasks Include KLiNIT, which oversees initialization of the KL10-E processor, and KLiNIK, which
provides a diagnostic environment lor diagnosis and control of the KL10-E by privileged users from either local or
remote locations.

To standardize the interface and permit the connectIon of
a wide range of peripheral devIces, DIGITAL has long used
a " bus" architecture. Three external buses (see Figure 5-9)
are available to communicate with the Kll0-E CPU:
• Multiplexed 1/ 0 bus
• MASSBUS
• UNIBUS

Some devices associated with this front end support console and diagnostic operations and can be used as peripheral devices. These Include the RHII disk controller
and a floppy-d isk drive. The floppy-d isk drive can be used
as an alternate bootstrap device If, for some reason, the
RP06 disk either cannot be used or contains Incorrect information.

Multiplexed 1/0 Bus
A multiplexed 1/ 0 bus Is optional on the Kl10-E. TOPS-20
supports un it record and communications capability
through PDP-I I-based controllers but does support a lew
special devices on the 1/ 0 bus. See Section 7 'or Information about these peripheral devices. The 110 bus provides
control and a character-by-character, Interrupt-driven interface lor low-speed devices. Figure 5-10 illustrates the
hardware asSOCiated with the KL10-E 1/0 bus.

Front-end operations require that the dual-ported RPOS be
available for normal operations. The RP06 Is connected to
both the KL1O-E and the PDP-11 through dual-ported
hardware. The disk used Is KL 1O-formatted with a section
5·8

•

memory controller and Individual MASSBUS devices. Up
to eight RH20s can be Installed In the Kll0. For each davice, the channel provides 8 15-word data buffer, a
channel command word register, and a control command
word pointer that serves as a program counter. The channels transfer data Independently of the KL 10-E execution
logic by executing channel programs placed in memory by
device service routines that use memory cycles. The device service routines are in the operating system.
A channel bus Interfaces the RH20 Integrated controllers
to the memory control unit (MBox) of the KL 10-E CPU. The
bus Is a physically short, high-speed data transfer path
designed for peak 1/0 bandwidth of six million words per
second - well in excess of that encountered in any existIng memory or peripheral units - between the memory
control unit and the MASS BUS controllers (RH20S). Operating In synchronous time-division multiplexed mode, the
channel bus allows the connectfon 01 multiple RH20s In
memory.

Each RH20 terminates In a MASSBUS. This high-speed
data path connects the RH20 integrated controllers and
mass storage devices such as disk or tape. Operating
either asynchronously or synchronously, the MASSBUS
transfers control and status Information or blocks of data
between devices and controllers.

Figure 5-9
KL 10·E Input/Output Bus Architecture

DIGITAL disks and tapes connect directly to the MASSBUS , providing an Integrated, high-speed subsystem for
mass storage.

MASSBUS
DIGITAL's MASSBUS allows connection of a wide range of
DIGITAL disks and magnetic tapes to the KL1O- E central
processor. See Sectlon 7 for Information about MASSBUS
peripheral devices. Each MASSBUS can Interface as many
as eight peripheral device controllers to a single RH20
MASSBUS controller. Each RH20 Interiaces to the ESox
through the EBus and to one of eight data channels located In the MBax through the channel bus (CB us). (See Flg-

UNIBUS
DIGITAL 's UNIBUS prov ides the third path between
external devices and the KL10-E CPU. As Illustrated in
Figure 5-12, this interface uses the DTE-20 Interface to
provide:
• The ability to examine or deposit words In PDP-l1 memory and specified areas 01 KL 10-E memory (under the
control of a PDP-11 processor connected to the DTE-20terminated UNIBUS or the KL 10-E CPU)
• High-speed simultaneous transfer of data between PDP11 and KL10-E memory. This transfer operates In a

ure5-1'.)
The channel also Includes 8 series 01 multiple-word channel buffers to support high-speed 110 between the KL 10-E

MULTIPLEXED I/O SUS
DIA/S·

E-Box

HARDCOPY
CONTROL

Kl10

CARD
READER

LINE
PRINTER

CENTRAL

PROCESSOR

Figure 5-10
Multiplexed 1/0 Bus Architecture

5-9

DECTAPE

CARD
PUNCH

There are two ways in which the DTE·20 allows a PDP-II
to communicate with KL10-E memory. First, the PDP.l1
can use an examine/deposit feature that permits the PDP11 to read or write a single KL 10-E word. Second, DTE-20
transfers a string of data 10 or from Kll0·E memory. It Is
Important to note Ihat the PDP-II memory Is itself a UNI.
BUS device, and the DTE-20 can directly access it. For
Kll0-E accesses, the DTE-20 Interfaces to the EBox of the
Kll0-E processor. The DTE·20 does not operate unless a
PDP-II Is connected to it and the appropriate program Is
running In the PDP-11 .
The PDP·l1 can examine or make deposits to any address
within two windows defined in KL 10-E memory. The
windows are specified by the operating system exec process table and are known as the "to-lO" area and the "to11 " area. The PDP· 11 can write only to the "to· 10" area;
the Kll0·E can write to both.

Figure 5·"
MASSBUS Interface

on f-----.~~--__,-

A restricted DTE·20 cannot examine or deposit outside of
the windows established by the operating system. This enables the Kll0·E to protect Itself from a malfunctioning
PDP-II . However. for diagnostic functions, a privileged
fronl end used only as the consolelfront-end processor
can examine and deposit anywhere In Kll0-E memory.
The other transfer mechanism, byte Iransfer, permits
transfers to or from anywhere In KL 10-E memory. Byte
size can be eight or 16 blls al the program'S option, and
byte transfer supports concurrent ''10-10'' and "to-11 "
transfers.

Figure 5·12
UNIBUS Interface

PDP·11 "byte" mode and transfers 8· or 16·blt bytes
under the control of either the PDP·11 or KL10-E proc.
essors.
• Doorbell Interrupts - the PoP·l1 can cause an Interruptto the KL IO·E processor and vice versa
The oTE-20's two operating modes, restricted and prlvi.
leged , are controlled by a hardware switch on the oTE.20.
The privileged oTE·20 Is used only for the console/frontend PDP-II ; it Is discussed In the section on Front-End
Subsystems in this document. Only the restricted oTE-20,
used to control peripheral devices and communications
equipment, is described here.

Once a transfer has been initiated, the DTE-2Q handles It
without further Intervention from either CPU at the pro.
gram leveL The operating system will not be Interrupted
until the entire transfer Is complete. The DTE·20 recognizes the end of the transfer by the expiration of a byte
counter. Transfer completion results in an Interrupt on the
assigned PI leveL On the Kll0· E side, actuallmplementation of a byte or word transfer is by microcode. Thus, duro
ing transfers through the DTE. 20, cycles stolen from the
microcode Incur some CPU overhead.
As Indicated earlier. DTE·20 operation requires a PDP-II
processor. While service routines are Integral to the oper.
ating system, It is the PDP·l1 program that actually con.
trois the peripheral equipment. Cardreaders and lineprinters are supported on the consolelfront-end processor , as are a limited number of asynchronous
communications lines.
You can obtain additlonal'nformalJon on any peripheral or
communications subsystem by contacting your DIGiTAL
representative.

5-10

6
KS10
Processor

• •

The KS10 central processing unit (CPU) forms the basis of the
DECSYSTEM-2020.
The KS 10 has changed mainframe computing. People constrained by
budgets to settle for something less than a mainframe can now install a
KS10-based OECSYSTEM·2020 with full assurance that softwarecompatible growth Is easy, cost-eHective, and straightforward.
The DECSYSTEM-2020 comprises a number of major units or
subsystems that communicate with each other. The minimum system
has five subsystems: processor, MOS memory, console. a UNIBUS
adapter to handle the disk system, and a UNIBUS adapter to handle all
other peripheral devices.
The console, which is based on a microprocessor, boots the system
from disk and handles Interaction of the operator or a remote
diagnostic link with other subsystems.

SYSTEM ARCHITECTURE
The KS10 microprogrammed central processor form s the
basis for the DECSYST EM- 2020 computer system. The
OECSYSTEM-2020 consists of four major subsystems:
• KS 10 CPU and memory
• Console and diagnostic microprocessor

• UNIBUS Adapters
• PMipherai controllers
KS10Technoiogy
The KS1Q uses low-power Schottky TTL and features a
four-bit data path slice microprocessor to provide full
TOPS-20 functionality at low cost.
Microprogramming technology used In the KS10 design
relies heavily on experience gained In the design and im-

plementation of the successful Kl 10 central processor
and several of DIGITAL's smalier central processors. MIcrocoded machine Instructions are Implemented by one or
more mlcrostote instructions that move or operate on data
or that control steps necessary to achieve the desired ef·
fecI.

Microprogramming Implementation of the KS10 central
processor provides several Important advantages:
• Engineering changes or central processor Improve·
ments can often be microstore (fIrmware) changes rath·
er than wiring changes
• The packaging technology of microcoded hardware ra-duces machine size and Increases flexlblllty of machine
instructions
• Microprogramming speeds virtual address cache and
virtual memory control operations

Figure &.1
Sy.tem ArchItecture
The heart of the KS10 Is an internal synchronous back·
plane bus, called the KS10 bus. A multiplexed, two-cycle
bus, It provides a control and data path between the processor, memory, console, and per i pheral devices .
Command and address Information Is transmitted from
one bus device to another during the first ISO-nanosecond
bus cycle. Data Is then transferred between the devices
during the following bus cycle.

The microprogramming Instruction combines with the
four·blt·slice technology to make the KS10 reliable, low·
cost, flexible, and compact. Chip technology has pro·
grassed to the poInt where a single chip contains an entire
data path, Including data registers, data operations, and
lestlng and control functions for four bits. Thus, to Imple·
ment a 36·blt KS10 central processor, nine four·bit data
path slice chips are used, plus a tenth four·blt data path
slice chip for extra control bits. Control lines from each are
connected to the mlcrostore logic, so the microcode can
dictate function, control, and data flow throughout the sys·
tem.

The bus operates In a bus request/bus grant mode before any device can transfer Information, it must first
request and be granted the bus. There is a bus request
line and a corresponding grent line for each device. The
bus arbitrator on the console module monitors all requests, resolves priority, and , whenever the bus Is free.
grants the bus by asserting the grant line for the requesting device with the highest priority. The bus arbitrator can
handle up to eight devices.
Figure 8-1 Illustrates the connectIon of the KS10 central
processor, memory, UNIBUS Adapters, and console via
the KSIO bU8.

The KSI 0 Central Processing Unit
The KS10 central processing unit consists of four extend·
ad hex modules. They are:
• The Data Path Execullve (OPE) Module that contains
data path, registers, cache, PI system, and Dispatch
ROM (Read·Only Memory)
• The Data Path Memory (DPM) Module that contains bus
Interlace, processor status flags, paging, cache directo·
ry, and shift counter
• The Control RAM Address (CRA) Module that contains
next microcode address logic, microcode leading hard·
ware, and 2K x 36 bits of microcode
• The Control RAM Memory (CRM) Module that contains
2K x 60 bits of microcode.

The bus performs several major functions:
• Transfer data to and from MOS memory through the
memory controlier under control of the CPU , console, or
a UNIBUS Adapter.
• Transfer data to and from 110 device registers under
control of the CPU or console. Any device outside the
CPU Is considered an 110 device.
• Transmit priority interrupt requests generated by the
UNIBUS Adapters and, upon CPU request, provide device numbers and Interrupt vectors from the Interrupting
device to the CPU.
6-1

• Provide a continuous clock train used by all devices to
sequence log ic and to synchronize operation with the
rest of the system.
• Equip the console to reset the system, to perform dlag.
nostic functions, and to signal ac power failure to the
devices on the bus.

supplies Information for calculating the effective address.
The effective address can be used as an operand (immediate mode) or as the actual (virtual) address to fetch an
operand or alter program flow. Bit 13 specifies the type of
addreSSing (direct or Indirect); bits 14 - 17 specify an
index register used for address modification (zero indicates no Indexing). The remaining 18 bits contain a memo·
ry address.
Hair-Word OataTransmisslon - Half·word data transmission Instruc!lons move half a word and can modify the
contents 01 the other half 01 the destination location. The
16 sets 01 Instructions differ In the direction they move the
chosen half-word and in the way they modify the other half
of the destination location .

The KS10 bus data path Is 36 bits wide. Additionally, there
are two parity bits associated with the data lines, one for
data lines 0 - 17 and a second for data lines 18 - 35. Each
device checks for correct parity when It receives Informa·
tlon over the bus. If bad parity Is detected , the CPU clock Is
stopped.
Cliche Memory
Cache memory decreases Instruction execution time by
substantially speed ing the average memory reference.
Main memory access time Is 900 nanoseconds; cache access time Is 300 nanoseconds. The typical KS10 cache hit
rate of 80 percent gives an effective average memory ac·
cess time of 420 nanoseconds. The KS10's 512-word
cache memory Is located on the Data Path Executive
(DPE) Module.

Full-Word Data Transmission - Full-word data transmls·
sian instructions move one or more full words of data. The
Instructions can perform minor arithmetic operations, for
Instance, calculating the negative or the magnitude of the
word being processed .
Byte Manipulation - Five byte·manlpulatlon Instructions
pack or unpack bytes 01 any length anywhere within a
word .
Log ic Instruction s - LogiC Instructions shift, rotate, and
execute the 16 Boolean operations on two variables.

Genera l Registers
The general registers consist of eight accumulator (AC)
blocks of 16 words each, located on the OPE Module. The
eight sets 01 registers can be used as accumulators, Index
registers, or the first 16 locations In memory. How the
registers are used depends upon how they are addressed
in the Instruction word. Access time to general registers Is
300 nanoseconds.

Fixed-Point Arithmetic - The KS10 Is a 2's complement
machine In which zero Is represented by a word containing
all zeros. As In comparable Implementations, the KS-IO
logic does not keep track of a binary po int . The
programmer must adopt a point convention and shift the
magnitude 01 the result to conform to the convention used.
Two common conventions are to regard a number as an
integer (binary point to the right) or as a proper fraction
(binary point to the left). In these cases, the range of numbers represented by a single KS-IO word Is _2 u to 2u -1
(binary paint to the right) or -1 to 1-2·u (binary point to
the left). Since multiplication and division use doublelength numbers, there are special Instructions with Integral
operands for these operations.

Mlcrosto re
The microstore Is located on the Control RAM Address
and Control RAM Memory Modules. 2,048 96-blt words
are provided. The microcode and microstore are considered integral to the hardware and are not available lor
operating system or user program use.
Instruction Sel
The KS10 central processing unit features 396 microprogrammed Instructions. Each Instruction is a series of microinstructions that performs various logical functions
such as processor state control, data path control, and
actual implementation of each instruction in the KS 1O's
set Since the set provides so many Instructions, fewer
Instructions are typically required to perform a given lunc·
tion. The instructions are log ically classed and consistent
in mode, making their use straightforward.

The format for double-length, fixed-point numbers Is an
extension of the slngle·length format. The magnitude (or
Its 2's complement) is the 70-blt string In bits 1 - 35 01 the
high- and low-order words. Bit 0 of the hlgh·order word Is
the sign; bit 0 of the low-order word Is Ignored. The range
for double-length Integer and proper fractions Is thus - 2711
to 2-"_ 1 (binary point assumed at the right) or -1 to 12 70 (binary point assumed at the left). Zero Is represented
by a word containing all zeros.

All instructions are capable of directly addressing 256K
words without resorting to base registers, displacement
addressing, or Indirect addressing . Instructions can use
Indirect addressing with indexing to any level. Many Instruction classes, Including floating point, allow Immed iate
mode addressing where the result of the effective address
calculation Is used directly as an operand to save storage
and speed execution.

Floating-Point Arithmetic - The KS10-E processor has
instructions for scaling, negating, adding, subtracting,
multiplying , and dividing in single· and double·preclslon
floating·polnt format.
In single·preclslon floatlng·polnt format, one bit Is used for
the sign, eight bits for the exponent, and 27 bits for the
fraction. In double-precision floating·point format, one bit
is used for the sign, eight bits for the exponent, and 62 bits
for the fraction. This results In a precision In the fraction of
1 part In 4.6 x 10 1 • and an exponent of 21n the range from
-128to +127.

In all Instructions, the nine hlgh·order bits specify the operation . Bits 9 - 12 usually address an accumulator, but
are sometimes used for special control purposes such as
addreSSing lIags. The rest of the instruction word always

6-2

•
add, subtract, multiply, and divide, using double-preclslon,lixed-polnt operands.
The STRING instruction, the fifth class, performs nine separate string functions. These functions Include an edit
capability; decimal-to-binary and blnary-to-declmal conversion In both offset and translated mode; and move
string and compare string In both offset and translated
mode. Offset mode Is byte modification by addition of the
effective address 01 the string Instruction. Besides providing the translation function, these Instructions can control
AC lIags and can detect special characters In the source
string.
The Business Instruction Set provides faster processing
because there are speclallnstrucllons for a range 01 string
operations. These Instructions can be used on a variety of
code types, SUCh as ASCII and EBCDIC.
Trap Handling - The KS10 provides programmed trap
Instructions to directly handle arithmetic overflows and underllows, pUShdown list overflows, and page failures. This
trap capability avoids recourse to the program interrupt
system.
Normalized single-precision Ilealing-point numbers have
8 fraction that can range In magnitude from 'h to 1-(2-").
Increasing the length of 8 number to two words does not
slgnillcantly change the range, but It does increase the
precision. In any formal the magnitude range of the
normalized fraction Is from 'h to 1 less the value of the
least significant bit. In all lormals the exponent range Is
Irom 2- ' " to 2117.

Proces.or Modes
Instructions are executed In either Executive Mode or User
Mode, depending on the state of the mode bit. In Executive
Mode operations, all Implemented Instructions are legal.
The monitor operates in Executive Mode and is able to
control all system resources and the state of the processor. In User Mode certain Instructions, such as direct 110,
are illegal and cause a trap to the monitor. Users are required to Issue monitor calls for such system services.

FlxedlFloatlng Conver,lon - Special KS10 Instructions
convert fixed-point formals to or from Iloating-point for-

mats. Two sets of Instructions perform this function, one

MEMORY

set optimized lor FORTRAN and 8 second set optimized
for ALGOl.

The KS10 central processor supports a hierarchical
memory system consisting of fast register blocks, hlghspeed cache memory, main (MaS) memory. and mass
memory subsystems such as disks. The fast register
blocks, cache memory, and main (MaS) memory are
directly controlled by the KS10 hardware and firmware.
Accessing Is mlcrostore controlled. Disk memory access is
controlled by the operating system.

Arlthmellc Teltlng - The arithmetic testing instructions
can cause a program Jump, no jump, skip, or no skip,
depending on the result of an arithmetic test, and may first
operate arlthmeticelly on the test word .

Logical Testing, Modification , and Skip - A group 01
Instructions modify and /or test. using a mask. They cause
a program skip or no skip, depending upon the value of
selected bits in an accumulator.

Memory Address Mapping
The memory address hardware was developed in conjunction with the software so that memory management Is
totally transparent to the user. Physical memory Is divided
Into 512-word segments called pages. All addresses, both
mon itor and user, are translated from the program's virtual address space to the physical memory address space.
This facilitates protection of the monitor and efficient use
01 physical memory. For example, only a portion of the
monitor need be permanenlly resident In memory, resulting In more memory available to the user.

Program Control - Program control Instructions Include
several types of program jump Instructions and subroutine
control Instructions that jump as well as save or restore
information on a stack .
The KS10 Instruction set Includes a group of operation
codes that are used as monitor calls. When included in a
user program, these Instructions trap to the operating system, which examines the Instruction and takes the appropriate action. This monitor call Implementation Is fundamental to TOPS-20 operation because in a multitask
environment. the operating system must control certain
operations.

The high-order nine bits of an 18-blt virtual address constitute the virtual page number and are used to Index Into a
hardware page map. If the 13-blt physical page number is
found In the hardware page map, then the low-order nine
bits of the virtual address are appended to the 13-blt
physical page number to form the complete physical
memory address. If the entry In the hardware page map

Bu,lnes, In,tructlon Set - There are five classes of instructions in the Business Instruction Set of the KS10 central processor. Four of these are arithmetic Instructions to

6-3

does not exist, the memory processor gets the entry from
the Individual page map In memory, and updates the hard·
ware page map.

perature. The 128 rows of KS10 MOS memory are
automatically refreshed by the memory hardware, one row
every 15 microseconds.

There are separate page maps In memory for the monitor
and for each user. These maps contain storage address
pointers that Identity a page either In memory or on disk.
The system Interprets three types of address pointers.

AU Information stored in MOS memory Is lost if power Is
removed from the memory Circuitry.

The first, called a private pointer, contains a physical sto·
rage address. If this Is a memory address. the system
loads the hardware page table with the Information and
completes the requested reference. If It Is any other ad·
dress, the system Initiates a trap to the monitor for appropriate action.
The second, called a shared pointer, contains an Index
Inlo a system table at a fixed location. This system table Is
called the Shared Page Table (SPT) and contains the
physical storage address of the shared page. The table,
addressed through a hardware register, enables the soft·
ware memory management routines to maintain just one
pointer to a page, no matter how many processes are
sharing Ihe page.
The th ird, called an Indirect pointer, contains a page number and an SPT Index. The SPT Index Is used to pick up an
address of a page table. To obtain the physical storage
address, the page table Is Indexed by a page number
given In the Indirect pointer. The pointer allows one page
to be exactly equivalent to another page In a separate
address space.

MS10 memory
The MS10 is a single-port memory using MaS random
access memories (RAMs). II corrects single-bit errors and
detects double·blt errors. If the memory control logic detects a correctable error on a memory read cycle, the following occurs:
• If the error Is in one of the 36 data bits, the error bit and
the parity bit are automatically corrected
• If the error Is In one of the seven check bits, no correction Is required, an error flag Is raised, and the address
of the faJllng memory Is held in a register
• A flag Is raised Indlcatrng that the logic has corrected an
error
• The memory control logic saves a 2O-blt address (for a
read or read-pause-wrlte request) and tha ECC code for
the first error detected to allow software monitoring of
memory condition
The MS 10 memory Is highly reliable because:
• Single-bit error detection and correctIon and double-bit
error detection are implemented In the memory control
logic
• Power supply Is a hlgh·efficlency switching regulator lor
low internal power dissipation
• Storage array component layout facilitates airflow over
module
• Extensive airflow and temperature profile measurements have been taken
• Modules are "burned In" prior to Installation
• Faults are Isolated to board level
• Correctable read errors are automatically handled by
the hardware, so correct data Is always sent to the CPU
and notification of the corrected error Is provided

To aid the monitor In memory management, Information
pertaining to how long a page has been In memory and the
number of processes sharing it is also stored by the hard·
ware In the Core Status Table.
MOS Memory
The main memory subsystem of the KS10 central proces·
sor consists of metai oxide semiconductor (MOS) memory
connected to the KS10 bus by a memory controller. The
MS10 memory Is available In 64K word increments up to a
maximum of 512K words. The memory word length is 43
bits; 36 data bits and seven error-detection and correction
bits. Memory Interleaving Is not required.

CONSOLE SUBSYSTEM
The console Is an extremely Important subsystem In the
KS 10 central processor because it controls all consoie and
diagnostic functions. The console Is housed on a sIngle,
extended hex module and uses an e l ght·bit
microprocessor. To program the microprocessor, an 8 KB
programmable read-only memory (PROM) and 1KB random access memory are provided. It also has two universal synchronous/ asynchronous receiver / transmitter
(USART) Interfaces, one for console operation and one lor
remote diagnosis link operation.

Semiconductor memory offers the advantage of high
speed, especially over core memories. It also offers ease
of Interlacing to control "outside world" electronics. The
processes used to construct the storage elements within
the memory array itself can also be used for addressing
and decoding electronics and for output buffering - on a
single chip. Fewer connections mean higher reliability and
lower cost.
In the MOS memory Implementation, the storage element
takes the form of a MOS "cell" or transistor. In an elementary operation, data bits are stored by charging or not
charg ing the effective capacitance of each storage cell.
Reading entails sensing the presence or absence of
charge. Only a few hundred electrons of charge differentl·
ate the storage of a 1 and a O. Because there is capacitive
leakage, this charge must be periodically renewed or re·
freshed. The required frequency of the refresh cycle depends on leakage of the circuit, which Increases with tem-

The console Is Interlaced to the KS lObus for data and
control functions. In addition, direct connections to other
KS10 CPU modules allow the console to perform test and
housekeeping functions.
The local operator controls the KS10 with a set of commands typed at the console terminal (CTY). The CTY connects dlreclly to the microprocessor-based console hard·
ware over a serial line interlace (USAAT). A second serial

6-4

same In elther local or remote eTY caseS, except that the
remote link repertoire is restricted . In user mode, the CTY
is a user terminal, and commands are passed to and from
the KS10 CPU under control of the console program. An
exception Is typing a "control ' " which causes the console
program to switch the CTY from user mode to console
mode. All other commands performed In user mode are a
function of the operating system.
In console mode, commands are directed to an executive
by the microprocessor console hardware. An operator
can :
• Reset and bootstrap the system
• Load and check the KS 10 microcode

( ~ )

• Deposit and examine memory
• Read and write 1/ 0 device registers
• Transmit to and receive from the KS10 backplane bus
• Start and stop the CPU clock
• Single-step the CPU clock
• Execute a given Instruction
• Halt the machine
• Start the machine at a given location

Figure 6-2
KS10 Console Subsystem

line, operating In parallel with the Ilrst, can also be con~
nected to the console hardware to control the KS10 by 8
remote diagnosis link.
Commands typed at the CTY or entered from the remote
diagnosis link are Implemented by a program running In

The console program initializes the CTY to console mode
at powerup. When In console mode, either starting execution, continuing execution , or typing a "control z" will
cause the CTY 10 switch to user mode. Also, an error that
lights the fault indicator will cause a return to console
mode. as will any KS 10 processor halt Instruction.

the console's microprocessor. This program, resident in
PROM, automatically runs when power Is turned on, and Is
not destroyed when the system Is turned off.

The e TY and remote diagnosis link can be operated In
either user mode or console mode. Commands are the

6·5

7
The
Peripherals

--- --=
===
=== ===
===

DECSYSTEM-20s support a family of peripheral devices that includes
disks, magnetic tapes, terminals and terminal Interfaces, llneprinters,
card readers, and a papertape reader/punch.
The wide selection of peripheral devices reduces the storage burden
on disks and provides convenient media for file archives. Infrequently
used programs or data files can be stored on magnetic tape, which Is
easily transported and accessed. A cardreader and a papertape
reader/punch are also available for this type of 110. Using multiple
lineprinters with different characteristics can Improve hardcopy output.
The terminals supported by the DECSYSTEM-20 are the hardcopy
LA36, LA37, LA38, LA 120, and the VT100 video terminals.
A front-end processor that supports synchronous communications Is
available for DECSYSTEM-20s.
The DN200 remote station Is discussed under the heading Remote Job
Entry Stations In Section 10, Communications.

RM03 and RP06 disk drives can be mixed on the same
RHll controller on a KS10; however, they cannot be mixed
within the same logical disk structure.

DECSYSTEM-20s support four types of peripheral systems:
• Mass storage peripherals (disks and magnetic tapes)
• Unit record peripherals (lineprinters, card readers and
papertape devices)
• Terminals and terminal line Interfaces
• Communication Iront-end processors

ATP20 Disk Subsystem - The ATP20 has the largest capacity of any disk offered by DIGITAL - 929 MB per RP20
disk unit. It consIsts of a controller and an RP20 disk drive,
and can support two additional RP20s.
Each RP20 data module has fifteen recording surfaces
with two read /write heads per surface and a transfer rate
of 1.2 MB per second. WIth the optional dual-port feature,
each data module can Independently transfer data. The
AP20 Is avalleble only with KL systems.

All byte capacities In this section are calculated In 8-blt
bytes.
Peripheral devices for the KS10 (DECSYSTEM-2020)
processor are UNIBUS and MASSBUS devices that Interface to the system through UNIBUS Adapters (UBAs). The
USA Is a single extended hex module connecting to the
KS10 backplane bus and a UNIBUS. Two UBAs are standard in the DECSYSTEM-2020. One USA and one UNIBUS
are reserved lor disks. The second UBA and UNIBUS are
used for all other devices: tape, lineprinter, synchronous
communications, and asynchronous communications
lines.

Tape Devices
DECSYSTEM-2020s are available with TU77 magnetic
tape drIves. Other DECSYSTEM-20s are available wIth thIs
drIve plus the TU70 series tapa subsystems. All provide
capacities and speeds needed for a wide range of DECSVSTEM-20 applications.
All tape devIces use a mylar-based , oxide-coated magnet.
Ic tape with reflecting marker strips to Indicate Beginning
of Tape and End of Tape. Adjacent Illes are separated by
formatted Interrecord gaps. In addition, Industry-compatible formats lacllilate data transfer among computers and
can reduce hardware costs.

Detalis of the KL 10-e (DECSYSTEM-2040, 2060) 110 subsystem can be found in Section 5 under Input/Output Sub-

system.
MASS STORAGE PERIPHERALS

All tape devices provide write-protection for data that Is
read and wrItten onto the tape. An industry-standard wrIte.
protect ring Is located on the tape reel. The tape drIve can
sense write-protection and prohibit data writing.

The DECSYSTEM-20 mass storage peripherals are moving-head disk drives and magnetic tape transports.
Disks
Disk features include accurate servopositionlng, error correction, and offset pos itioning recovery. Table 7-1
summarizes the capacities and speeds of the disk devices.

Accurate data record ing and retrieval is ensured on all
tape systems with read-afler-wrllechecks. This check verIlles that proper data Is written on the tape, eliminatIng the
chance of data being written on worn or damaged sections
of tape. II an error Is detected In the read-afler·wrlte
check. a message Is sent to the processor.

To support the performance and reliability features of the
disk devices, the operating system's disk device drivers
provide comprehensive error-recovery algorithms (e.g.,
ECC and offset recovery for disk) and log all device errors.

Parity checks and longitudinal (LAC) and cyclic redundancy checkIng (CRC) further ensure the accurate transfer of
data In all magnetic tape systems. Parity Is checked character by character when reading and writing on tape at
6250 (GCA), and 1600 (PE) bits per Inch. 800 (NRZI) bitsper-inch operation also Includes a CAC character and an
LAC character. CAC and LAC characters are calculated
when a block is written and checked when the block Is
read. If an error Is detected, an Indication Is made to the
host computer.

Disk controllers allow several drives to perform simultaneous seek operations. Since the controiler Is not busy
during seek operations, data transfers on one drive can
overlap seeks In progress on other drives. II more than
one drive Is on the same controlier, overlapped seeks will
accelerate processing for disks that are on that controlier.
Overlapped seeks Increase throughput by decreasing the
effective access time.
AM03 Disk-Pack Subsystem - The RM03 Is a top-load.
lng, free-standing disk drive housed in a dedicated cabinet. Subsystems are expandable to eight disk drives or
536 MB. The RM03 has a formaHed capacity of 67 MB and
an average access time of 38 milliseconds. tts maximum
dala transler rate is 250 thousand 36-bit words per second. The disk does 18-blt NPR data transfers over a
UNIBUS and 36-blt NPA data transfers over the KS10
backplane bus (see Section 6). The RM03 Is available only
with KS systems.

All magnetic tape systems minimize bad-tape-error prob.
lems through a runaway timer that allows the system to
recover from bad tape sections on the reel.
Magnetic tape controllerslformatters perform similar operations. These include:
• Moving the tape forward or backward to a new posItion
• Monitoring tape operation
• Fetch ing. form atting, and sending data
• Handling error condillons and drIve-servicIng
requIrements

AP06 Disk-Pack Subsystem - The AP06 Is a large-capacity disk drive offering both high performance and a tow
price per megabyte of storage. It uses a removable disk
pack and has a variety of large-disk features.

rU70 Series Magnetic Tape System - The TU70 series
Is well suited for high-speed recording appllcatlons such

7-1

as JournaUng of transaction data and backup of large disk
volumes. It is a fully Integrated, high-performance system
specifically designed to operate with the DECSYSTEM-20.

UNIT RECORD PERIPHERALS
The DECSYSTEM-20 supports a full line of unit record
peripherals Including IIneprlnters and card and papertape
devices.

A system consists of one or more TU72-E 9-lrsck drives,
pius a maximum 01 eight drives, a TX02 tape control unit,
and a DX20 data channel. The lape control unit connects
to each drive with radial cabling, and the DX20 data channel connects directly to the internal data channel of the
OECSY$TEM-20.

LP20-A and -8 Llneprlnters
The lP20-A and -8 lineprinter systems have two hardware
components: an lPOS lineprinter and an lP20 lineprinter
controlier and data source Interface.
The lP05 lineprinter is a medium duty-cycle drum l ineprinter. It Is designed for data processing environments
that require good print quality and moderate print volumes. The lPOS Is an Impact-shaped (whole) character,
132-column lineprinter. It prints at 300 lines per minute
using a 64-character set or at 230 lines per minute using a
96-character set. It performs a Single forms (paper) step in
4S milliseconds (maximum) and, when formatting vertically. slews forms at up to 67.8 centimeters per second.

When reading and wrltlng in PE mode, the accuracy 01
data transfer is confirmed with character-by-character
parity checking . Error correction for single-track dropout
Is dynamic. The GCR mode uses a polynomial error-detection scheme on data blocks within each record . Data
reliablUty Is increased with a self-clocking feature that Is
independent of tape skew.
TUn MagnetiC Tapa System - The TUn is a high-performance tape storage system that is also suitable for
many hlgh-duty-cycle applications such as backup Irom
disk to tape and transaction processing. Design considerations, such as eliminating mechanical relays and Incandescent lamps on the drive and using air bearings and
ceramic guides for reduced media wear. help ensure Its
reliability. A tape interlock disables tape motion if there is
a pressure loss In the vacuum system. This feature reduces the chance of accidental tape damage.

Up to 132 characters can be slored In a print Une buffer.
Upon command from the data source, the lPOS prints the
contents of the buffer and advances the forms as specified. It signals the data source when it Is ready for the next
line of print data or forms motion command.
The lP05 uses a rotating drum contai ning all the
characters in front 01 the forms and ribbons. Fifty-eight
print hammers behind the forms are tlmeshared between
132 data columns to produce Inked characters and carbon
transfer characters on multicopy forms.

The Tun Is a fully Integrated system that is packaged In a
dedicated cabinet wllh lis associated interface and power
supply. The TU77 subsystem conSists of a TU77 tape
drive, a dual-density TM03 tape formatter, and a MASSBUS controller that mounts in the processor chassis. Each
subsystem can Include up to four tape drives with a total
maximum 0lt6 drives per DECSVSTEM-20.

The LPOS contains a 12-channel programmable vertical
format unit (PVFU). It uses a format memory that Is loaded
from the data source. so no lormat tape Is installed by the
operator and there is no risk Of running a job with the
wrong format tape. The PVFU can be loaded each time
data Is requested by the printer. Format memory data and
control codes are transm itted to the printer via the normal
data lines using the standard demand /strobecommunicalions. The PVFU can control the vertical movement 01
forms having eight to 143 Jines.

Automatic tape threading maximizes operator convenience and minimizes tape handling. Smaller reels of tape
can be threaded automatically when tape Is placed manually In the loading slot. II a to.S-lnch reel of tape falls to
load on the first attempt, the TU77 will detect the mlsfeed
and reload without operator Intervention.

The lPOSlineprlnter has switches and Indicators lor operallon and operator-level maintenance. When the print
TEST/ ONLINE switch Is set to TEST, the self-test module
operates as a built-In data source. The printer communicates with the self-test module on a demand/strobe basis.
stores the data received in the line buffers and paper molion registers, and processes the data. After the line of
data has been printed and the paper moved . the printer
resumes the data exchange communlcallon with the selftest module In a continuous cycle.

The TU77 subsystem also promotes data Integrity through
automatic correction of single-track errors. In PE mode,
this error correction Is done automatically by the hardware. In NRZI mode, error correction Is performed under
software control.
The TU77 reads in forward and reverse and uses the
industry-standard data format.
Table 7-1
Disk

Typ.

Disk Devices

Capacity

Peak

Average

Averege

IMbyte)'

Tren,',r Rete

S •• klima

Rotational

(Kbyte' a)'

(ma)

letency

Intertace

Mllimum
Drl"es per
Controller

(m.)
AM03

Removable

1,200

8.30

MASSBUS

RP06

Removab le

178

806

8.'

MASSBUS

RP20

Nonremovable

929

1.200

8.'

MASSBUS

• K - 1,024; M - 1,024 "

t 2 spindles per drive

7·2

A long-line interface provides the lP05 with differential
receivers and drivers so that 11 can be located up to 30.5
meters (100 feet) from the data source. A standard 7.6meter (25-fOOI) device cable Is normally supplied.

approprlale, and processes the data. After the line of data
has been printed and the paper moved, the printer resumes continuous cycle data exchange communication
with the self-test module.

lP20-C and -0 lineprinter.
The lP20-C and -0 lineprinter systems are composed of
an lP14 lineprinter and lP20 lineprinter controller and
data source interface.

LP200 Lineprinter.
The lP200 lineprinter system has two hardware components: an lP07 lineprinter and an lP20 lineprinter controller and data source Interface.

The lP14 lineprinter Is a medium duty cycle drum lineprinter. It's designed for use In data processing environments
that require good print quality and medium prInt volumes.
The lP14 Is an Impact type, shaped (whole) characler,
132-column lineprinter capable of prInting six or eight
lines per Inch. II will produce printed output al 890 lines
per minute using a 64-characler set, or 650 lines per
minute using a 96-character set. It performs sIngle forms
(paper) step in 20 ms (max) and slews forms at up to 76.2
cm (30 Inches) per second when formatting vertically.

The LP07 Is a high-performance, horizontal font motion
lineprinter designed for data processing environments requiring high-grade print quality, heavy print volumes, and
high reliability.
The LP07 Is an impact-shaped (whole) character, 132-column lineprinter. It prints 990 or 1,220 tines per minute
usIng a 96-character set and 715 or 905 lines per minute
with a 96-character sel. Print speed Is operator-selectable.
The LP07 does a single forms paper step In 12.5
milliseconds and slews forms vertically at up to 152.4 cm
(60 In) per second.

The lP14 lineprinter stores streams of up to 132 characters In a print-line buffer, and, upon command from the
data source, prints the contents of the buffer and advances the forms as specified by the command. It slgnats
the data source when It's ready for the next line of print
data or forms-motion command.

Up to 132 characters can be stored In a print line buffer.
Upon command from the data source. the LP07 prints the
contents of the buffer and advances the forms as specified. It signals the data source when It Is ready for the next
line of print data or forms motion command.

The lP14 contains a 12-channel programmable vertical
format unit (PVFU). The PVFU uses a format memory that
is loaded from the user system. This relieves the operator
from having to Install a format tape and eliminates the risk
of running a print job with the incorrect format. The PVFU
may be loaded at any time data Is requested by the printer.
Format memory data and control codes are transmitted to
the printer via the normal data Unes using standard demand/ strobe communications. The PVFU can control the
vertical movement of forms having from eight to 143 lines.

The lP07 uses a Charaband- as the horizontal font carrier
in front of the forms. One hundred thirty two print hammers, behind the forms and the ribbon, produce the Inked
characters and carbon transfer characters on multlcopy
forms. The Charaband has the advantages of train printers, but minimizes the prOblems of character set rigIdity,
friction, and wear associated with other horizontal font
techniques.
The Charaband has two complete character sets, one on
each side. A one-minute manual operation switches the
sets.

The lP14 lineprinter Includes an operation/maintenance
panel that mounts switches and Indicators to operate the
lineprinter and perform operator-level maintenance.

The LP07 lineprinter contains a direct-access vertical form
unit (DAVFU) that provides the same benefits as the PVFU
discussed In the LP20 section above. The OAVFU also
permits print density of six or eight lines per Inch under
program control.

A self-test module ailows the printer to be tested under
dynamic conditions. When the printer TEST/ON- LINE
switch Is set to TEST, the sell-lest module acts as a built-in
data source: I.e., the printer communicates with the selftest module on a demand/strobe basis, stores the data
received In the line buffers and paper motion registers, as

Tape

Reel
Siu

Capaclly

(Mbyle)"

Column
Buffering

(In)

• Charaband Is alrademark 01 Data products Corporation

Table 7-2

Tape Oevlcea

Recording
Density

Read!Wrlte
Speed

Maximum Oall
TrlnaferRlle

Rewind
Speed

(bltalln)

(Inla)

(10~ch.r/a)

(In/e)

Inlerface

TU72

g-track

10.5

Vacuum

1,600/6,250

125

750

500

MASS8US

Tun

9-track

10.5

Vacuum

BOO/I,600

125

200

440

MASS8US

M - l,024"

t Program.selectable
7-3

Maximum
Orlvea per
Controller

,
•

The LP07 contains a self·test unit similar In function to the
unit discussed in the LP20 section above.

talns a 36-word buffer from which aU data Is retrieved by
the processor.

A iong.llne interface provides the LP07 with differential
receivers and drivers so that It can be located up to 152
meters (494 feet) from the data source. A standard 7.6·
meter (25-foot) device cable Is normally supplied.

At 300 lines per second , the reader takes 3.33 milliseconds
per alphanumeric character and 20 milliseconds per conIIguous word.

Cardreader.
The CD20 cardreaders read encoded, punched information using the American National Standard 8-bit card code
and Interprets a special punch outside the data representation to indicate end-of-flle. The cardreaders use the Industry-standard EIA card that has 80 columns and 12
zones, or rows.

TERMINALS AND INTERFACES
A KS system supports a maximum of 32 local and remote
line interfaces. A KL system supports up to 128 local and
remote lines. Programs can control terminal operations
through the terminal driver. The terminal driver receives
and services Interrupts. Initiates lIO operations, cancels
In-progress lIO operations, and performs other devicespecific functions. A program can:

The cardreaders are designed to meet different throughput requirements. CD20 card readers are available In both
table (CD20-A) and console (CD20-C) models. CD20-A
can process 285 punched cards per minute, and the
CD20-C , 1,200 cards per minute.

• Get data from an open terminal without stalling program
execution . The program doesn't have to walt lor incomIng data to be available In the terminal Input buffer.

The CD20-A tabletop unit has an Input hopper capacity of
1,000 cards and the CD20-C. 2,250 cards. They are designed to prevent Jams and keep card wear to a minimum.
These readers also have a high tolerance for cards thllt
have been nicked, warped . bent, or subjected to high
hum idity. Readers use a short card path. with only one
card In the track at a time. They all use a vacuum-pick
mechanism that keeps cards from sticking together by
blowing a stream of air through the bottom half-Inch of
cards In the Input hopper.

• Translate, Interpret, and transmit ESCAPE sequences.

• Through echo control mode, using a full-duplex terminal. simulate the operations of a blockmode terminal.
Input data from the terminal Is processed a field at a
time. without affecting the displayed output In other
field s on the screen .
In addition, pseudotermlnals can be used for jobs, such as
batch . that do not require operator intervention. A pseudoterminal has the characteristics of a terminal but has no
physical device attached to It. Like a terminal, a pseudoterminal has both Input and output buffers. By using pseudotermlnals, one job can control other jobs on the system.

The CD20-C console card reader has a single-piece read
stalion with Infrared light-emitting diodes, em itters, and
phototranslstor detectors. No adjustments are required In
the ten-year life expectancy of the diodes.

Terminal characteristics are Initially established In a command file during software installation. However, system
users also can modify the characteristics of their particular
terminal. For example. users can:

The console model also provides high data integrllywlth a
"resync / error detection" feature. The data strobe can be
resynchronlzed lor each data column. The reader will either correctly read a mlsreglstered card or reject the card
by halting with a "read check" Indication.

• Set the width of tha print line between 1 and 255
columns. The system automatically generates a carriage
return and IIneleed sequence after the specified number
of characters has been typed or printed.

Cards can be loaded or unloaded while the console model
is operallng. A switch can be set to provide either blower
shutdown or continued running after the last card has
been read. Automatic shutdown reduces computer room
noise levels and can also signal the operator that the card
hopper Is empty.

• Control transmission 01 upper- and lowercase characters.
• Allow the computer to Interrupt transmission of characters from the term inal (XOFF) or Instruct the terminal to
resume transmission of characters (XON). The terminal
hardware must be present to respond to XOFF and XON
characters.

PC20 Paper Tape Reader/Punch
The PC20 raad s eight-channel papertape at 300 lines per
second and punches at 50 lines per second In either alphanumeric or binary. It automatically fan-folds the paper
tape.

• Set the rate at which the terminal's interface can accept
or pass characters.
• Set even , odd , or no parity checking.
A line entered on a command terminal is terminated by
any of several special characters. The RETURN key, for
example, is one of the most common means of transmitting a command to the host. A program reading from a
term inal can specify a particular line terminator for read
requests.

The PC20 contains a photoelectric papertape reader and
an electromechanical punch. A set of photodlodes translates the presence or absence of holes In the tape to Is
and as.
In alphanumeric mode, a single tape-moving command
reads aU eight channels from the first line encountered . In
binary mode. the device reads six channels from the first
six lines in which hole 8 Is punched and then assembles
the Information Into a 36-blt word . The PC20 Interface con-

LA 120 Hardcopy Terminal
The LA 120 Is a hardcopy terminal with high throughput
and a number of advanced keyboard-selectable formatting and communication features. It uses a contoured.

'·4

set and changed by the host computer or by the user. The
LA38 has a permanently stored format for a computer
printout. When the terminal Is powered up, It automatically
Is set to print ten characters per Inch and space six vertical
lines per Inch, set tab stops every eight spaces, set the lett
margin at column 1 and the right margin at column 132.
The LA38 operates at 300 baud and can print at burst
speeds up to 45 characters per second. An alternate
speed of 110 baud and 10 characters per second can be
selected from the keyboard. The desktop configuration
and sculptured typewriter-like keyboard are so similar to
standard typewriters that the transition from typewriter to
terminal Is natural.
The terminal's basic design contributes to lis reliability and
maintainability. Logic and power amplifier on a single
board with custom LSI reduces the component count and
increases circuit reliability.
The LA38 senses prlnthead Jams Instantly and shuts down
power to the prlnthead drive until the Jam Is corrected and
the terminal restarted . This prevents motor overloads and
blown fuses. The highly reliable prlnthead has been designed and tested to print more than 100 million characters. The prlnthead can be adjusted to adapt to various
form thicknesses. The LA36 Is equipped with a paper-out
sensor that, when enabled , Implements one of four selectable actions when there is a paper fault.

typewriter-style keyboard, an additional numeric keypad,
and an LEO display lor terminal characteristics.
Several features give the LA120 Its high throughput:
• 180-character-per-second print speed
• 14 data transmlsslon speeds ranging up to 9,600 baud
• l ,024-character buffer to equalize differences between
transmission speeds and print speeds

Although the LA36 has no scheduled preventive maintenance, should a problem occur, the unit disassembles
Simply and quickly for easy access to all components.
Printing self-test diagnostics allows quick and accurate
Identification of any faulty components. With the new
snap-In ribbon cartridge, users can change ribbons quickly and easily.

• Smart and bidirectional printing so that the printhead
always takes the shortest path to next print position
• High-speed horizontal and vertical skipping over white
space
In addition to Its throughput, the LAt20 is distinguiShed by
its printing features. The terminal offers eight font sizes
ranging from expanded (live characters per Inch) to compressed (16.5 characters per Inch). Hence, a user could
select a font size of 16.5 characters per inch and print 132
columns on an 6.25-lnch-wlde sheet. Other print features
Include six line spacings ranging from two to 12 lines per
Inch, user-selectable form lengths up to 14 Inches,
left/right and top/bottom margins, and horizontal and
vertical tabs.

Wherever possible, ANSI standard escape sequences are
used. These same escape sequences are also Implemented on DIGITAL's LA 120 and VT100, ensuring compatibility
among DIGITAL's terminal products.
VT100 Video Terminal
The VT100 video terminal Is an uppercasellowercase
ASCii terminal that offers a variety 01 user-controllable
character and screen attributes. The VT100 features a
typewriter-like detachable keyboard that Includes a standard numeric/ function keypad for data entry applications.
Also featured are seven LEOs, four of which are programcontrolled , that can be used as operator Information and
diagnostic aids.

The LA 120 Is designed lor easy use. Terminal characteristics are selected via clearly labelled keys and simple mnemonic commands. Once the selections have been made,
the operator can check the settings by depressing the
STATUS key. The terminal will then print a listing of the
selected settings.

The VT100 offers a number of advanced features. The
most Important of these are:
• Two screen sizes - 24 lines by 60 columns or 14 lines
by 132 columns
• Une-by-line selectable characters of regular size, double width and single height, double height and single
width, or double width and double height

LA38 HardcopyTarmlnal
The LA36 DECwrlter IV Is a low-cost, desktop microprocessor-driven terminal capable of proceSSing data at up to
30 characters per second. The LA36 Includes a universal
power supply, a standard EIA Interlace and EIA null modem cable, an 18-key numeric keypad, paper-out switch,
paperleed tractor, and user-assistance documentation
package.

• Smooth scrolling and split-screen capability
• Keyboard selectable and storable baud rales, labs, and
Answer Back messages
• Special line-drawIng graphic characters for business or
laboratory applications

Features such as horizontal tabs and margins, and a
choice of four character sizes and six line spacings can be

'·5

• Selectable black-on-whlte or whlte-on-black characters
on a full-screen basis
Several optIons further extend the capabilities of the
VT100. These Include the advanced video option that adds
selectable blinking, underline, and dual-intensity characters to the existing reverse video aHrlbute, and an additional RAM module that enables 24 lines of 132 characters.
elll Terminal lin. Interface (KS syst.ms)
The OZII Is a serial line multiplexer whose character formats and operating speeds are programmable on a perline basis. A DZll connects the UNIBUS with up to eight
asynChronous serial lines. Each line can run at any of 15
speeds.
local operation with EIA terminals Is possible at speeds up
to 9,600 baud. The DZll can be used with dialup fullduplex terminals that operate through most Industry-standard modems running at 300 or 1,200 bits per second. The
OZ11 optIonally generates parity on output and checks
parity on Input. Incoming characters are buflered using a
64-character silo buller; outgoing characters are
processed on a programmed Interrupt request basis.

DUP11 Single Synchtonousllne Interface
(KS systems)
The OUP11 Is a character-buffered, synchronous, serial
line Interface capable of two-way simultaneous communication. The OUPll translates between serial data and
parallel data. Output characters are transferred in parallel
from the POP-l1 UNIBUS Into the DUPll where Ihey are
serially shifted to the communication line. Input characters
from the resident modem are Shifted Into the DUP11 and
made available to the processor on an interrupt basis.
The self-contained unit Is capable of handling a variety of
protocols. These Include byte-oriented protocols, such as
OOCMP and BSe, and bit-oriented protocols, such as
SOlC, HOlC, and AOCCP. Signals needed to establish
communications with the Bell Series 200 synchronous modems are resident In the DUP11's Receive Status Register.
The OUPII can transmit data at up to 9,600 bits per second (limited by modem and data set Interface level
converters).
Its capablllties make the DUP11 well suited for remote
batch, remote data collection, remote concentration, and
network applications. In addition, multiple DUP11s can be
used in applications requiring several synchronous lines.

CH11 Programmable Asynchronous Serial line
Multiple .. r (KL systems)
The DH11 multiplexer connects the UNIBUS with 16 asynchronous serial communications lines. The DH111s a hlghperformance unit with programmable character formats
and operating speeds. Data Is buffered on input and is
transferred directly from memory.

KMC11-A Auxiliary Processor (KS system)
The KMC11-A is an auxiliary processor, complete with
memory, that Interfaces to the UNIBUS. The KMC11 Improves the performance of the OECSYSTEM-20 computer
systems by performing time-consuming syslem functions
In parallel with the host CPU, thereby offloadlng It. It Is
especially suited to contrOlling I/O operations, such as data communications and analog 1/0, that require extensive
intelligence.

Program-selectable parameters Include transmission
speeds up to 9,600 baud, character size, stop-code tength,
transmission mode, and parity generation and checking.
An optional modem control multiplexer is available lor
connecting the DHll to an autoanswer data set.

The KMCll Is a high-speed MSi microprocessor (3oo
nsec Instruction time) that uses 16-blt mlcrolnstructfons
and operates on B-blt data paths. Its 1,024 16-blt word
writable control memory that contains the microprogram
is loaded by the host processor. A 1,024 B-blt byte data
memory stores frequently used Information for high-speed
access by the microprogram. An NPR UNIBUS Interface
provides access to control, status, and data registers of
one or more peripherals on the UNIBUS. This enables lowcost programmed 110 devices to operate as if they had an
Intelligent OMA capabltlty.

As many as eight DHlis can be placed on a single processor for a total capacity of12B lines.
Ol11 Serial line Asynchronous Interfaces
The Ol11 Is an Interface between a single asynchronous
serial communication channel and the processor. II performs serial-la-parallel and parallel-to-serial conversion of
serial start/stop dala with a double-character-buffered
MOS/lSI circuit called a UART (universal asynchronous
receiverltransmllter). This 40-pJn, dual inline package has
all the circuitry necessary to dOUble-buffer characters In
and out, serialize/deserialize data, select character length
and stop code configuration, and present status Information about the unit and each character.

The KMC11 can be directly connected to a high-speed
peripheral such as a OMCll synchronous line unit. The
full-duplex B-blt parallel Interface is well suited to custom
designed Interfacing.

DN20 COMMUNICATIONS FRONT-END

With a Ol11 Interface, a DECSYSTEM-20 can communicate with a local terminal, such as a console teleprinter,
and with a remote terminal via data sets and private line or
public switched telephone facftilles.

The DN20 is designed to handle all network communication functions. The ON20 Is referred to as a communication
Iront-end to distinguish It from the console front-end that
controls the local command terminals and unit record perIpherals. The ON20 and console front-end processor
communicate with the Kl processor through the OTE
hardware Interface. The OTE resolves the differences
between the 36-bll Kl word and the 16-blt ON20 word . In
systems with the KS10 processor, the communication software resides In the processor.

Users can select from 13 standard data rates up to 9,600
baud or can select a nonstandard rate. With most of Ihe
standard rates, the Interface can offer split-speed operation for faster, more efficient handling of computer output.
In addition, character size Is strap- or switch-selectable,
and parity checking and stop code length are selectable.

'-6

•

8
The
Languages

In addition to the MACRO assembly language, the TOPS-20 system
software supports the optional high-level programming languages

FORTRAN . COBOl-G8. COBOl-74 . ALGOL. BASIC-PLUS-2. APl.
BLISS, and CPL. This variety gives the user the most effective or
familiar programming solution to match the problem .
FORTRAN-20 Is both a globally optimizing complier and a runtime
system with an interactive debugger and subroutine library. It has been
designed 10 simplify the programmer's Job, provide superior complletime and runtime diagnostics, facilitate debugging , and produce errorfree and fast-runn ing programs.
COBOL-68 and COBOL-74 are high-level Implementations designed
specifically for business data processing . COBOL can be used to
create online terminal applications or to write batch applications.
Although BASIC-PLUS-2 is an Ideal language for novice programmers
who need a fast, easy way to solve problems, It Is also a powerful and
efficient language suitable for sophisticated applications. BASICPLUS-2 is a complier that produces fast-running programs, yet It
reta ins the highly interactive immediate mode feature of primitive

BASIC.
ALGOL-20 is a scientific language designed for describing algorithms.
It is a problem-solving language In which the problem is expressed as
complete and precise statements of a procedure.
Two levels of the popular APL language are available. Both are full APL
implementations with significant extensions . The basic version suits
users who do not require the file 110 or the advanced APL function . The
extended version, APL-SF, has all of the features of the basic version
plus advanced features that substantially Increase the range of
applications In which It can be used.
BLlSS-36 is DIGITAL's Implementation language for software
development. It contains many of the features of a modern, high-level
language. yet It also provides the flexibility and access to hardware of
assembly language.
CPL (Conversational Programming Language) is an interpreter similar
to PUI . It Is a well documented and easy-to-Iearn subset of ANSI-1976
Pli I.

TOPS·20 ASSEMBLER

FORTRAN

MACRO Is the DECSYSTEM-20 symbolic assembly language. It makes machine language programming easier
and 'aster for the user by:

FORTRAN-20 Is a globally optimizing complier and a
runtime system with an interactive debugger. Both have
been designed to simplify the programmer's job, provide
superior compile-time and runtime diagnostics, facilitate
debugging. and produce error-free, fast-running programs.

• Translating symbolic operation codes In the source program Into the binary codas needed In machine language
Instructions
• Relating symbols specilled by the user to stored addresses or numeric values

FORTRAN-20 Is based on the 1966 American National
Standard (ANSI) FORTRAN, but It has many extensions to
that standard and Includes many features from the ANSI
1977 FORTRAN . Both the complier and object-time system are reentrant (sharable). FORTRAN features Include:

• Assigning relative core addresses to symbolic addresses of program Instructions and date
• Provid ing a MACRO expansion capablllty to facilitate
storage, definition, or user-defined Instruction
• Providing a sequential numbered listing with symbols
cross-referenced to show where they are defined and
where they are used

• Accepted and powerful features useful to a wide range
of technically oriented users
• Computational faatures matched by full-scale data handling and data management facilities

MACRO programs consist 01 8 series of free-format state-

• Globalopllmlzatlon
• PARAMETER statements that provide symbolic specification of compile-lime constraints
• INCLUDE statements to compile source code from more
than one file

ments that can be prepared on the user's terminal with one
01 the system's edIting programs. The assembler Interprets and processes these statements, generates binary
Instructions or data words, and produces a listing that can
contain cross-reference symbols for ease In debugging
the program . MACRO produces device-Independent programs. It enables the user to select, at runtime. standard
peripheral devices for Input and output Illes. For example,
Input of the source program can come from the user's
terminal and output of the program listing can go to the
lineprinter. More commonly, the source program Input
and binary output are disk Illes.

• N-dimensional arrays
• Optionally generated array bounds checking
• Direct-access 110 capabilities
• Debugger that permits examining and modifying program data, statement-by-statement program tracing,
and setting pauses on any statement or routine
• OPEN and CLOSE statements for liIe specification and
control

The MACRO assembler contains powerful macro capabilities that enable the user to create new language elements.
This is useful when a sequence of code Is used several
times with only certain arguments changed. The code sequence Is defined with dummy arguments as a macro instruction. Thus. a single statement In the source program
referring to the macro by name, along with a list of the real
arguments, generates the enllre sequence needed. This
capability permits the expanSion and adaptation of the assembler to perform specialized functions for each
programming job. In addition, changing the macro dellnition changes It for every call.

• ENCODE/ DECODE statements
• Boolean operators, Including equivalence and exclusive
NOR, OR, AND, and NOT
• NAMELIST statement and list-directed 110 that provide
lormat-Iree Input and output operations
• Implied DO loops In 110 and data statements
• Full , mixed-mode arithmetic In expressions
• Octal constants
• Full-word masking operations lor all logic functions
(rather than a result of Just true or false)
• Relational operators
• Error-handling capabilities in 110 statements
• Device Independence
• Multistatementllnes
• Remarks In statement fields

DEBUGGING TOOLS
The online symbolic debugging tool (DDT) enables a user
to rapidly check and correct a new program. To do this,
the source program Is assembled and the resulting binary
object liIe with its table of dellned symbols Is loaded with
DOT. Using command strings, the user specifies breakpoints In the program where DDT suspends execution to
accept further commands. This segments the program Into executable sections that can be Individually checked
and corrected. Either before DOT begins executing or at
breakpoints, the user can examine and modify the contents of any location In the program. DDT also performs
searches, gives conditional dumps, and calls user-coded
debugging subroutines at breakpoint locations.

The FORTRAN object-lime system. FOROTS, controls the
Input/ output, format interpretation, and numerical conversion for programs complied by the FORTRAN complier.
The FORTRAN user can reference any mass storage, unit
record, or terminal device. All special editing, conversIon,
and fIIe·structurlng tasks are handled by the object-time
system . Devices are normally specified by logical assign·
ment, so that physical device selection need not be made
until runtime. The devices corresponding to the specific
110 statements - READ, PRINT, PUNCH, ACCEPT, and
TYPE - are also assignable at runtime.

The Important feature of DDT Is that users communicate
with It In terms of the original symbolic iocatlon name,
rather than the machine-assigned locations.

8·'

Language Extensions
Powerful FORTRAN IV extensions simplify program cod·
Ing. Some of the enhancements are:
• Array subscripts - any arithmetic expression can be
used. lithe value of the expression Is not an Integer, it Is
converted to Integer type.
• Alphanumeric literals - strings of characters bounded
by apostrophes that can be used In place of Hollerith
constants.
• Mixed-mode expressions - can contain any data type,
including complex and byte.
• End-of-line comments - any FORTRAN statement can
be followed on the same line by a comment that begins
with an exclamation point.
• READ/ WRITE end-of-file or error condition transfer END - n and ERR - n (where n Is a statement number)
can be Included In any READ or WRITE statement to
transfer control to the specified statement upon detection of an end-ol-Ille or error condition. The ERR '"' n
option Is also perm itted in the ENCODE and DECODE
statements, allowing program control 01 data format
errors.
• General expression DO and GO TO parameters - general expressions are permitted for the Inllfalvalue, Increment, and limit parameters In the DO statement and as
the control parameter In the computed GO TO statement.
• DO Increment parameter - the value can be negative.
• Optional statement label list - In an assigned GO TO.
• Default FORMAT widths - Input or output formatting
can be specUied by type and default width, and precision values will be supplied.
• Additional 110 statements - these Include file conlrol
and attrlbule definitions. list-directed (free-format) 110,
device-oriented l I D , memory-to-memory formatting ,
and unformalted direct-access 110 10 read and write
liles written In any' lormat.
• Logical operations on INTEGER data - the .AND., .OR. ,
.NOT., .XOR., and .EQV. logicat operators can be applied to Integer data lor bit mask ing and manipulation.

Debugging Tool.
Three debugging facilities are avaJlable to the FORTRAN
programmer: FORDDT debugger. the FORTRAN obJecttime system, and the use 01 a "0" in Column 1 01 a FORTRAN statement.
Using FORDDT, a programmer can set up to 10 runtime
breakpoints on subroutine entries or on source statement
labels or line numbers. The programmer can also conlJOue
from a breakpoint, display and change the value 01
variables. locate symbols, execute sourCe lines, and dispiaya trace of subroutIne calls.
The debugger commands are similar to FORTRAN statements, so that programmers can easily learn and use
them.
With the exception of a IIne-by-line trace or the Inclusion 01
PAUSE statements, none 01 the FORDDT debugging features Increases the execution Ume of a program. FORDDT
also provides an entry into the system debugger, DDT.
The FORTRAN ob/ect-tlme system (FOROTS) provides a
traceback feature that locates and lists the actual program
unit and line number of a fatal runtime error. II the program unit Is a subroutine or function subprogram, the error handler traces back to the caJUng program unit and
dIsplays the name of that program unit and the line number where the call occurred. This process continues until
the calling sequence Is traced back to a specific line
number in the main program. The traceback feature helps
the programmer to determine the exact locallon of an error. even if It occurs in a deeply nested subroutine.
A " 0 " In Column 1 of a FORTRAN statement allows that
statement to be conditionally complied. These statements
are considered comment lines by the complier unless the
appropriate debugging line switch Is Issued In the compiler command string.
Liberal use of the PAUSE statement and selective variable
printing provide programmers with a method of monitorIng program execution. This allows the Inclusion of debugging aids that can be complied In the early program testing
stages and later eliminated w ithout source program
modification.

COBOL

Optimization
The FORTRAN-20 compiler uses optimization to produce
an object program that gives the same results as the original unopllmlzed program, but takes significantly less execution time.

COBOL-68 and COBOL-74 are optional high-level languages designed specifically for bUSiness data processIng. COBOL can be used to create online terminal appllcalions or to write batch applications. Under control 01 the
mullistream batch processor or from an Interactive terminal, program and data decks can be loaded Into the
cardreader for spooling operations. Both methods use the
same command language.

Opllmizatlon techn iques Include:
• Ellmlnallng redundant computations
• Substituting arithmetic operations with operations that
take less lime
• Removing constant computations from DO loops
• Folding and propagallng ~onstants
• Removing Inaccessible code
• Allocating global registers
• Optimizing 110
• Detecting unlnltlaJized variables

COBOL features include:
• ANSI-standard compliance
• Quick. efficient program development
• Simple, interactive user application Interface
• Efficient operation in both batch and online operallon
• Programming tools with powerful, easy-to-use data editIng, sorting, updating , and reporting features

8-2

- - - --'--

r
The program can receive U6er Input lines with the ACCEPT
statement. The ACCEPT statement also can retrieve the
current date or time from the system.
The DISPLAY statement transfers data from a specified
literal or data item to a specified device, normally the
user's terminal. The DISPLAY WITH NO ADVANCING
statement inhibits the automatic appending of a carriage
return and line feed to halt the device atter the last charac·
ter Is displayed. This Is especially useful when typing
prompting messages on the terminal.
File Orgenl1.8tlon
The sequential 110, relative 110, and Indexed 1/0 modules
meet the ANSI-74 high-level standards, except as Indicated In Table 8·1, and Include all the COBOL verbs.
The COBOL object-time system includes a complete Indexed sequential access mode (ISAM) package to enable
the user to access data either sequentially or randomly by
key value on random-access devices. The time required to
access a lIIe Is minimally affected by the number of additions made to the lIIe. The technique of "chaining" records
Is not used . Instead, the Index to the file Is updated to
minimize the number of accesses necessary to retrieve
records.

• Remote access from online terminals or from remote
statlons
• Complete program and device independence for eftl·
clancy and rellabillty
• Ability to cali subroutines written in-COBOL, FORTRAN,
or MACRO

Library Facility
With COBOL, programmers have a full ANSI-74 high-level
library facility that includes high-level extensions (COPV ... REPLACING). Frequently used data descriptions and
program text sections can be held in library files that are
available to all programs. These lUes can be copied at
compile lime to reduce program preparation time and to
eliminate a common source of errors.

listings produced by the complier contain many documentation and debugging aids. English diagnostic messages are embedded in the source listing at the point of
error. The listing can also include, at the user's discretion,
8 complete map of the object program and an easily read
listing of the complied code similar to thai used by the
MACAO assembler. All object code Is expanded to list the
machine mnemonics and user-defined names in addition
10 the binary machine code (In octal). There Is also an
Implementallon of the COBOL REPORT WRITER

ENTER Faclilty
The ENTER statement allows COBOL programs to Invoke
separately complied subprograms, passing arguments In
the process. These subprograms can be written In
COBOL, FORTRAN, or MACRO. The ENTER facility:
• Provides flexibility through modular development of application systems
• Permits functional separation 01 small , well defined
source modules
• Gives the programmer access to operatlng-system.dependent features via subroutines written in MACRO

statement.
Data Types
COBOL supports all of Ihe common COBOL dala types,
includ ing:
• Numeric COMp-3 packed decimal
• Numeric COMPUTATIONAL (COMP) binary
• Numeric COMPUTATIONAL-l (COMP-l) floating point
• Alphanumeric DISPLAY (ASCII , EBCDIC, or SIXBIT)

• Numeric DISPLAY (ASCII , EBCDIC, or SIXBIT)

Online Oebugger
The online COBDDT debugging package permits user in·
teraction during the execution of a program. Source pro·
grams require no modifications to use COBDDT - it Is
simply loaded with the object program when execution
starts. The user can specify points within the program at
which to pause during execution, so that the user can examine and modify the contents of data Items belore
proceeding. All references to data and procedure items
are made by using the name In the source program. The
user talks to the debugging package with familiar names
rather than truncated or substituted names.

These data types are required in a variety of applications
and are provided lor lIexlbility In specification and design.
String Manipulation
COBOL provides INSPECT, STRING , and UNSTRING
verbs for handling character strings. With these verbs programmers can search for embedded character strings
with TALLY and REPLACE. The verbs can Join together or
break out separate strings with various delimiters.
Interactive COBOL Execution
The ACCEPT and DISPLAY statements of the PRO·
CEDURE DIVISION enable easy, termlnal·orlented Inter·
action between a COBOL program and the program user.

Source Program Input
The disk-resident complier can accept source program

8·3

ALGOL-20

input from all supported input devices, including source
text library files stored on disks.

AlGOl-20 Is a scientific language designed for describing
computation processing or algorithms. It Is a problemsolving language in which the problem is expressed as
complete and precise statements of a procedure.

COBOL accepts source programs that are coded using
either Ihe conventional 60-column card reference format
or the short, easy-to-enter terminal format.

The TOPS-20 Interactive editors and an Integrated ALGOL
debugger make It easy to code, test, and debug programs.
Program modularity Is available through block structure,
subprograms, and separately complied procedures.

Terminal Format Is used with context edItors controlled
from an online terminal keyboard. It eliminates the line
number and identification fields and allows horizontal tab
characters and short lines. These capabilities offer potential savings In disk space and allow easier Interactive input
01 source programs.

AlGOl-20 is an Implementation of the ALGOL-GO language. The compiler consists of a 14K-word reentrant
(sharable) segment and a data segment that varies In size
depending on the size of the program to be complied. The
one-pass, single-phase complier produces diagnostics
and generates optimized object code.

Conventional Format produces source programs that are
compatible with the reference format of other COBOL
compliers throughout the Industry.
RERUN
RERUN allows the user to periodically save the status of a
job. In the event of a later dIsruption the lob can be restarted from the point of the last status saved Instead 01 from
the beginning.

AlGOl-20 language features Include:
• long reel scalars, arrays, and procedures using the
double-precision hardware with 52-bit mantissas
• String scatars, arrays, procedures, and byte manipulation for users to generate, manipulate, and input or out·
put strings or Individual bytes ranging In size from one to
35 bits
• Assignments within expressions
• A remainder operator
• Unique Implementation of dynamic arrays
• Octal Boolean constants and integer·ta-Boolean and
Boolean-to-Integer conversion functions

COBOl-68 and COBOl-74
COBOL on DECSYSTEM-20s is available In two versions:
COBOl-68 and COBOl-74.
COBOl-68 Is an Implementation 01 the COBOL language
based on the ANSI COBOL X3.23-1968 standard. COBOL74 Is an Implementation of the COBOL language based on
the ANSI COBOL X3.23-1974 standard. COBOl-74 meets
the high-level requirements of Federal Information Processing Society (FIPS) PUB 21-1 as tested by the FCCTS
(Federal COBOL Compiler Testing Service) with the exceptions noted In Table 6-1 .

Table 8-1

• WHilE statement and a convenient abbreviated form of
the FOR statement
• The ability to call FORTRAN language subroutines and
lunctions
• Identifiers up to 54 characters long

COBOl-74 Support levels

AN5-74
Module

level
Supported
byCOBOl·74

FIPS Pub 21·1
" High level"
Requirements

Nucleus

Table Handling

Sequenllall/O

Relative 1/0

Indexed 110

2·

Segmentation

Library

Debug

Interprogram
Communication

SORT/MERGE
Communication

2
2

Report Writer

Block Structure
The ALGOL program structure Is somewhat more sophisticated than some other high-level languages such as
FORTRAN or BASIC. ALGOL programmers can effectively
use structured programming techniques. An ALGOL program has a number of hIerarchically arranged blocks con·
sisting of declarations and statements enclosed by the
words BEGIN and END. Scope rules and declarations determine which variables are global and which are local to a
block .
Block structure offers many advantages Including easier
Implementation of top-down application design, code mo·
dularlty, easily read and understood programs, and Increased protection from side effects.
Procedures
ALGOL procedures are subprograms that are useful In
writing highly structured, easily read programs. Code segments that are used more than once, and lo r that can be
viewed as a module of the larger program , can be
separated Into procedures. To aid top-down program development, procedures can be written, debugged , end
complied separately from the main program. large structured programs frequently consist of a series of procedure
calls.

• Alternate kay not supported

t Debug module Is functionally rap laced by CaBOOT

Not supported

§ ANSI-66 Report Writer syntax plus SUPPRESS statement

8-4

Parameters can be passed to a procedure by value or by

length of the string Is limited only by available memory.
String constants are typically used to convey messages to
the program users or to assign value to string variables.

nama. When an expression In a procedure call (an actual
parameter or argument) Is passed by value, a copy of its
value Is made available as alocsi, formal parameter (dummy varIable) within the procedure. This is an eHlclent way
to pass many expressions and to protect the calling block
from side effects.

Object-Time System
The AlGOL-20 object-time system (AlGOTS) provides a
basic InpuUoutput system so that the user can communicate with dlrectorled and nondlrectorled devices In ASCII
and binary modes.

When an argument Is passed to a procedure by name, any
changes made to the value of the formal parameter In the
procedure also changes the actual parameter as If it, instead of the dummy, appeared In the procedure body.
Passing an array or a Siring argument by name instead of
value saves memory space and allows the procedure to
treat the argument as a global variable.

At run time, AlGOTS provides I/O processing , storage
management, and debugging facilities. ALGOTS consists
of a sharable high segment of 11 K words and a low segment of at least 2K words for each program depending on
object program size, library routines used, and heap and
stack sizes. The object system provides a checking mode
for selective testing of array subscript bounds.

ALGOL supports recursive procedures that can cali themselves directly or Indirectly to a depth limited only by the
user's available memory space.

The object-time system Includes a library of routines that
can be Incorporated Into a user's program,lncludlng:
• A set of mathematical functions of both slngle- and double-precision
• Maxima and minima functions
• String manipulation routines
• BIt field manipulation routines
• FORTRAN subprogram Interface routines

Complier and System Features
The ALGOL complier reports all source program errors on
the user's terminal or on a listing device. The AlGOl-20
complier adds these extensions to AlGOL-60:
• long real data type equivalent to FORTRAN's doubleprecision data type for more accurate real computations
• External procedure can be complied Independently of
main program
• Convenience in loop Implementation with WHilE and
abbreviated FOR statements
• Programmer can manipulate strings of various-sized
bytes and can Individually manipulate the bytes within a
string through byte subscripting
• Integer remaInder functIon
• Delimiter words can be represented in either reserved
word format or as nonreserved words
• Conslants of data type real can be expressed as an Integer part or as a decimal part only

The runtime facilities Include:
• I/O with directory and nondlrectory devices In both
ASCII and binary modes. Up to sixteen Internal logic
channels plus default terminal 1/0 channels are available.
• Storage management 01 the heap and stack enables the
program to borrow a temporary buffer for 1/0, OWN
arrays, and dynamically created byte strings. It also provIdes memory expansion when needed.
• The ALGOL dynamic debugger allows interruption of
program execution, setting and clearing of breakpOints,
examination and alteration of ALGOL variables that are
In scope, examination of various system parameters,
automatic typing of ALGOL variables after a breakpoint,
examination of the code generated, and continued program execution both from a hall and from an appropriate label.

OWN Variables
Special Integer, real, tong reat, Boolean, and string variables called OWN variables have these properties:
• They follow the normal scope rules within a block
• When control passes outsIde the block, the values are
retaIned and stili available when the block Is reentered
• Their values are Initialized to zero, false, or null

BASIC-PLUS-2
Although BASIC-PlUS-2 is an ideal language for novice
programmers who need a fast, easy way to solve problems, it Is also a powerful, efficient language suitable for
sophlsflcated applications.

OWN variables are vatuable In large-array work Inside procedures because the array doesn't have to be Initialized
every time It Is referred to. Arrays defined and used Inside
procedures are comparable to subroutines in other languages, but they can be dynamically defined and
red efined.

BAS1C-PlUS-2 retains Dartmouth BASIC's simplicity and
ease of use. It adds many features and greatly enhances
performance 10 accommodate a wide range of applications. The BASIC-PlUS-2 complier produces fast-running
programs, yet Its Immediate mode retains Ihe advantages
of the much slower BASIC Interpreters.

Switches
Switches provide the function of the CASE statement program control jumps to various locations depending on
the value of an expressIon. Switches automatically detect
when the evaluated expression Is out of range.

BASIC-PlUS-2 uses features of the TOPS-20 operating
system to provide Immediate mode and complle-and-go
execution. The user can also save complied processes as
direCtly executable modules. BASIC-PlUS-2 features Include:

String Constants
String constants enable the user to refer to strings of ASCII
characters within a program by using a variable name. The

8-5

• Immediate "desk calculator"/debug mode
• Ability to save compilations
• Error dlagnosllcs and .program-controlled error-handling routines
• Subprogram capabilities to help structure programs
• IF-THEN-ELSE, UNLESS, WHILE, and UNTIL elim inate
most 01 the need for GOTO statements
• Block formatting with unlimited slatement length, multiline statements, and multlstatementlines
• Variable names 01 up to 30 characters make programs
more readable and easier to document
• Full matrix manipulation and arithmetic
• Powerful string-handling functions
• Arrays stored In flies , yet can be accessed the same as
In-memory arrays

Record Input/Output
Three methods for performing record I/O operations are
provided: formatted ASCII 110, 110 to virtual memory arrays, and block 110 .
Record 1/ 0 permits the user program to have complete
control of I/O operations. Properly used , It Is the most
flexible and efficient technique of data transfer available
under BASIC-PLUS-2.
Language extensions efficiently handle records composed
of fixed-length fields. Block I/O offers great flexlbmly and
performance for Input and output device transfers . For
example:
• GET and PUT statements Initiate I/O operations for d isk
and magnellc tape, and read and write sequential data
blocks.
• For relallve disk files, the programmer can have complete random access to the file by specifying a record
number In the GET, PUT, or FIND statement.
• For Indexed disk Illes, the programmer can access records by multiple key values.

• Other data file structures, Including ASCII text Illes and
sequential, random, and mull1key indexed record flies
• Formatting facilities for output and reports
File Capability
BASIC-PLUS-2 gives users high-speed , online access to
disk files. Flies can be created , updated , extended, and
deleted under program control.

• Programmers use MAP and MOVE statements to map
an 110 buffer. The MAP statement defines the format of
a record when that format can be specified at compile
time. If the lormat cannot be specified at compile time,
the MOVE statement can be used to dynamically access
the data in a record.

Any number of programs can simultaneously read data
from the same file, but only one write operation can occur
at a time. Multiple updates are handled safely through the
UPDATE feature. UPDATE locks a disk record from other
programs while one program Is updating II. so all programs access current, valid files. Programs can be written
to recover cleanly from failed attempts to open or access
files.

• A set of numeric/ string conversion functions permits
optimum packing of number fields, thereby saving
space In the record.
• Programmers use formatted or stream ASCII 110 to handle character strIngs of indeterminate length. System
fecillties handle the blOCking and unblock ing of formatted ASCII flies.

Virtual Memory Arrays
Many applications need to address and update random
record s on a disk file. Other applications mIght require
more memory for data storage than Is econom ically feasible. BASIC-PLUS-2 fills both of these requirements with
virtual arrays, a Simple, random access Iiletype.

Data Format, and Operation,
Programmers can manipulate string, Integer numeric, or
floating-point numeric data.
String variables are sequences of ASCII characters thai
are treated as units. Programmers can define string constants and string variables, Including subscripted variables. In additIon , relational operators can be applied to
string operands to compare and Indicate alphabetic
(ASCII) sequence. UsIng the CHANGE statemenl, lndlvldual string characters can be converted to their equivalent
ASCII code In decimal, and vice versa.

With the virtual memory array faCility, programmers can
specify that a particular data matrix Is not to be stored in
the computer memory, but on disk. Data, stored on disks
that are external to the user program, can be retrieved by
name at a later session. Items within the file are Ind ividuallyaddressable.
Using the virtual memory array facility, programs can operate on data structures that are too large to be wholly In
memory. The disk file system Is used for storing data
arrays, and only portions of these files are maintained in
main memory at any given lime.

A variety of string functions enables programmers to concatenete two strings, access part of a string, determine the
number 01 characters In a strlng , search for substrings,
convert strings to compact storage formats, and define
new strIng functions. Character strings can be any length,
limited only by available memory.

With virtual data storage, programs can reference any eiement of one or more matrices within the files, no matter
where in the file the element resIdes. Random access allows programmers nonsequential referencing of the data
for use In any BASIC statement. Virtual memory matrix
elements are read Into memory automatically by the system.

String arrays further enhance the usefulness of string variables. An entire list of alphabetic data can be Input, processed , and output with only two statements.
Usually, all variable and constant numeric values specified
In a BASIC-PLUS-2 program are stored Internally as
floating-point numbers. If operatfons such as counting , Indexing , and subscripting deal with Integer numbers, slg-

Virtual memory arrays are stored as unformatted bInary
data. This means that no 110 conversion is performed
when storing or retrieving elements In these arrays.

8·6

Subprograms or programs connected by a CHAIN share
data through COMMON statements.

nlflcant economies In storage space can be achieved by
using the Integer data type. The Integer data type requires
only one word of storage per value. Integer arithmetic Is
significantly laster than Iloating-point arithmetic.

The ON ERROR GOTO statement allows programmers to
write subroulfnes to handle error conditions normally considered fatal. The program. can test a system variable to
determine which error occurred, and can examine another
system variable to determine the line number at which the
error occurred. The action taken depends on the error
and, If desired, on the line number of the error. For example, a program user might specify a nonexistent data lIIe
lor Input to the program. The error-handling routine could
print a message such as "no such lIIe, try again," and then
return execullon to the line that requests the data lIIe
name.

Single- or double-precision, floating-point numeric operatloos are the default numeric type. Single-precision Iloatlng-point numbers occupy one word 01 storage In memory,
and double-precision numbers occupy two.
Programmers working with Iloating-point numbers can
Increase accuracy of operations Involving fractional numbers by using the string arithmetic lunctlons or the scaled
arithmetic feature,
Programmers can perform arithmetic operations using a
mix of integer and floating-point numbers. II both operands 01 an arithmetic operation are either explicitly Integer
or explicitly lIoatlng-polnt, the system automatically generates Integer or floating-point results. II one operand Is an
Integer and another Is floating-point, the system converts
the Integer to a floating-point representation and generates a lIoating-polnt result. II one operand Is an Integer
and the other operand is a constant that can be Interpreted
either as a floating-point number or an integer, the system
generates an Integer result. Programmers can explicitly
Impose the formats, thereby controlling the result of the
operation,

The SLEEP and WAIT statements allow program suspension, either for a specified lime Interval or until Input from a
terminal Is received.
Debugging Tools
Dynamic debugging tools maximize program debugging
efficiency by minimizing the need to rerun programs. Programs can be Interrupted at any point to check. correct,
and then resume operation. The most uselul of these tools
are Immediate mode statement execullon, the STOP statement, and the CONTINUE command.
Using Immediate mode, programmers enter a statement
without assigning a program line number. and then immediately execute that statement. A programmed and an
immediate mode statement are dislfngulshed solely by the
presence or absence of a line number.

... trlx Manipulation
Arrays are Indexed variables containing data of anyone
type - integer, floaling-polnt, or string, Arrays can have
one or two dimensions, and the number of elements In
each dimension Is Implicitly or explicitly declared by the
programmer. The number and size of an array's
dimensions are explicitly defined with DIM, MAP, or COMMON statements, They are Implicitly defined by declaring
a subscripted variable. The size of an array Is limited only
by available memory.

Immediate mode is also useful for performing simple
calculations that occur too Infrequenlly to warrant being
programmed.
When debugging, programmers can use STOP statements
to create executable sections of their program. Upon execution, a STOP statement halts the program and displays a
message Indicating where the program was halted. The
programmer can then use Immediate mode to examine
and lor change data values. or to add, to delete. or to modIfy tines. CONTINUE or GOTO statements are used to continue program execution.

Programmers can alter the number of elements in each
and the number of columns In the matrix and can
Input. print, add, multJply, transpose, Invert. or take the
determinant of entire dala matrices In a single operation.
(OW

Conditional Statements and Program Segmentation
BASIC-PlUS-2 extends the BASIC language by Including
several additional statements for easier logic flow and
function definitions. The IF-THEN-ElSE, WHilE, UNTil,
GOSUB, function definition , and CAll statements provide
a variety of loop controls, as well as function and procedure subprogram capabllJtles. The programmer can use
multiline statements, multistatement lines, and the subroutine features 10 write structured programs, without GOTO
statements.

APL
Two levels of this popular language are available, and both
are full APl Implementations with significant extensions.
The basic version suits users who do not require the IIle
1/ 0 or the advanced APllunctions. The extended version
of APl, APl-SF, has all of the features of the basic version
plus advanced features that substanllally Increase its useful range of applications. Both feature:
• Full Implementation with significant extensions
• Fastexecutlon
• System functions/ variables
• User-definable error trapping
• Error analysis and recovery
• Support of highly Interactive applications
• Double-precision arithmetic

The CAll statement accesses external subprograms. Programs can comprise several modular segments, each of
which can be complied separately to speed program
development.
The CHAIN statement translers control from the current
program to a program stored In a file. CHAIN loads a program from the file, complies It If necessary, and starts its
execulfon from the beginning or from any line number.

8-7

• Integrated debugging features
• Workspace Interchange features or capabilities
APL-SF enables the user to obtain canonical string
representations, to create local functions, to erase and
classify names from a workspace, and to perform various
file 1/ 0 operatIons Including ENQ/ DEQ. APL-SF features;
• System variables with which the programmer can set
tolerances, Index origIns, and store accounting Information
• File 1/0 that makes It easy to structure program data and
Interchange dala flies between other DECSYSTEM-20
languages such as FORTRAN and COBOL
• System commands with which the programmer can redirect termlnallnpul and output to any file
• A function that can solve linear equations, take the Inverse of a matrix, or solve an overdetermined set 01
linear equations using a least-squares fit
• A function that converts numeric data to a character
string and enables the programmer to write user-defined functions that perform special output formattIng
and functIon editing
• A function that efficiently finds the Indices In a vector for
which a particular 800lean expression Is true
• A funct ion that executes a character as an APL
statement
• A convenient and efficient mechanism for formatting
output data; for example, an entire table with associated
text can be formatted In a single operation, or a large
matrix can be formatted with alphanumerics
APL uses one of the most concise, consistent, and powerful character sets ever devised. APL Is especially suited for
handling array-structured alphanumeric data. It Is also
usad as a general data processing language and a mathematical tool.

System Commands, Functions, and Variables
Programmers can change system parameters, determine
hardware or operational characterlstlcs, and modify workspace parameters through system commands, system
functions, and system variables. System commands control the operational environment In whIch an APL session
Is conducted by allowing programmers to examine or
change the state 01 the system. System functions and variables are used to communicate with the APL system to
change user workspace characteristics and to report sta·
tistlcs about the workspace and the APL system.
Statements
There are two types of statements In APL programs; assignment and branch . Asslgoment statements Include calculation and Input/output operations. Branch statements
are used to restart a lunctlon or to handle the transfer of
control from one part of a program to another. Branch
statements are relevant only to programmer-defined
functions.
An APL statement can contain:
• Identifiers
• Constants
• APL primitIve functIons
• User-defined functIons
APL Statement Execution
APL language statements operate In either of two modes;
• Immediate or execution mode - In this desk-calculator
mode. APL slatements and expressions entered by the
user are executed Immediately
• Functfon-de/inition mode - In this mode, APL programs and functions are developed, edited , named , and
saved for later use
Programmers can shllt from one mode to the other. The
syntax of the APL language Is Identical In both modes.

APL allows programmer-defined functions and primitive
language functions to be expressed with the same syntax.
Thus, programmers can expand the capabilities 01 the language to handle the requirements of any application.
Data Structures
APL supports a variety of numeriC and character data
structures. They are:
• Scalars, which are a single numeric or character value
with no dimensions
• Vectors or lists, which are one-dlmenslonal arrays or
character strings con~lsting of any number of values
• Matrices or tables, which are two-dimensIonal arrays
consIsting of rows and columns
• Arrays with three or more dimensions - the maximum
number 01 dimensions and the maximum size of an array are limited only by the size of the workspace
Interacting with APL
Programn)ers interact with APL using a hardcopy or video
terminal. DIGITAL's LA37 and LA120 hardcopy terminals
Include an APLIASCIl dual-character set. On other terminals, keyboard mnemonics can represent special APL
characters.

8·8

Debuggi ng Tools
Function execution Is suspended If en error occurs or If a
stop vector Is set. When execution Is suspended, the program displays the name of the suspended function and the
line number of the statemant that would have been executed next or that was being executed. APl then awaits Input
In Immed iate mode. Programmars can perform any other
APl operations at this time. The programmer can resume
execution after fixing the problem and can observe function nesting.
Programs can also automatically display intermediate
results of function execution. As a program-tracing aid,
the values computed by one or more function statements
can be output each lime those statements are executed.
Fu nction execution can be suspended from within the
function Itself. A stop control vector with a syntax similar to
that of the trace vector suspends function execution Just
before execution of one or more specified statements.

curs, a particular APl expression be executed. Within
that expression, the error can be analyzed and remedial
action taken.
Error-trapping features enable computar-asslsted instruction applications. A programmer can, for example, write a
program that lets a student write a prOblem solution. The
controlling program can Intercept any student error.
Conversion Package
A complete package Is avaJ1able to convert non-DIGITAL
APl workspaces and data files Into APl-SF workspaces
and data files. The package code Is mostly APl and Is
easily adaptable for use with other APl systems. It Is written according to the workspace Interchange convention
. adopted by the SIGPlAN Techn ical Committee on APl
(STAPl) of the Association lor Computing Mach inery
(ACM).

Workspaces
An APl workspace is a buffer In the programmer's memory area that stores the functions, variables, values, and
temporary results obtained whlla executing APL state-ments. Using APl system commands, workspaces can be
saved, loaded , and erased. Workspaces are stored as
DECSYSTEM-20 disk fUes and can be manipulated as
such.

BLlSS-36
BUSS-36 is DIGITAL's Implementation language for software development. BLISS Is an optimizing , high-level systems-Implementation language lor the DECSYSTEM-20. It
Is desIgned for building compliers, utJlltles, and operallng
system software, and encourages the writing of highly
structured , easily maintained programs.
BLISS has the features 01 a modern, structured high-level
language combined with the flexibility of an assembly language. BUSS can help systems programmers be more
productive, shorten project development time, and lower
maintenance cost.

Through the file I/O facilities of APl-SF, a user can convert
an APl workspace to ASCII format, and then edit It with
any DIGITAL-supplied editor.
File Organization
The APl-SF file system allows access to data and program
files on a variety of system devices. The lIIe system, Imptemented as an Integral part of the APllanguage, provides
an interface to the TOPS-20 operating system.

The key features 01 BLISS are:
• State-ol-the-art optim ization technique to generate
highly optimized programs
• A lull set 01 structured programming constructs IncludIng IF-THEN-ElSE, CASE, DO-WHilE, SELECT, and
DECR statements
• Sophisticated macro processing capabilities
• Access to machine-dependent features Includ i ng
PSECTS, hardware regi sters, and machine Instructions
(Including UUO and JSYS)
• A linkage declaration that supports user-selected register conventions. Users can rebuild the object-time system to support nonstandard regIster conventions

The APl Ille system support Is provided by system functions for assigning, closing, synchronizing, and renaming
llIas, and by file functions for Input and output operations
on ASCII data, APl data objects, or arbitrary binary data In
either sequential- or random-access modes.
APl supports ASCII sequential- and random -access flies.
ASCII sequential data fUes can be read and written sequentially by any TOPS-20 language processor (e.g., BASIC--PLUS-2, FOATRAN, MACAO). APl can treat random
access flies as random access memory. Programmers can
access any word in the file directly by specifyIng the
Individual word or value to be read or written . APl arrays
of any shape or size can be read from or written to APl
files either sequentially or randomly by component (I.e.,
record) number.

• Precompiled source libraries similar to MONSYM
Compiling
The complier can display a listing of errors and warning
flags on the programmer's terminal or can generate alisting with the errors and lIags embedded. listings can be
printed as needed, and most syntax errors are labelled as
such.

Error Analysis and Recovery
Instead of stopping execution, APl-SF error analysis and
recovery permit the program to take remedial action.

Debugging
An interactive symbolic debugger supporting BLISS-style
expression evaluation Is used .

There are two ways to trap errors:
• The programmer can execute an expression suspected
of causing an error, then test whether an error occurred.
• The programmer can specify that whenever an error oc-

File Organization
BLISS can access any file organization .
8-9

Compatibility with Other Languages
BLISS Is not Intended to replace the other high-level languages such as COBOL, FORTRAN, or BASIC; Instead. It
complements them. Programs written in other languages,
except BASIC-PLUS-2, can call BLISS routines through
the standard operating system calJlng sequence. BLISS
programs can call routines written In a variety of other
languages, and they use several linkage conventions.

CPL
Conversational Programming Language (CPL) is a PL/ I
subset interpreter. It Is well documented, easy to learn,
and a subset of ANSI-1976 PlIl .
At the user's option, statements are executed Immediately
or saved for deferred execution. A beginning programmer
can start by executing simple computational statements
and proceed to building programs.
Since CPL Is an Interpreter, a user can track programs
very closely. Debugging features Include source-level
breakpoints and program modificatIon.
CPL includes:
• ANSI PlIi statements - ALLOCATE, ASSIGNMENT,
BEGIN. CALL, CLOSE, DECLARE, DEFAULT, DELETE,
DO, END, FORMAT, FREE, GET, GOTO, IF, NULL, ON,
OPEN, PROCEDURE, PUT, READ, RETURN. REVERT,
SIGNAL, STOP, and WRITE
• Data types - FIXED, FLOAT, CHARACTER, CHARAC_
TER-VARYING, BIT. BIT-VARYING , POINTER, and arrays of these types
• Storage classes - AUTOMATIC , STATIC, CONTROLLED, and BASED
• Recursive procedure support
• Almost all ANSI PLI I arithmetic, mathematical, string_
handling, array, and storage control built-In functions
• STRING, SUBSTR, and UNSPEC pseudovarlables
Immediate Mode
The CPLlmmediate or desk-calculator mode Is Integrated

InlO the system so that the user can easJly move between
programming and calculating.
Almost any CPL PlI I language statement can be typed
without a line number for immediate mode execution. A
user can perform simple computations to get immediate
answers, and can assIgn Intermediate results to variables
and use the varIables In further computations. Immediate
mode Is thus useful for debugging.
Program Creation
Programmers can creale CPL programs wlthout using an
edllor or utl/iry. Program statements are ryped to CPl;
InsertIons, changes, or deletions are done easily.
CPl provides automatIc, immedIate syntax checkIng 01
statements. If there Is an error, CPl tells where the error
Occurred. The USer then can correct the statement and
continue. ThIs avoIds waiting for a compilation to provide a
JIst 01 errors.
Programs created usIng an editor or file manipulation facliity are checked' automatically when loaded Inlo CPt.
Any erroneous statement will be listed with an error
message thai indlcales the problem.
Oebugglng
CPL Is the only PlI t language processor available that
provides true source-level program debugging. To debug
a program, a programmer can:
• load the program.
• Set breakpoints on any statement.
• Execute the program.
• Use CPL statements In immediate mode to Isolate problems when the program stops on an error, a breakpoint,
or al programmer command. Variables can be examIned or changed. 1/ 0 can be done. Newvariables can be
created to store Intermediate resurts.
• Make source modilicalions to the program, such as add,
delete, or modlly statements, and set or clear breakpoInts.
• Continue execution aiter the current halt in execution.

9
Data Management
and
Application Products

In addition to the standard file management facilities described In
Section 4, TOPS-20 has optional data management and application
products.
DBMS Is a CODASYL-compliant database management system with
which users can organize and maintain data in customized databases,
and rapidly and conveniently access that data. IOL Is an Interactive
query language for information retrieval and report writing. IOL can
access DBMS files. SORT IMERGE is a TOPS-20 sort utility that
operates by Ilself or with COBOL or FORTRAN programs to reorder the
records of files Into new sequences or to merge sorted files into a
single, sorted file. TRAFFIC-20 Is a collection of CAT screen-formatting
and program-Io-program communications subroutines useful In
writing online COBOL transaction processing applications.
Two application products, COGO-20 and PCS-20, are also available.
COGO-20 includes a geometriC language for solving problems in plane
coordinate geometry. PCS-20 is a project control system Ihat analyzes
critical path or procedure networks and generates a number of
resource, cost, and critical path reports.

Data Manipulation Proce ••
Database records can be referred to via data manipulation
statements Included In COBOL or FORTRAN application
programs. These statements are used to store, modify,
and delete fields and records that are 01 specific interest to
an authorized application user. Records can be Inserted
and removed within structural relaUonshlps, and can be
directly accessed by symbolic keys or by movement
through structural relationsh ips.

The data management products detailed In this section
are:
• DBMS - a CODASVl database management system
• lal - an Interactive query language for information retrieval and report writing
• SORT/ MERGE - a sorting and merging utility for
TOPS-20 flies
• TRAFFIC-20 - a collection of screen-formatting and
program-ta-program communications subroutines for
COBOL programs

DBMS Modules
TOPS-20 DBMS modules Include the Data Oeflnltlon language, Data Manipulation language, and Database Control System.

The opllonal appllcallon products discussed are:
• COGO-20 - a tool lor solving problems In plane coordinate geometry using a geometric language
• PCS-20 - a project control system that analyzes critical
path or procedure networks

The Data Definition Language (DOL) equips the database
administer to centrally define the 10glcJlI and physical
characteristics of the database files and database records.
By controlling the placement of records on the physical
slorage medium, the administrator can assure both data
security and high-speed data retrieval.

The comprehensive data menagement system that is part
of TOPS-20 and Included with all DECSVSTEM-20s Is discussed In Section 4 of this technical summary under the
headline The File System. Access to data files from various
programming languages is described In Section 8.

Records can be grouped logically In "sets", which are used
to model the real-world relationships among objects . Instead of storing extra data about relationships, DBMS-20
links related record s In log ical chains.
This thrust toward effective real-world modeling Is carried
a step further In transaction definitions. A transaction definition Is an Integrated serles of manipulations performed
against the database. A transaction defines the conteltt of
these Interactions, allowing the user to perform a series of
data manipulations as a slng le,lntegrated operation .

DBMS
DBMS Is an optional TOPS-20 CODASYl-compliant database management system that lets users organize and
maintain data In customized databases and provides rapid
and convenient access to the data.
DBMS integrates relaled processes and data structures. It
Is used when trad itional file management techniques
woutd be dllllcult, costly, Inadequate, and / or prone to error. DBMS features :

The database delinltlons reside In a central location In the
SCHEMA, and can be accessed by user programs through
the SUBSCHEMA. A SUBSCHEMA Is a subset of the
SCHEMA that Is defined by the administrator to satisfy the
needs of related groups of programs. By restricting the
scope of the SUBSCHEMA. the administrator can prevent
certain classes of users Irom accessing portions of the
database, from the level of flies down to the level of data
Items. This feature provides one 01 the Inherent security
checks of DBMS-20.

• COBOL and FORTRAN interfaces
• English-language Interface for Inquiry and report generaUon through the lal package discussed below
• Easy SCHEMA/ SUBSCHEMA definition and update
• Full journallng and database recovery capability
• Protection against unauthorized database access with
centralized control of privacy
• High throughput
• Temporary work areas for use during development to
protect database Integrity

The Data ManIpulation Language (DML) performs the database retrieval and update. The programmer Includes
OMl statements in a COBOL or FORTRAN program . COBOL and FORTRAN are called the host languages for
DML.

COOASYL Compliance
DBMS provides software to define, access, and maintain
data in the network structures of an Integrated database.
DBMS Is based on the CODASVl Database Task Group
Report of Aprlt 1971 .

The IIrst DMl statement In a program Is the INVOKE statement, wh ich provides the program with the definitions
from the SUBSCHEMA, In a form suitable for the host
complier. No further data declarations are needed because the centrally defined database structures are
mapped directly Into the host program.

Data Description Procest
Data structures can be established either In a hierarchical
form (a trae) or in networks with multilevel relationships.
Relallonshlps can exist within or between files with no
Jilted limit on the length of chains. The TOPS-20 file system
Is used to construct data base areas. The number of relalionshlps Involving any record and the size of the record Is
normaUy limited only by the design constraints of the application.

DBMS-20 provides multithreaded simultaneous update.
Many users can access the database at the same time.
Each program Is protected by a system of locks that are
controlled In the Schema. The database administrator can
grant exclusive control to one program, or distribute It
among many programs, When a large number 01 programs are using the database, each one locks the resources It Is using until II completes Its transacllon . The

9-1

protective locks can be placed on areas (files) being used,
or on the specific database page.
Two typical DML verbs are FIND and STORE. In DBMS-20,
there are six ways to find a record: by traversIng a set, by
hashing a data Item , by sorted order, by direct address, by
relative address, or by current program context.
When a record is read from disk, DBMS-20 can also read
In other database pages containing related records. This
operation, called clustering, requires only a single disk access for the entire page cluster.
The STORE statement, In addition to placing the record on
the database, automatically performs a number of operations. In accordance with the specifications of the Schema,
a record can be stored next to its logical group, or can be
distributed randomly across the database. The Schema
can specIfy how many records to place on a slngte page,
or how many pages to leave between records. The STORE
operation can automatically choose an appropriate set
and link the record to !t lmmediately.
An important, but largely Invisible component of DBMS·
20, Is the journal, which is a record of everything that has
happened to the database. When using the journal , a program can recover from any kind of error that affects the
database - either automatically or under program control, the database Is restored to the state it was before the
c urrent transaction began. The journal helps assure the
conslstency,lntegrlty, and reliability of the database.

port-generating commands. IOl can access TOPS-20 files
and Interface to DBMS to provide a powerful, fully Integra·
ted database management system.
IOl features:
• Multiple Input flies (DBMS, ISAM, sequential)
• Extensive record selection
• Sorting
• Conditional processing - ANDI OR conditions can be
strung together; parentheses can be nested nIne deep
• Bullt·ln summary statements
• Complete report-formatting capabilities InCluding multl·
pie across labels and speclallorms
• MultIple reports - up to nIne, standard , and expand·
able
• Flies can be output In original or new format
• Matrix reporting by manipulation 01 summar ies or
Individual Items
• Powerful computation capabilities
• Built-In summary statements for tallies, totals, and aver·
ages
• File-updating capability
• Dictionary presorting 01 liIe, record, and Item Informa·
tion, Including printing of column titles and pictures
• Default automatic formatting of reports, Including field
alignment, dates, paging, and columns
• Interactive or batch modes of operation
• Exits to user-written modules

Datebase Control System (DBCS) that is a runti me Inter·
face between a COBOL or FORTRAN program and the
TOPS-20 operating system. The DBCS exists In a specific
module withIn the COBOL object-time system (UBOl) and
the FORTRAN object-time system (FOROTS). Failed DML
updates are recovered via the journaling faCility.

Traditionally, data manipulation and reporting has been
tell to programs written in COBOL, FORTRAN, or assembly language. This method Incurs high programming costs
and delays In obtaining report Information. tOl, however,
is an Inquiry system that can quickly extract, summarl1e,
reorganIze, report, and copy file Information . Table 9-1
Illustrates the use of IOl Ad Hoc Inquiry and reporting.

DBMS Utilities
The DBMS utilities help the database manager run and
maintaIn the database. The utilities Include:
• DBMEND - for repairing the database using the Journal. DBMEND can restore the database after a system
software or hardware failure, or a user error.

Interactive Mode
In Interactive mode, IOl operates under control of term inal
front-end modules, so that terminal users can:
• Write, store, retrieve, or change queries
• Deline and Interrogate dictIonaries
• Deline dictionaries reflectIng SCHEMA flies for DBMS
databases
• Browse or update sequential or Indexed sequentlal In·
putliles

• DBINFO - to generate a variety reports about the
structure and contents of the database, Including maps
and dictionaries from the Schema. Users can also obtain
data dumps of single pages, single sets, sIngle records,
or any larger portion 01 the database.
• STATS - to generate complete statistics about the perlormance of the database. These statistics, relating to
buffer management, disk 110, lock performance, and
DMl runtime, allow the database administrator to evaluate the database design and fine-Iune It for maximum
performance. ST ATS can be called by a database program.

• Create sequential output files
• Accept raw data Input
• Operate other IOl system modules
• Display snapshot reports on the terminal
Deferred Mode
In deferred mode the IOl system provIdes powttrlut
retrieval selection, report formatting, sorting , computation,
summarization, and data file writing capabilities. Up to
three Input files can be read. The Input files can be DBMS
database Illes, sequential Illes, or Indexed sequential flies.
They can contain flxed- or variable-length records, and
one or more record types. Input data flies are queried In

IQL
The optional Interactive Ouery language (IOL) Is used with
TOPS·20 lor Information retrieval and report wrIting. It
takes requests written In English-like formats, reads one
or more Input files, and processes the data according to
the request. IOl queries are groups of easily written, reo

9·2

Table 9-1

tQl Ad Hoc Reporting

The Query:
OPEN CUSTOMERS
RPTHEAD " ANALYSIS OF// PRICE CHANGE/II MPACT"$
IF CSTATE EO "N H","VT", "MA", "M E" THEN GO TO
10 ELSE GO TO NR$
10 COMPUTE XSAlES :CYSAlES·l .l 0$
COMPUTE XOIFF - XSAlES-CYSAlES$
PICTU RE XSAlES: " ZZZZ.99",XDIFF -"ZZZZ.OO"$
TOTAL CYSAlES $ TOTAL XSALES $ TOTAL XDIFF$
PRINT CNAME,1,CYSAlES,XSAlES,XDIFF,CSTATE $
The Report:
05-01-8 1

ANALYSIS OF
PRICE CHANGE
IMPACT

PAGE 1

CUSTOMER
NAM E

V-T-D
PURCHASES

XSAlES

XDIFF

MANFREDINI VIOLIN CO.
GlOBAlEX
LAKESIDE HOMES INC.
FARFtElD MOTORS
HUBERT Oil COMPANY
BEE DRill SERVICE
INVESTMENT INC .
ENERGY RESOURCES INC
GEO BANK FISHERIES
MERRIMACK VAllEY SALES
APPLE ORCHARD INC.
GIRAFICS ADVERTISING

$1 ,233.67
$2,500.00
$1 .211.00
$9,000
$600.00
$1 ,000.00
$364.75
$8,000.00
$9,164.00
$6,000.00
$671.00
$5,115.50

1357.03
2750.00
1332.10
9900.00
660.00
1100.00
401.22
88000.00
10080.40
6600.00
738.10
5627.05

123.36
250.00
121 .10
900.00
60.00
100.00
36.47
800.00
916.40
600.00
67.10
511 .55

FINAL SUMMARIES
Y-T-D
XSAlES
XDIFF

TOTAL:
TOTAl:
TOTAL:

$44,859.92
49,345.90
4,485.88

END QUERY EXECUTION

DBMS File.
lal accesses data files under control of a data dictionary
that describes the format of the file and the location, the
default display pictures, and the column titles of each Item
In the data record(s). For DBMS databases the dictionary
also Includes pertinent Information about record names,
set names, and area names. Password protection can be
applied to Individual data items or groups of Items.

their original format and can be In SIXBIT or ASCII mode.
All standard data item types are permitted. Only sequential or Indexed sequential Input files can be updated;
DBMS databases cannot. Sequential output files can be
generated that either mirror the format of the primary Input data file or assume a new format as specified by the
query.
Queries can be stored In text flies or In executable form for
later reuse.

To use DBMS database flies, the SCHEMA file must be
present. Privacy locks provide additional security for
DBMS databases. lal's queries opera'e In stages delimited by SORT statements. lal can sort data Items or calculated fields In ascend ing or descending order.

IQl St.tements
An tal selection statement can combine many conditional
tests con nected by AND and OR logIcal operators and
clarifi ed with parentheses. An lal computational statement can Include addition, subtraction, multiplication, and
division with parentheses. Data Item breaks can be used to
con trol built-In summary statements for tally, total , average, maximum, and minimum calculation. A random num·
ber variable Is built In.

Report Formatting
IOl has automatic and custom report formatting. Users
specify data item placement in reports. Both multiple print
lines per Input data record and multiple Input data records
9-3

•

per print line are permitted. Special-form reports such as
mailing labels and checks can be produced easily. Up to
99 multiple reports can be generated at onetime.

• Alignment and spiral functions
• Maintaining compatlblllty with the previous COGO so
that existing Input can be used
• Outputting Information generated by COGO

SORT/MERGE
The optional TOPS-20 SORT/MERGE utility operates by
Itself or with COBOL or FORTRAN programs. The user
specifies parameters for the sort sequence and the collatIng sequence.

PCS-20
PCS-20 Is an optional TOPS-20 Project Control System
that analyzes critical path or procedure networks and generates a number of resource, cost, and critical path reports.

SORT/MERGE reorders the records of EBCDIC files,
ASCII Illes, SIXBIT flies, and binary files produced by COBOL or FORTRAN.

PCS-20 can process data for any critical path network developed in an IJ/CPM, or precedence technique. The
fixed-format input can be entered on a variety of media.
The system Includes a terminal-oriented editor for Input
from a CRT or hardcopy terminal.

SOAT / MERGE automatically controls the use and allocalion of disk workspace and memory workspace, although
the user can specify memory limits. SORT/MERGE provides error dlagnosllcs and statistics, upon completion.

PCS-20 has the following features.

MERGE combines sorted flies into a single sorted file. This
function can be used alone, with COBOL, or with FORTRAN.

• The time required to perform a work Item can be expressed in seven different time units.
• Seven different days can be designated as the starting
day of the work week associated with each work Item.
• The work week of each work item can be one to seven
days.

TRAFFIC-20
Transaction Routing and Forms Filling In COBOL
(TAAFFIC-20) Is a collection of CRT screen-formatting and
program-la-program communications subroutines available to COBOL programs. TRAFFIC-20 Is optional on
DECSYSTEM-20s.

• Anyone of three distinct calendars can be used for each
work item.
• The actuel dates can be specified for each work item.
• One of five types of "scheduled" dates can be specified
for the start and completion of each work Item.

TAAFFIC-20 Includes a set of screen-formatting routines,
a set of transaction-routing routines, and a stand alone
utility program for defining and saving CRT screen format
descriptions. With the screen-formatting routines a COBOL program can send formatted CRT displays to, and
receive data messages from terminals. The transactlonroullng routines equip a COBOL program to send and to
receive data packets to and from another cooperating COBOL program.

• Two "early" and two "late" dates can be computed for
each work item.
• Two types of duration can be specified for each work
Item.
• Two types of "percent complete" can be specified for
each work Item.
• Two kinds of "float" can be computed for each work
item.
• Three different kinds of codes can be specified to be
associated with each work item.
• Three kinds of costs can be specified for each work
Item.
• An IJ/ CPM or a precedence network can be accepted
lor processing.

COGO-20
COGO-20 Is an optional TOPS-20 tool for solving problems In plane coordinate geometry. II Includes a geometric
language. COGO-20 Is used In such tasks as land surveying, highway des ign, right-of-way surveys, bridge
geometry, end subdivision work.

• An IJ/CPM network Is Internally converted Into a precedence network for processing.

The user works directly with the COGO language, which
consists of common engineering terms. No computer experience Is required to use It. Using the commands, problem definitions can be stored In a file and executed at a
later time, or can be entered Interactively on a terminal
keyboard.

• Three different relationships can be specified between
any two work Items when using precedence Input.
• loops are detected and Identified.
• A time delay can be specrfied that becomes an Intrinsic
part of the relationship between two work Items.
• All network calculations are based prImarily on three
calculation dates.

COGO has commands for:
• Starting and ending a COGO Job or changing the 1/ 0
device

• The specification of 240 "milestones" Is possible.
• Fourteen different types of output reports can be produced on request:
lour different kind of system runs can be specified ,
and
a network can extend over a period of 2,911 calendar days, that Is, slightly less than eight years.

• Maintaining tables (lists of related points such as road
alignments or property lines)
• Intersecting existing lines or figures to calculate a new
point
• Calculating and/or storing one or more points
• "locating" In traverse work

9-4

10
Communication

A range of communications software expands the DECSYSTEM·20's
capabilities tor interactive computing and distributed processing.
Distributed processing software, remote Job entry stations. IBM
protocol emulators, and a document transmission package for word
processing equip TOPS-20 to communicate with other DIGITAL
computer systems and with IBM mainframe computers and remote job
entry stations.
Distributed processing networks are formed when two or more
computers communicate with each other to exchange information.
DiGITAL has developed two types of network products - OEenet for
communication between DIGITAL computers, and Internels for
communication between DIGITAL systems and other vendors' systems.

Using DEC net. computer system networks can be constructed to
facilitate remote communications and distributed computation. DEC net
is highly modular and flexible. It is a set of tools and services from
which a user selects whatever Is appropriate to build a network that will
satisfy the requirements of a particular application or application set.
DIGITAL Network Architecture (DNA) provides the common network
structure upon which all DECnet products are built. The architecture is
designed to handle a broad range of application requirements because
all the functions of the network - from the user Interface to physical
link control - are completely modular. DNA allows nodes to operate as
switches, front ends, terminal concentrators, or hosts.
DECSVSTEM-20 distributed proceSSing capabilities can be extended
with Internels or with PDP-11-based remote job entry stations.
TOPS-20 supports the 2780/3780 and the 2780/3780/HASP protocol
emulators. These two Internet products enable DECSVSTEM-20s to
communicate with IBM systems. Both perform emulation to
communicate with an IBM 360 or 370 host, and termination to
communicate with an IBM or IBM-type remote job entry station. These
emulators are well suited for batch-mode BISVNC communications.
TOPS-20 2780/3780/HASP Is a functionally enhanced 2780/3780.
Besides card reader. punch. and printer, It supports a terminal with
CRT and keyboard. With it. operators can communicate directly with
the IBM mainframe from a local termInal to control and check the
status 01 jobs on the IBM host. DIGITAL Internet products offer distinct
advantages over the IBM products whose protocols they emulate.
Users can also install and support a DX/TOPS-20 document
transmission package for word processing systems. DX/TOPS-20 links
the data processing and tile management capability of a DECSVSTEM20 with the editing and list processing capabilities of DIGITAL's WPS-8
word processing systems.

Ing and dumping the DN20 communications front end or
DN200-based RJE station (see NEreON below). With
NETCON , an operator can d isplay DECnet activity at the
local site. The user can d isplay statistics related to com·
munlcatlons lines, includ ing data on treHlc and errors.
Output can be directed to the term inal or to a report We.
Other utilities provide controlled local loopback test arrangements that enable users to perform a series of logl.
callests to aid in Isolating communication problems.

DECNEHO
DEenat expands the power 01 DIGITAL computer systems
so that each system can be used both independently, and
as part of a network . Each can also provide additional
computing bene Ills. There Is a DEena! product to support

each of DIGITAL's major operating systems.
DECnet-20 equips 8 OECSYSTEM·20 lor use in a computet network that can include other DECSYSTEM-20s,
VAXNMS systems, and PDP-II systems running the
RSX-l ' , lAS, ASTS/ E, CrS-500, or AT - 11 operating systems. Users access the network through the standard
TOPS-20 lIIe system Interface via MACRO·20 system calls.

When a TOPS-20 system operates as a node In a DECnet
conflguraUon, the functions II can perform depend somewhat on olher DECnet products in the configuraUon , ThIs
Is because two communicating nodes are always restricted to their common capabilities. Table 10-1 lists the various DECnet systems that can be configured with DECnet20 and the functions each can perform. Functions in the
left-hand column afe described In the section titled DECnet Functions below.

DECnet-20 olfers task-te-task communication, network

Iile translar, and network control capabilities.
Task-Ie-task communication permits user tasks running
on one system to communlcete Interactively with pro·
grams or tasks running on another. The local task uses the
TOPS·20 l ile system monitor calls to operate on flies on
network devices. Messages sent and received by user pro·
grams can be In any data format.

DECnet-20 also Includes onslle configuration tools and a
set of programs with wh ich the DECSYSTEM-2040 or 2060
user can build Site-specific, tailored software according 10
a DIGITAl·supplled "cookbook" procedure. This software
w i ll run I n the c ommunications Iront end of a
DECSVSTEM·20 or in a DN200-based RJE station .

DECSYSTEM·2040s and 20605 can support up to eight
physical links over serial synchronous communications
lines that can each support several logical links. DECSYS·
TEM·2020s can support two such links.
DECnet·20 network lIIe transler utilities permit a user to
trans fer sequential ASCII Illes between network systems.
Files can be transferred in either d irection between the
locally supported DECSYSTEM·20 devices and the file
system of an adjacent network system.

DIGITAL Network Architecture
DEenel Includes a set of layered network protocols, each
of which performs specific network functions. The protocols govern the formal, control, and sequencing of message exc hange In all DECnet products. Collectively, these
protocols are known as the DIGITAL Network Arch itecture
(DNA), end they provide a modular design lor DECnet. The

The DECnet·20 Network Control Program (NETCON utili·
ty) supports recording and displaying statistics and load·
Tabla 10·1
Product
ever. Ion)
Task·to-Task
Intersy11em Fl1e
Transfer
Network
Command
T«mlnal
Balch/Command
File Submission
- Requester
Batch/Command
FIle SubmistJon

-S_

Batch/Command
Ale Execution
Remota Ale

-..

DownUne System
loading
Downline
Taskloadlng

DEenat Product. and Function,

DECn.t·VAX
(1.3)

..,e.

DECn.t·20
(2.0)

...

DECne'·RT
(1 .1)

,
,

DECn.IIE
(1.1)

yes'

yo.

ye.

,..

ye.

yeo

,..

yes'

,eo

yes'

yes t

,..

DECne'·11 M DECn.t·llM DECn.t·llS
·PLUS (1.0)
(3.0)
(3.0)

.
.

,eo

,
,

.
..
,.

,
,..
,

,e'

ye.

DECn.t·IAS
(2.1)

..
,.
,eo
,..

• requester only

t server only
10-1

,
,

,e.

..
..

,e'

,e.

,
,
,

,eo

major protocols are DIGITAL Data Communications Mes·
sage Protocol (DOCMP), Network Services Protocol
(NSP), and Data Access Protocol (DAP).
DIGITAL Oat. Communication. M....g. Protocol DDCMP handles the physical link and physlcal·llnk error
recovery within DECne!. DDCMP operates either full· or
half·duplex with serial synchronous or asynchronous facll·
Itles In a point.to·polnt mode. DOCMP:
• Operates over a wide variety of hardware types
• Makes efficient use of full-duplex channel capacity
• Allows transmission of all data types (Including binary)
• Allows use of standard character·orlented communica·
tlons hardware

fashion, exchange data with programs or tasks on other
systems.
Table 10.1 also shows that many DECnet systems support
other leatures that are useful In a network envlronmenl
These Include:
• Intersystem file transler to move an entire data !lie
between systems at either program or operator requesl
Sequenttal ASCU liles are supported by all the systems
and are used In these transfers.

• Network command terminals to allow local users to log
onto like systems In the network as though their terml·
nals were directly connected to the remote system.
• Batch/command file submission to submit batch or
command files to remote systems for executIon .
• Batch/ command file execution to allow remote users to
submit for execution at the local node a batch or com·
mand lIIe that resides at a remote node.
• Remote lIIe access for tasks or programs to access se·
quenttal flies on remote nodes on a record·by·record
basis.
• Downllne system loading 10 allow Initial memory Images
for DECnet·11 systems In the network to be stored on
the local system and loaded on request Into other systems In the network . Remote systems usually require the
presence of a network bootstrap loader. Implemented In
read·only memory.
• Downline task loading to allow programs executable on
DECnet·11S systems In the network to be stored on the
local system and loaded on request Into other systems
under the Joint control of the operating systems at both
ends of the physical link. This feature and those listed
above simplify the operation of network systems that do
not have mass storage devices.

• Uses CRC·16 for error detection, with recovery by re·
transmIssion
• Is elfectlve on satellite links and other links with long
signal propagation delays
N.twork S.rvlc •• Protocol - NSP handles logical link
management functions within DECne!. NSP makes It pos·
sible for two programs on different machines to establish a
logical communications channel (log ical link) between the
programs and to exchange data using thIs loglcel link .
These progrems need not be aware either of the nature'of
the physical link (full. or half·duplex, parallel, or serial) or
the nature of the protocols supporting the physical link .
NSP has:
• Dynamic creation of logical links between tasks
• Exchange of data between tasks on a solicited basis
• Exchange of data between tasks on an unsolicited
(e.g.,lnterrupt) basis
• Ability to connect nodes dynamically within the network
once NSP Initialization occurs over a previously esta·
bllshed physical link
Data Acceas Protocol - CAP enables programs on one
node of the network to use the I/O services available on
other nodes. Some DECnet products provide facilities for
translating operatlng. system·speclflc I/O calls Into the
DAP standard and vice versa. Thus, DAP enables data
requests to be processed in a meaningful way by many
possibly heterogeneous operating systems. DAP's laclll·
ties include remote lUe access Including OPEN, READ,
WRITE, CLOSE, and DELETE for sequential and random
access flies and lor command flies.

Table 10·1 provides the Informat/on for determining If the
preceding functions are available on a particular DECnet
system. The descriptions above are the minimum capabill·
ties provided by a given function. Additional capabilities
may be available between two DECnet-connected sys·
tems.
DECnet·20 Capabilities
DECnet·20 provides the TOPS·20 user with network task·
to·task and flte transfer capabl1ltles. Local system or user
tasks can exchange Information with system or user tasks
runn ing In one or more adjacent nodes in a network.
TOPS·20 also provides file transfer between systems vIa
the Network File Transfer Program using the COPY, DE·
LETE, DIRECTORY, and SUBMIT commands.

Each DAP function requires support at both ends 01 the
link. At the local node where the user program Initiates a
data request, DAP must package the request for transmls·
slon through the network. At the remote node where the
device or fil e resides, CAP causes the appropriate actions.
Not all systems support both local and remote portions of
each CAP operation.

A local task communicates by usIng the TOPS·20 file system monitor calls 10 open flies, read and write Information.
and close flies on a pseudodevlce representing the network.

DECna! Function.
DIGITAL Network Architecture, Implemented across a
wide range 01 operatIng systems and hardware configura·
tlons, enables users to build a variety of networks. While
such networks have a common attribute, individual sya-tems withIn the network can have certain system·speclflc
attributes. As Indicated In Table 10·1 the common attrlb·
ute is task·to·task communication. Programs or tasks on
one system can create logical links and, In realtime

Below this user layer and transparent to the user, the net·
work protOCOl takes over. NSP software runnIng In the
main processor (and In the communications front end
when It Is part of the system) manages the actual transfer
of data over a logical link. User data Is first reformatted
Into network·compatlble segments and then transferred
over the logical link. NSP also generates the appropriate
control messages to open and close network connections.
10· 2

bootstrap programs to be used for downllne loading. On
the DECSYSTEM-2020, the LOAD LINE and DUMP LINE
commands load and dump the Internal line drivers. The
INITIATE LOGGING, TERMINATE LOGGING, and SET
LOGGiNG INTERVAL commands control the recording of
DECnet-20 line statistics.

NEreON - The NETCON utility (see above) is started at
system Initialization and runs under SYSJOB. NETCON
accepts operator commands which can:
• Oownllne-Ioad network software Into the communications front end of a OECSYSTEM-2040 or 2060
• Load network software Into the synchronous line controller of a DECSVSTEM-2020
• Upline-dump the memory of a communications front
end of a DECSVSTEM-2040 or 2060 Into a TOPS-20 file
• Log pertinent network load , dump, and line status Information Into the TOPS-20 SVSERR file

DECnet-20 User Intertace - With the network Ille transfer utility (NFT), users can conveniently copy flies to or
from a remote system, get 8 directory display for a specified account on a remote system, and submit a Job into the
remote system's batch queue.

• Display line statistics for any active node In the network
• Start, stop, and loop-back lines on a DECSVSTEM-2020

REMOTE JOB ENTRY STATIONS
TOPS-20 supports PDP-11-based remote Job entry stations. TOPS-20 support programs running on the DECSYSTEM-20 communicate with the remote PDP-11, using
a DECnet-20 task-to-task link. Each station supports up to
two high-speed synchronous lines, one lineprinter, and
one cardreader. Tasks running In the remote station drive
the lineprinter, cardreader and the console terminal.

DECnet-20 Operator Intertace - Operator commands to
NETCON fall into two classes: generic OECnet commands
and DECnet-20 commands.
Some DECnet commands are similar on all DECne! computer systems. These are the LOAD NODE and DUMP
NODE commands that downllne-Ioad and upline-dump
the communications front end, the SHOW QUEUE command that checks the status of any queued NETCON requests, and the SHOW COUNTS command that displays
Ilnecounter Information.

Remote stations can be downllne-Ioaded with the system
software and diagnOStics from the host computer. The stations provide the user with remote Job entry (remote batch)
capabilities to the DECSYSTEM-20. The remote stations
have power-fall and automatic restartcapabtlltles.

TOPS-20-speclflc commands are extensions to the generic DECnat commands necessary for implementation under
TOPS-20. On the DECSVSTEM-2040 or 2060, the SET
NODE command sets up operating characteristics of a
network node, and the SET SECONDARV- or TERTIARYLOAD-FILE command specllles the secondary or tertiary

ABLE

USER
B

DECSYSTEM-20

ABLER

USER
A

USER
C

INTERNET PROTOCOL EMULATORS
The Interconnection of DIGITAL systems and computers
built by other manufacturers Is supported by a family of
products called Internets. TOPS-20-supported Internels

if"

-- -------- --- ------

LOGICAL LINKS

,,
,

",",
'
"",
,
~, / \",
"" , ,
PHVSICAl
,~,
,
L1NKS~
CHARLY
27

BAKER

USER
D

1/
USER
E

1"(
[ USHER [

POP-ll

---------LOGICAL LINK

Figure 10-1
Logical and Physical Link.
10-3

[

USER
F

U~ER[

DECSVSTEM-2020

permit reliable bisynchronous links between DECSYSTEM-20s and IBM mainframe systems.
The TOPS-20 Internet products perform both emulation
and termination of IBM remote job entry stations. In emulation the software communicates with an IBM 360 or 370
host; In termination the software communicates with a remote station.
The DECSYSTEM-20 Internet products are TOPS-20
2780/ 3780 and 2780/ 3780/ HASP protocol emulators. The
2780/3780 protocol supports up to six synchronous communications lines on a communications front end connected to a DECSYSTEM-2040 or 2060. Up to two synchronous
lines are supported using the HASP protocol.
The TOPS-20 Internets:
• Allow submission from a DATA 100 rem ote station of
card decks containing TOPS-20 batch commands for
execution by the TOPS-20 host
• Allow a TOPS-20 uSer to submit card deck Images containing IBM JCL commands for processing by an IBM
360 or 370 remote host running one of the fOllowing
operating systems:
2780/3780

HASP

OSIVS2 (SVS) HASP II
OSIVS2 (MVS) JES2
OS/ MVT HASP JJ
OS/ MVT ASP
OSIVS2 (SVS) ASP

OS/ VS2(SVS) HASP
V4
OSIVS2 (MVS) JES2,
NJ
OSIVS2ASP
OSIVS2JES2

• Allow a TOPS-20 user to print a lIIe ata remote station
• Have features that support remote stations (2780/3780
termination)
HASP support allows the user at the remote station to
communicate with the operator Interface (OPR/ ORION) on
the TOPS·20 host directly from the operator terminal at
the remote slallon.
HASP also supports multiple 110 streams and several si·
multaneous devices. Wilh this multlleaving capability a
short Job can be Interleaved while a longer Job Is running .
TOPS-20 HASP supports full character compression.

Table 10·2

Remote Job Entry Termination
Support Protocol
2780

HASP

3780

MultIleaving
EBCDIC code

Extended retry

Muilirecord
transmission
(selectable,

x
x

Multlrecord
Interleaved
transmIssion

Transparency
(selectable)

x
x
x

CardreadSf

LlneprintSf

120..character line

x
x

Modem control
options

Unified system
Interlace

144·character line
(132 positions used)

Operator's console

Table 10·3

Remote Job Entry Emul.tlon
Emulated Protocol

Table 10·2 lists the features provided by TOPS·20 Inter·
nets In termination of remote job entry stations. Table 10-3
lists the features provided by TOPS·20 Internels when emulating remote job entry stations.
Internel software can transfer DECSYSTEM-20 GALAXY
batch Jobs from a remote slatlon to the OECSYSTEM-20
and execute them at the DECSYSTEM-20, or IBM JCL can
be sent 10 an IBM system for execution. In either case,
generaled log lt1es and oulput are returned to the sender.
DIGITAL software required to support this emulation and
termination Is the TOPS·20 operating system, the GAlAXY
system, and the Internet software. Allinternel communica·
tlons use the IBM Binary Synchronous protocol (BISYNC,
BSC) In half· duplex mode. BSC protocol permits only half·
duplex operation.

2780

3780

HASP
MutU·
leaving

EBCDIC code

Extended retry

Multlrecord
transmission
(selectable)

Multirecord
Interleaved
transmission

Transparency
(selectable)

Cardreadar

Lineprinter

144-charactSf line
(132 positions used)

ASCII graphics

Operator's console

10·4

X
X

Modem control
options

Unilied system
interface

DXITOPS-20 package Includes utility programs that con·
vert TOPS·20 flies stored In word processing format to
TOPS-20 Illes stored In ASClilormat. and vice versa.

In emulation, the Internet software makes the OECSYS·
TEM·20 appear to be 2780/3780 remote station when It
communicates with an IBM host. In termination, It does the
reverse - the OECSYSTEM·20 appears to be an IBM 360
or 370 while communlcallng with a remote batch station.

Communications between the WPS-8 system and the
TOPS·20 system use the OX error.correcting message
protocol.

Consider a OECSYSTEM·20 connected to a remote station
by dialup modems. The OECSYSTEM·20 Is running under
the TOPS· 20 operating system and has a ON20 communi·
cations Iront·end processor In addition to the usual con·
sole front·end processor. The communications Iront·end
contains the internet software. In a few steps, the remote
station user can send a GALAXY batch Job to execute on
the OECSYSTEM·20 and receive output returned to the
remote station printer.

OXITOPS·20 lets the WPS·8 system user:
• Store word processing format liles on a TOPS·20 sys·
tem and later retrieve them . By using the OECSYSTEM·
20 mass storage, the WPS·8 user can access a large
number of documents that might fill several document
flOPPY disks, including large documents titling an enUre
floppy.
• Use the high-speed OECSYSTEM·20 lineprinter con·
nected to the TOPS·20 system to print rough drafts and
other documents that do not require lelter·quallty print.
Ing . This Increases system throughput and the avallablll·
ty of the WPS·8 letter·quallty printer lor printing final
drafts. The TOPS·20 system user can output text flies
converted from the TOPS·20 liIe system on the WPS·8
letter.quallty printer.
• Create TOPS·20 source language and data flies offline
using the WPS-8 editor, and then transmit the lites to the
TOPS·20 system for processing.

OX/TOPS·20 OOCUMENT TRANSMISSION
OXITOPS·20 Is an optional, user·supported FORTRAN
software package that enables a WPS-8 word processing
system to communicate with the TOPS·20 system through
an asynchronous terminal Interface. The WPS· 8 system
appears to the host OECSYSTEM·20 to be a normal terml·
nal. OXITOPS-20 permits distributed stand·alone WPS·8
systems and the host TOPS·20 system to be linked togeth.
er lor better system utilization and data sharing. The

SYNCHRONOUS LINES
M

ON20

IBM 370

I---orl CONSOLE FE

'------'

1TTY,

Figure 10--2
2780/3780 Emulation

~ SYI"CI<R()N()USLINES

ON20

REMOTE
STATION

" L _ _ --'

~-~

] nY's

Flgur.10.3
2780/3780 Termination

10·5

...

11
Support
Services

DIGITAL offers comprehensive support services to help customers
before, during , and after system installation. DIGITAL's sales force Is
the primary contact for all products and services.
The support DIGITAL provides customers is apparent from the
beginning . Our sales representatives work closely with customers.
They study the application with the customer and determine specific
computing needs. Software and hardware specialists are available to
supplement the sales representative's product knowledge. These
specialists, trained to design systems using DIGITAL's standard and
special products, can be called in to answer specific questions.
Once the exact system requirements have been determined , the sales
representative helps the customer select a system configuration . Site
requirements such as adequate floor space, electrical capacity, air
conditioning , and humidity control are reviewed . Customers can
choose among various Field Service and Software Service
maintenance plans to suit individual needs and budgets.
If the application Is complex, the customer and DIGITAL's Software
Service organization can prepare a Customer Support Plan (CSP). The
CSP can consist of Software Product Services, Educational Services
courses, hardware maintenance requirements, and software
consulting services. It Identifies the customer's needs; the purposes ,
benefits, and details of the services recommended; how the services
will be delivered ; and how much they will cost.

Even before the OECSYSTEM·20 arrives, customers can train their
personnel through DIGITAL's comprehensive educational programs.
When a system is purchased, customers obtain training credIts that
they can apply to the cost of courses.
When a system is delivered, DIGITAL's hardware FIeld Service and
Software Support organizations are on hand to ensure smooth
Installation. DIGITAL's field specialists install hardware and software
and run tests to determine that the system has been installed correctly
and performs property.
Following installation, DIGITAL's support organizatIons are avaJlable to
help with special needs that may arise both during and after the
warranty period.

Product Services are avaHable to provide continued software support and maintenance. Designed to complement
DIGITAL hardware services. these Software Product Services offer the most comprehensive post-warranty support
In the industry:
• Software Product Updates. This service Is for customers
who Install their own software. It Includes Software Updates on the user's choice of available media and the
most recent documentation . Support services are not
provided but are available upon request.
• Self-Maintenance Service for Software. This contractual
service Includes SPR forms, a subscription to software
product and documentation updates. and a newsletter
that provides up-to-date Information on the software
product.

INSTALLATION
Upon delivery 01 the system DIGITAL's Field Service account representative schedules Installation of the hardware components. During installation Field Service engineers supervise the uncratlng and placement of equipment. cable connection, and power-up of components.
They lest the hardware by running 8 diagnostic package
and , once hardware reliability Is confirmed, they coordinate with software support personnel to Install and test the
o perati ng system.
Finally, DIGITAL Field Service and Software Services complete forms thai certify successful installation, and the cus-

tomer acknowledges system acceptance by signing the
Field Service labor Accounting and Reporting System

form.

Profeulonal Services
Whenever expert software assistance is needed,
DIGITAL's software consultants afe available. These soft·
ware specialists are experienced deSigners and writers of
custom software who can tailor DIGITAL software to specific needs. Their expertise can be applied to any phase of
an application - from analysis through Implementation.

SOFTWARE SERVICES
DIGITAL's Software Services organization specialists are
committed to maintaining high-level support for TOPS-20
software. They have the knowledge and experience necessary to analyze the user's needs and to Identify and deliver
the DIGITAL services that will help satisfy those needs. In
add ition to local Software SpecIalists. backup support
from regional and corporate levels is available when
necessary. DIGITAL's total software resources and expertise are available to support TOPS-20 and its various
dependent products.

Software specialist services are available on a resIdent or
per-call basis.
• Resident service Is for users who need lull-time, onslte
support. Aesldent consultants are particularly uselul in
new, complex installations or in critical, long-term proJects. Residents are available for a minimum of six
months; however, arrangements can be made to extend
the length of service to suit Individual needs.
• Per-ca11 service Is for customers with irregular or Infrequent consulting needs. Per-call (hourly) services are
ordered as needed and generally extend from a few
days to a few weeks.

Software Warranty
TOPS-20 Is a DIGITAL-supported software product engineered according to corporate quality standards. It operates in accordance with Its Software Product Description
(SPO). and carries DIGiTAl's commitment to provide support servIces lor the product. TOPS-20 must be Installed
by a qualif ied DIGITAL representative to qualify lor
software support.

You can learn more about DIGITAl's software services by
contacting your local OIGITA.L sales office.

DIGITAL-supported software products receive a 90-day
warranty following Installation. If. during the 90 days of
w arranty, a problem wlth the soltware Is encountered that
DIGITAL determines to be caused by a defect In the current, unaltered release of the product. the following remedial services are provided.
• If the software Is Inoperable, DIGITAL will apply a temporary correction or make a reasonable attempt to dev~op an emergency by-pass.

EDUCATIONAL SERVICES
DIGITAL provides comprehensive educational programs
to train users before, during, and after system Installation .
Instruction In system management. operations, hardware,
and software is given by trained specialists at DIGITAL's
worldwide training centers. Special onslte training and
custom courses can also be arranged .

• DIGITAL will help the customer prepare a Software
Performance Aeport (SPA). Using an SPA, users can
report problems with, or suggest enhancements to,
DIGITAL's software or documentation,

Course Option.
Courses fall Into three general categories:
• Generic Computer Courses. These provide a technical
foundation for personnel whose computer experience Is
limited.
• Software Systems Courses. These are designed to train
users, programmers, and operators to efficiently and
knowledgeably use DIGITAL's operating systems, languages, and utilities. Courses are available for both beginning and advanced users. The student is assumed to
have general computer and programming knowledge.
• Hardware Courses. These are designed for customers
who Intend to service their own equipment or who want a
general understanding 01 the components In their sys-

A fter the Initial purchase of a DIGITAL-supported product
license, additional copies can be purchased. These can
Inel ude support services or can be purchased as a " lIcense-to-Copy only," in which case neither media nor support services are Included.
TOPS-20 includes the standard services defined In the
TOPS-20 SPD. See your sales representative for these
details.
Software Product Services
After the 9O-day warranty period, two levels of Software

11-1

tern. Courses In generat hardware familiarization , hard·
ware troubleshooting, and hardware maintenance are
offered.
The courses can be iectureltab series regularly scheduled
to be taught at DIGITAL Training Centers, onslle courses
available by arrangement, or packaged courses.
• Onslte courses. Educational Services can conduct
group training courses at any convenient location such
as a customer's offIce or a company's training center.
Onslle Instruction eilmlnates travel expenses and allows
DIGITAL Instructors to emphasIze points of particular
value to Individual applications and operations.
• Packaged courses. Designed for students who wish to
learn computer fundamentals and TOPS·20 at a seltpaced rate, these packaged courses are portable, selfcontained, and modular In format. They are available either as audIo/visual courses or selt-paced Instruction
(SPI) workbook courses.
Audiovisual (A/V) courses use a combination of filmstrip/tape or videotape and workbooks. Among the AIV
courses offered are Introduction to Data Communications and Introduction to Digital Logic.
Sell-paced Instruction courses use a workbook with explanatory text, examples, and exercises. Among the SPi
courses available are DECSYSTEM-10/20 DBMS Concepts, DECSYSTEM-20 Operator TraIning , and
Programming In FORTRAN.
For users with special needs, Educational Services can
create a course tailored to unique applications, needs, and
schedules. These can be completely new or modifications
of existing courses. Custom courses can be conducted at
a DIGITAL Training Center or at a user's training center.
Contact your sales representative lor full details.

TOPS.20 Course.
DIGITAL Educational Services offers a comprehensive
software training program designed to address the need,
of all levels of TOPS·20 users. The courses consist of both
sell-paced and lectureltab courses that stress practical,
job-relevant skills required by TOPS-20 users, applications programmers, and system programm8f"s.
There are 12 TOPS·20 courses. Users' job requirements
dictate course content, and students can choose courses
from the approprIate sequence. Figure 11-1 Is a course
flowchart. The option to combine lectureltab and selfpaced instruction courses gives students the convenience
of learning at their own speeds and at their job sites, and
also the benefits of Instructor aid and the practical experience obtained In classroom and laboratory sessions.
The following are brIef descriptions of the DECSYSTEM20 courses shown In Figure 11-1.
TOPS·20 User provides a DECSYSTEM-20 software and
hardware overview and teaches students how to use the
program development features of the system. Disk file organization, system utilities, command language, and the
batch system are covered.
TOPS-20 AdmInIstratIon trains students In the skills need-

ed to administer a TOPS-20 system from startup and shutdown to system Installation. Disk file organization, man·
agement of resources, operation procedures, and system
security are also taught.
TOPS-20 Operator teaches operator duties and the basic
system procedures: startup, shutdown, recovery, backup,
and lile restoration.
TOPS-20 Assembly Language Programming covers the
DECSYSTEM-20 Instruction set and the MACRO Assam-

OI'(RATDA

.mE>
.........

SYIlUl
PROGIWOIEII

ASSEMBLY
UNGUABE

APftJCAnoN
PROGfWliIIIEA

COIOt
APPUCAnON
PROGIWlMEJI

Figure 11-1
TOP$·20 Courses
11-2

• A comprehensive site management guide

bier. Students learn to write programs that use monitor
calls and the MACRO library and to use Dynamic Debugging Technique.

Field Service's other onslte maintenance plan Is called Basic Service. DesIgned for customers who do not require a
fixed response time and continuous remedial eHorts, Basic Service provides:
• Next·day response
• Remedial service during coverage hours
• Priority-problem escalation
• Preventive maintenance during coverage hours
• Parts, labOr, and materials
• Instatiatlon of the latest engineering change orders
• An assIgned service representative
• A comprehensive site manegement guide

TOPS-20 COBOL teaches how to write COBOL applications programs under the TOPS·20 operating system. This
course assumes the user has prior knowledge of COBOl.
TOPS-20 System Programming covers system controls,
the accounting package, and advanced system calls.
TOPS-20 Applications Programming Techniques emphasizes the techniques that can be used to take advantage ot
system facilities with anention to the best overall design of
an application In the timesharing or production environment provided by TOPS-20. This course assumes the user
has prior knowledga of COBOL and FORTRAN.

Although standard coverage for both onslle service plans
Is eight hours a day, five days a week, customers cen opt
to extend their service coverage to 12, 16, or 24 hours,
Includ ing weekends and holidays.

TOPS·20 Operating System teaches the structure and the
basic components and functions of the monitor with emphasis on the batch system, command processor, and the
monhor's allocation and manipulation of system re-

sources.

Hardware maintenance on a per· call, IIme-and·materlals
basis Is also available.

DECSYSTEM-70120 DBMS Concepts Is an Introduction
that covers basic concepts and terminology, compares the
Inherent TOPS-20 data management system and DBMS
data management, and discusses their suitability to various applications.

More Information Is available on DIGITAL's Field Service
hardware maintenance offerings from your local DIGITAL
sales representative.

COMPUTER SPECIAL SYSTEMS
Computer Special Systems (CSS) provides design services and resultIng repeat products to DIGITAL's customers. Analysts, engineers, programmers, and manufactur'
Ing specialists can provide hardwere and softwere to customers whose needs are not met by DIGITAL's standerd
product offerings. In addition,
Is represented by
Marketing Representatives In the field.

TOPS-20 Monitor Intarnals covers the monitor In depth,
beyond the structural level, for the programmer responsl·
bIe for monitor patching and problem detection. Module
organization, monltor database, and Internal algorithms
are stressed.

ess

TOPS-20 Database Management System gives managers,
systems programmers, and applications programmers
both the conceptual understanding and programming
skills necessary to Implement DBMS systems.

ess provides custom systems and products In all of
DIGITAL's markets. Products and systems are analyzed,
designed , and Implemenled according to each customer's
goals and requirements. These products can range from
simple processor Interfaces to complete hardware and
software systems. All products carry DIGITAL's high standard of quellty, documentation. and field support. CSS design and project management services, evallable on a
contrect baslS, lnclude:
• Interfacing DIGITAL hardware with thet of other manu·
facturers, modifying standerd hardware, and designing
end building new equipment
• Designing and producing diagnostic systems and applications software, mod ifying and expanding standard
DIGITAL software systems. or building new software according to Individual needs
• Building complete hardware and software systems for
project managers oversee the
speclel eppllcatlons.
analysis, design , and Implementation of the system and
work with the customer to ensure proper Installation and
stert-up

OECnet-20 presents the network communications products of TOPS-20. Major emphasis Is placed on the software required to support network Interaction. In particular,
the data structures, message formats, and Interectlon
between software modules are described .

HARDWARE SERVICES
DIGITAL's Field Service organization oHers a range of
post-warranty hardware maintenance services. More than
10,000 Field Service personnel In over 400 locations
worldwide are ready to provide the support needed for
contlnUQ1Js productivity.
DECservlce Is DIGITAL's most comprehensive onsite
maintenance ptan. It Is designed lor customers who require uninterrupted system performance. DECservice Includes:

ess

• Four-hour response time
• Continuous-eHort remedial service
• Priority-problem escalatlon
• Scheduled preventive meintenance
• Parts, labor, and materials
• Installation of the latest engineering change orders
• An assigned service representative

Add itionally, customers cen receive DIGITAL's broad
range-of support services with any CSS system . Hardware
Is supported by DIGITAL's extensive Customer Service organization. Training Is available for allespects of
systems.

ess

11·3

The CSS solution puts DIGITAL's technology and experience at each customer's fingertips. II provides a cost-effectIve system desIgned for a specifIc appllcalfon and
backs the fInal product with high-quality service. Contact
your nearest DIGITAL sales office for further details.

CUSTOMER FINANCING
To simplify Ihe fInancIal consIderations Involved In acquIrIng a new computer, DIGITAL provIdes leasing and IInanclal counseling. The Customer FInance Department can
help customers acquire a DIGITAL system through a
lease, conditional sale, or similar financing agreement,
rather than an oUlright cash purchase.
For commercial businesses or private organizations DIGITAL has developed a program known as DIGITAL leasIng
with the U.S. leasing Corporallon of San Francisco.
DIGITAL leasing , a dIvision of U.S. leasIng, Is committed
solely to IInanclng DIGITAL computers. Representatives
are located In or near many of the DIGITAL District Sales
OffIces.
Federal, stale. and local government agencies have special contraclual needs and , In some cases, can benefit
from special tax privileges. For example, a slate or municipal agency qualilies for special Interest rates on Conditional Sales Agreements, rales that are slgnlflcanlly lower than
Ihose charged 10 commercIal customers. The Inlerest Income is free from federal and , In some cases, state income
taxes.
The fOllowing IInanclng Is available: Full Payout lease.
Conditional Sales Agreement, and Federal Government
lease to Ownership Agreement.
• Full Payout lease - This Is used primarily by commercial customers. II Is noncancellable, lasts three to five
years, and usually has a 10 percent purchase option at
Ihe end . No down payment Is required, and title remains
with the lessor. Flexible lease payment schedules can be
tailored to specific needs.
• Conditional Sales Agreement - This type of financing Is
used primarily by state and local governments. It Is noncancellable, and lasts one to five years. TIUe passes to
the customer, but DIGITAL retains a security Interest.
The customer owns the equipment free and clear at the
end of the term . Fiscal funding provisions are available
for state and local governments.
• Federal Government lease to Ownership Agreement _
This Is available only to approved federal government
agencies. It lasts one to five years, and is cancellable at
the end of each fiscal year for nonapproprlatlon of
funds. Ownersh ip passes to the customer at the end of
the term .
DIGITAL's Customer Financing group can provIde financIal counseling to help you decide which arrangement is
best for you. For more Information, conlact your local
DIGITAL sales office.

d irect factory ordering, the Direct Sales Catalog, and
worldwide support for theIr products.
ASCs are full-service centers established to fulfill the
needs of DIGITAL customers In major metropolitan areas.
The ASCs hOld a local Inventory of the most requested accessories, supplies, documentation, and add-on products,
for fast delivery. Full order processIng capability prOVIdes
access to A&SG's central Inventory In Nashua, New Hampshire. ASCs provIde first-class service and conV9nlenceto
DIGITAL's customers.
A&SG maintains a toillree telephone number lor custom.
ers to use when ordering accessories and supplies. The
majority of products are shiPPed within 48 hours of receipt
of order.
A&SG 's Direct Sales Catalog offers a broad range of com·
puter accessory and supply Items. These Include small
computer systems and their complementary options, ac·
cessorles, and operating supplies. The Direct Safes Csta·
log also features some DIGITAL hardware options such as
DECwriters, microcomputers, and associated options.
Hardware and software documentation Is also offered.
A&SG has a team of worldwide specialists and business
managers to support sales. This sales force is located in
the United States, Europe, and the General international
Area (GIA).

COMPUTER SUPPLIES
DIGITAL's Computer Supplies group maIntains B complete line of supplies specifically designed for use with
DIGITAL systems. These items facilitate reliable and effl.
clent system operation and Include:
• A family of magnetIc media such as disk cartridges, disk
packs, and floppy diskettes
• Sell-contained disk cartridge cleaners lor lasl and effl·
clent cleaning of front-loading or top·loading magnetic
disk cartridges
• Word processing supplies such as nylon and mylar ribbons. 11 types of print wheel, and filter screens for video
terminals
• Ribbons for DiGITAL's DECwrlter and DECprlnter terminals
The Computer Supplies group also offers computer
cabinetry for maIntaining supplies and protecting magnet·
ic medIa not In use. Cabinet interiors cen be customized
with various options to meellndlvldual needs. Options can
be conveniently rearranged or changed at any time to
adapt to future requirements. Also available are paper
baskets, work shelves, terminal lables, tape racks, papertape trays, and multipurpose binders.
Relying on DIGITAL for compuUng needs means a savings
In lime, money, and paperwork. Contact your sales representatlve for further information.

CUSTOMER SPARES
ACCESSORIES AND SUPPLIES GROUP

Customer Spares Is dedicated to supporting customers
who maintain their own computers. Customer Spares Is
organized Into three dlstlncl businesses: self-maintenance

DIGITAL's Accessories and Supplies Group (A&SG) maintaIns Accessories and Supplies Centers (ASes) and oilers
11-4

DECUS headquarters, located In Marlboro, Massachusetts, administers all international policies and activities.
DECUS is subdivided Into four chapters:

products (hardware and documentallon). system accessories, and low-volume lSI·l1 products. System accessories
Include products geared to the hardware builder. They allow easy expansion and (econflguratlon of DIGITAL sys-

tems and optrons.
Customer Spares sells modules, subassemblies, components, tools, and test equipment. Related services Involve
providIng aSSistance In selecting the proper parts and
expediting delivery during emergency situations.

DEC US
OECUS, the Digital Equipment Computer Users Society, is
one oltha largest and most active user groups In the computer Industry. It Is a not.for-prollt association supported
and admInistered by DIGITAL but actively controlled by Individuals who have purchased, leased, ordered, or used a
DIGITAL computer or who have a bone fide Interest In DECUS. Membership Is free and voluntary.

The goals of DECUS are to:
• Advance the art of computation through mutual educatIon and the exchange of Ideas and Information
• Establlsh standards and provide channels that ease the
exchange of computer programs

DECUS AUSTRALIAN
CHAPTER (Australia, Brunal,
New Zealand. Malaysia,
Singapore, Indonesia, PNG)
DECUS Australia
P.O, BoII:W
Chatswood
NSW2067
Australia

DECUS EUROPEAN
HEADQUARTERS (Europe,
Middle East, North Alrlca,
Eastern Europe)
DECUS Europe
P.O. BOil: 510
12, Av. Des Morglnes
CH·1213 Patil·laney lJGE
Swltz&fland

DECUS CANADIAN
CHAPTER
OECUS Canada
P.O. Boll: 13000
Kanata. Ontario
K2K, 2A6. Canada

DECUS UNITED STATES
CHAPTER (lor U.S. and an
others)
DECUS International
Headquarters
Digital Equipment
Corporallon
MR2·3/E55
One Iron Way
Marlboro, MA 01752 U.S.A

To further the goels of the society, DECUS serves Its members by holding symposia; maintaining a program library;
publishing an association newsletter, technical newsletters, and books; and supporting a number of special user
groups for special interests and locations.
• SymposIa - These are regularly scheduled meetings
held in each of the four chapters. They provide a forum
In whIch users of DIGITAL products can meet with other
users and with DIGITAL management, engineering, and
support personnel. Symposia give users an opportunity
to participate In DIGITAL product workshops and product planning feedback sessions. Many of the technical
papers and presentations from each symposium are
published as a book , the DECUS Proceedings. Copies of
the Proceedings are supplied to all symposia attendees
and can be purchased by any DECUS member,

• Provide feedback to DIGITAL on hardware and software

need.
• Advance the effective use of DIGITAL computers,
peripherals, and software by promoting the Interchange
of information

• Program Library - A major activity of DECUS Is the
Program Library. It contains over 1,700 active software
packages written and submitted by users. A wide range
01 software Is offered Including languages, editors, numerical functions, ulllitles, display routines, games, and
other types of application software. Library catalogs are
available for the PDP-8, PDP-l1/VAX, DECSVSTEM10/20. Catalogs are updated yearly and contain program descriptions and ordering Information. The programs are available at nominal service charges that cov·
er the cost of reproduction and media.
• Association Newsletter - Each DEC US chapter publishes and distributes to all chapter members a
newsletter of general DECUS news.
• Special Interest Groups - The focus of these groups Is
on operating systems, languages, processors, and applications. User groups are formed basically by geographical proll:lmlty, but can also share common specific
Interests. Many of these subgroups publish newsletters.
You can obtain a membership form for OECUS by contactIng the appropriate chapter office.
11-5

The
Glossary

glos·sa-ry (gI
basic tee

cal
ject or field, wit

glossa GLOSS2]
-gloa/sa-rist,

Absolute address A bInary number assIgned as the ad M
dress of a fixed memory storage location.
Absolute virtual address A fIxed locatIon in user vIrtual
address space whIch cannot be relocated by the software.
However, It cen stili be translated to a physical address by
the hardware.
AC

AND A logical operation such that the result Is true II all
conditions are true; otherwise the result is false.

Refer to Accumulator.

ANSI American National Standards Institute. An
organization that develops and publishes Industry stanM
dards.

Aceess privileges Attributes of a lIIe which specify the
class of users allowed to access the file and the type of
access they are allowed.

APl A Programming language. A problem-solving Ian·
guage with special features for handling arrays and for
performing mathematical functions.

Access time The time between requesting a data trans·
fer with a storage device and transferring the first bit.

Application program A program written lor or by users
that applies to their own work.

Account name An identifier that Indicates a user ac·
count for both fite structures and file access.

Archival
tape.

Account validation A program within the operating sys·
tem that is used to verify account names.

Storing a file of unChanging data on magnetic

Argument An Independent variable. For example: 1. A
variable or constant which is given In the call of a subroutine as information to II. 2. A variable upon whose value the
value of a function depends. 3. The known reference factor
necessary to lind an Item in a table or array (I.e., the index). Contrast with subcomm8nd.

Accumulator A hardware register and its associated
equipment In the arithmetic unit In which data can be
placed while the data Is beIng examined or manipulated.
ActIve process A process considered by the operating
system to be runnable.

Arithmetic unit The component of a computer where
arithmetic and logical operations are performed. Part of
the central processor.

Address 1. An Identification represented by a name, laM
bel, or number lor a regIster, a locatIon in storage, or any
other data source or desllnatlon In memory or on an adM
dressable storage device. 2. The part 01 an Instruction that
specifies the location of an operand of the Instruction.

ARPANET

Advanced Research Project Agency Network

Array An arrangement of elements In one or more dl·
menslons (I.e., an ordered arrangement of subscripted
variables).

Address constant A value or expression used In calcuM
lating absolute or virtual storage addresses.
Addressing Means by which localfons In storage are
specified or computed. Addresses may be specified as
absolute numbers or may be computed using absolute
values combIned with the contents of registers. The address computed may be used In an instruction or It may
indicate the location of the address to be actually used In
the Instruction.

ASCII American Standard Code for informatIon Interchange. A 7-bil code In which textual information is recorded. ASCII can represent 128 dlslfnct characters.
These characters are the uppercase and lowercase letters,
numbers, common punctuation marks, and special control
characters.
ASCII charecter set
ters.

Address mapping The assignment of user virtual address space to the physical address space In computer
memory. ThIs Is automatically performed by the monitor
and Is completely Invisible to user programs.

The set of 128 7Mblt ASCII charac-

Assemble To translate from a symbolic language program to a machine language program by substituting binary operation codes lor symbolic operation codes and
absolute or relocatable addresses for symbolic addresses.

ALGOL ALGOrithmic language. A scientifically oriented
language that contains a complete syntax for describing
computational algorithms.
AlGOTS

Analog Dealing in continuous variations or gradations,
as contrasted to discrete (In steps) variations. PertaIning to
data in the form of contInuously variable physIcal quantiM
ties.

Assembler A program which translates symbolic programs Into machine language programs and assigns
memory locations for variables and constants.

The ALGOL Object Time System.

Assembler directive The mnemonic used In the assembly language program to control or direct the assembly
process.

Alphanumeric Pertaining to the characters which Include all the letters of the alphabet and the numerals 0
through 9.

Assembly language A symbolic language that translates directly into machine language InstructIons. Usually
there Is one-Io-one relation between assembly language
Instructions and machine language Instructions.

Al TMODE A terminal key which is used to end some
command strings. See also ESCAPE.

G·,

Allembly liSting A printed list which Is an optional byproduct of an assembly run. It lists In sequence the symbolic code written by the programmer next to a representation of the actual machine Instructions generated. The
contents of the assembly listing are mostly under the
control of the programmer.
Alle mbly ti me The time at wh ich the assembler translates the symbolic machine language statements into mach ine Instructions.
Assigning a device Associating an 110 device with the
user's job either for the duration of the job or unlilihe user
relinquishes II.
Asynchronous 1. Pertaining to the procedure by which
the hardware can begin a second operation before waiting
for the first operation to be completed . 2. PertaIning to the
method of data transmission In which each character Is
sent with Its own synchronizing Information and no fjxed
time between consecutive characters.
Backg round program A program operating automatically at low prIority, when higher priority (foreground) programs are not using system resources.
Backspace To move backwards the logical poSitIon In a
file or on a line according to a prescribed format. For
example, magnetic tape units can be backspaced over a
file or a record . Some terminals allow backspacing to permit overprinting .
Backup fil e A copy of e file created for protection In case
the primary file Is Inadvertently destroyed.
Balance set The set of processes eligIble to run and
whose working sets fIIlnto memory simultaneously; periodically redefined by the schedu ler.
Base address An address used as a basis for computing the value of some other address. This computation Is
usually of the form: final address . base address (+ or -)
offset.
BASIC Beginner's All-purpose Symbolic Instruction
Code. An easily learned Interactive computer programming language.
Batch mode A system state in which programs are run
consecutively without terminal Interaction, as opposed to
timesharing.
Batch processing The technIque of executing a set of
computer programs without human InteractIon or direction during their execution.
Batch stream A collection of balch command strings
which are executed successively without the Intervention
of an operator.
BATCON The Batch Controller. This program reads a
Job's control file, starts the job, and controls the Job by
passing commands and data to II.
Baud

A unit of signaling speed equal to the number of

G-2

signal events per second. Baud Is the same as bits per
second when each signal event represents one bit.
Baud rate A fixed amount of time devoted to sending a
binary digit or bit.
Binary A characteristic, property, or condition In which
there are but two possible choices; for example, the binary
number system , using 2 as Its base, has the digIts 0 and 1.
Binary code A code that uses two distinct characters
only, usually 0 and 1.
Bit map A table describing the allocation of space or
resources. For example, each bit In the table Indicates the
slate of one segment 01 storage. as a block on a bulk
storage device.
BLISS-36 A programming language that enables users
to write programs consisting only of declarations that establish structure, and expressions that compute values. It Is
designed for Implementing system software.
Block (In a program) A segment of a program or a group
of Instructions In a program that performs some fun ction
that Is aloglcatly distinct subtask of the entire job.
Bootstrap A routfne or device desIgned to bring Itself
Into a desired state by means of Its own action, e.g., a
machine routine whose first Instructions are sufficient to
bring the rest of the routine Into the computer from an
Input device.
Bootstrap loader A routine whose Ilrst few instructions
are sufficient to bring the rest of the routine Inlo the computer from an Input device.
Branch A transfer of program control Instruction execution from one place In storage to another.
Breakpoint A locallon where program operation Is suspended to examine partial results. Breakpolnl s are used In
the debugging process.
Buffer A temporary storage area that may be a special
register or an area of storage. Buffers are oHen used to
hold data being passed between processes or between
devices which operate at different speeds or different
times.
Bu s

A circuit over which data Is transmitted.

Byte
unit.

A sequence 01 adjacent binary bits acted upon as a

Byte man ipulation The ability to manipulate, as Indlvldual lnstructlons, groups of bits as characters.
Cache memory Very fast semIconductor memory, usually small in size.
Call A branch, usually from one program to another.
Usually implied Is the ability, via appropriate Instructions,
to resume the first program from the locallon Just following
the point from which the origInal branch was made.

which Is set aside for common use by meny modules.
COMMON Is usually set up by modules written In the FORTRAN language. It Is used by Independently complied
modules to share the same data locations.

Card column One of the 80 vertical lines of 12 punching
positions on a punched card.
Card fleld A fixed number of consecutive card columns
assigned to a unit of Information.

Communication hardware Devices such as terminals,
modems, and acoustic couplers used for transmission,
switching, and termination of communication.

Cerd hopper The tray on a card processing machine
that holds the cards to be processed and makes them
avallable to the card feed mechanism .
COAIVE

Communication link The physical means of connecting
one device to another for transmitting and receiving data.

Thecardreader driver.

Central Processing Unit (CPU) 1. The part of the computer that moveS values, does arithmetic, and performs
comparisons and other manipulations, as well as keeping
track 01the current instruction, storage location, and operand addresses. 2. The unit of a computing system that
Includes the circuits controlling the InterpretatIon and execution 01 Instructions.

Communication procelSor A computer dedicated to
performing complete communication functions such as
message switching and data concentration.
Communication software Software written to explicitly
control communication between systems.
Compile 1. To produce a blnary-<:oded program from a
program written In source (symbolic) language, by SelectIng appropriate subroutines from a subroutine library, as
directed by the Instructions or other symbols of the source
program. The linkage Is supplied for combining the subroutines Into a workable program, and the subroutines
and linkage are translated Into binary code. 2. To prepare
a machine language program from a computer program
written In another programming language by making use
of the overall logic structure of the program , or generating
more than one machine Instruction for each symbolic
statement, or both, as well as performing the function of an
assembler.

Central site The location of the central computer. Used
in conjunction with remote communication to mean the
locallon 01the central processor as distinguished from the
location of the ram ate station.
Channel l . A path along which signals can be sent; for
example, data channel , output channel. 2. The portion of a
storage medium that Is accessible to a given reading station; lor example, track, band.
Character-orlented
character.

Operations performed on a single

Checkpoint A place In a routine where a check or a
recording 01 data for restart purposes Is performed .

Compil e r A program wh ich translates a high-level
source language Into a language suitable tor a particular
machine.

Closed subroutine A subroutine that can be stored at
one place and called from one or more calling routines.
Contrast with open subroutine.

Complement One's complement - to replace every 0
bit with a 1 bit and vice versa. Two's complement - to
form the one's complement and add 1.

COBOOT The COBOL Dynamic Debugging Technique
program.

Computer network
nected computers.

COBOL Common Business Oriented language. A programming language used in business data processing applications.

A complex of two or more Intercon-

Concealed submode A user submode that contains
proprietary Information .

COBOL complier A program that translates COBOL language statements Into machine language programs.

Concurrent processi ng The processing 01 two or more
actlvilles within the same Intervel of time.

COOASYl COnference on DAta SYstems language.
The conference that developed COBOL

Configuration A particular selection of computer, peripherals, and Interfacing equipment that function together.
A list of the devices and computers of a computer system.

Command The portion 01 an Instruction word that specifies the operation to be performed.

Connect tl ma A measure of system usage by a user,
usuelly the time Interval during which the user terminal
was online during a session. The wall-clock time between
login and logout. See also: CPU lime.

Command language The set of commands with which
the user informs the operating system of the desired func tion .
Command processor A componen t of the operating
system that reads and Interprets commands Issues by the
user.
Comm and atrlng A group of commands In a single line.

Console (CTY) The part of a computer used by the operator to determine the status of, and to control the opera·
tlon of the computer. The console has controls and Indicators used for manual operation of the computer.

C O M MON area

Context switchi ng

A section In a program's address space

G-a

The saving of sufficient hardware

and software Information of a process so that It may be
continued at a later time, and the res toring of similar Information relevant to another process. A common example of
context switching Is the temporary suspension of a user
program so that the monilor can execute a monitor call.
Control fil e The user-made file that directs the batch
system In the processing ol the user's job.
Control character A character whose purpose Is to control an acllon, such as a line spacing, pagIng, or termination of a job.
Controller A devIce or portion of a device that controls
the operation of connected units.
CPl

Conversational Programming language.

CPU time A measure of system usage, based on the
total amount of central processor time used. See also:

connect time.
CREF A program which produces a sequence-numbered assembly IIsling followed by tables showing crossreferences for all operand-type symbols, all user-defined
operators, or aU operation and pseudo-op codes.
Cross-reference listing A printed listing that Identifies
all references in an assembled program to each specific
label, macro, and/or operation code.
CTY

Refer to Console.

Cylinder The tracks of a disk storage device that can be
accessed without reposItioning the access mechanism.
Database A collection of related data Items processable
by one or more applications.
Database management A systematic approach to storIng, updating, and retrieving Information stored as data
items.
Data channel The device that passes data between the
memory system and a device controller.
Data Manipulation language (DMl) The language
used by the programmer to cause data to be transferred
between a program and the data base. An Incomplete language by Itself, It requires a host language.
DDT The Dynamic Debugging Technique program used
for online checkout, testing , examination, and modification
of object programs.
DDCMP Digital Data Communications Protocol. A uniform discipline for transmitting data belween nodes In a
polnt-Io-polnt or multipoint communication system. It governs parallel, serial-synchronous, or serial-asynchronous
transmission and receipt of data.

Default value The c hoi ce among excl u sive options
made by the system when no explicit choice Is specifled by
the user.
Delimiter A character that separates, terminates, and
organizes elements of a statement or program.
Demand paging 8rlnglng into memory only those pages
that are referenced, and bringing each page into memory
when It Is first referenced .
Device directory listing A list of all Illes on a specified
device. The list contains all flies with assocIated creallon
dates, total Iree blocks on the device, and number 01
blocks used by Illes.
Device handler or routine Roullnes that perform 1/ 0 for
specillc hardware devices. They usually translate logical
block numbers to physical addresses lor those devIces
that associate addresses with data. These routInes also
handle error recovery and provide device Independence In
operating systems.
Device Independence The ability to request 110 operatIons without regard to the characteristIcs 01 specIfic types
of 110 devices.
Diagnostic program A program that facilitates ma intenance by detection and Isolation 01malfunctions.
Direct address An address that specllles the location of
an operand. Contrast with Indlrecl address.
Directory device A storage retrieval device, such as a
disk, that contains information describing the names of
files and the layout of stored data. A directory of these files
is maintained on the device to locata the Illes. A directory
device must be randomly accessible.
Distributed network A network configuration in whIch
all node pairs are connected either dIrectly, or indirectly
through intermediate nodes.
Double preCision The use of two computer words to
represent a single number.
Dump 1. A listing of varia bles and their values, or allslIng of the values of locations in memory. 2. To copy the
contents of all or part of a storage medium, usually onto
another storage medium.
Effective address An address computed by taking all
the components Indicated In a given Instruction (such as
absolute value. contents of base register or instruction location register, Index registers, elc.) and combining them
to obtain a single address value.
ENO/ DEO facility A ll ows cooperating processes to
share resources and facilitates dynamic resource allocalion using the ENQ and DEO monitor calls.
ESCAPE A control key on a terminal that Is used for
com mand recognition and to end some command strings.

Debugg ing The process 01 locating any errors In a program, and correcting them.

Exclusive OR

A logical operatIon such that the result is

G·'
. . . . . . . . . . . . . . ._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _~
4
.

true II one and only one operand Is true, and false other.
wise.
EXEC Inlormal name for the TOPS·20 Command Proc.
essor. Contains routines which handle TOPS·20 com.
mands. These commands Interact with Ihe monitor.
An interrupt caused by a device

Frozen accen A type of access In which a flle can be
concurrently accessed by at most one user writing the l1Ie,
but by any number of users reading the file.

An error from which a program cannot re.-

Frozen proce.. A process whose execution Is suspended so Ihatltcan be continued where it was suspended.

External interrupt
conlroller.
Fatal error
cover.

Front-end processor The RSX·20F monitor. Controls
slow 110, main memory, and communication devices;
transfers data from such to rear-end memory.

FOB File Descriptor Block. Each tile has an associated
FOB that contains data concernIng the file. An FOB may be
up to 36 words.
Field A fixed number 01 consecutive characters asSigned to a unit of information.
FILDDT File Dynamic Debugging Technique. A version
of DDT used for examlng and changing a file on disk Instead of In memory. This program Is used to examine a
monitor lor debugging purposes.
File A collection 01 records. An organized collection of
information directed toward some purpose.
File-structured device A device on which data is given
names and arranged Into flies; the device also contains
d irectories of these names. Usually synonymous with
d irectory device.

Full-duplex operation Simultaneous, two-way communIcation between two pOints.
General register A register used lor operations such as
binary addition, subtraction, division, and multiplication.
General registers are usually used to modify an address.
Generation numbe, A number aSsociated with every file
that Indicates the number of revisions of that file that have
occurred. Every time the user edits the file, the generation
number Is typically Increased by 1.
Global A value dellned In one program module and used
In others. Globals are often called entry points In the module where they are defined and externals In the other modules that use them.
Global symbol A symbol accessible to modules other
Ihan where It is defined. The value of a global symbol la
placed In the loader's global symbol table when the
module conlalnlng the symbol definition Is loaded.

File descriptors Identifiers that describe an attribute of
a file. There are three types of lIIe descriptors; protection
numbers. account descriptors, and temporary tile descrlp.
tors.

Guide word A word output when you use recognition
that Indicates the type of argument that you can give lor
the next field.

File pOinter Indicates the last byte read from or written
to an open file.

Half-duplex Refers to an alternate, one way at a time,
Independent transmission between two points.

File protection code A code assigned to each file to
specify the access rights to the file.

Hardcopy A printed copy of machine output In a visually
readable form.

Flag A variable or register used to record the status of a
p rogram or device. In the latter case, also caJled a device
fla g .

Hardware Physical equipment, as opposed to a computer program or method of use.

Floating pOint A method for storing numeric data where
one part represents the position of the radix point (the
e xponent partj, and another part represents the significant
d ig it s (the fractional partj.

Host language A language Into which the Data Manipu_
lation language is Integrated to perform actions on the
database. The host language, for example, FORTRAN or
COBOL. Is used to manipulate the data once it Is in main
memory.

Aoellng-polnt binary A method for storing numeric data
w here the exponent occupies the first byte and the mantis.
sa resides In the next three or seven bytes. Used in FORT RAN IV representation.

Indexed addre.. An address lormed by add ing the
contents 01 an Index register to the contents of an address
field prior to or during the execution of a computer instruction.

FORDDT

Indexing A programming technique In wh ich different
locations are addressed by systemallcally changing the
contents of an Index register. The program uses the contents of the index register to compute the effective address.

FORTRAN's dynamic debugging tool .

FORTRAN Formula Translator. A procedure-oriented
programming language deSigned for solving scientifictYpe problems by expressing the procedure for their solution as arlthmellc formula.
FOROTS

Index reglate, A register whose contents are used In
computing addresses. The common lunctlon of such a

FORTRAN's obJect lime system

G·5

rr~------------------------------------------------------------------------------ -or

Job A set of one or more related processes normally
under control of a single user.

Indlre.ct address An address which indicates a storage
location where the address of the referenced operand or
another Indirect address Is to be found. Contrast with
direct addrsss.

Job number

Inferior procelll A process created by a superior process with the PUSH command. Inferior processes run under
the same Job 8S the superior process that created them.

JSB Job Storage Block . A table which contains all data
relevant to a given job.

Job status word A word containing bit flags Indicating
the status of the program currently in memory.

Kernel mode The executive submode in which I/O and
system-wide functions operate. Code executed in kernel
mode can access and alter aU of memory.

INFO The central information utility for IPCF. 11 performs
functions associated with names and PIDs.

LlBOL

Input buffer
computer.

A number assigned to ajob at login time.

The CQBQLobJect time system.

A temporary storage area for Input to the

Library A collection of standard routines available to
several programs.

Instruction A bit pattern Interpreted by the computer as
8 d irection to take 8 speclllc action.

Link To combine independently translated modules Into
one module In which all relocation of addresses has been
performed relative to that module and all external references to symbols have been resolved based on the definition of Internal symbols.

Instruction format The allocation to a specific function
of bits or characters of a machine Instruction.

Linker A program that combines many Input modules
into a single module prior to loading. Thus, it allows for
Independent compilations of modules. Typically, It satisfies global references and may combine control sections.

Instruction set A set 01 Instructions that a particular
computer can perform.
Interleaving To arrange parts 01 a sequence to alternate
with parts 01 another sequence. The sequence can be
things or events, and more than one sequence can be
Interleaved. In Interleaving, each sequence retains Its
Identity.

Linking loader A program that provides automatic loadIng, relocation, and linking of complier and assemblergenerated object modules.

Internal storage Addressable high-speed storage
directly controlled by the central processing unit.

Load module The output of the linker. A program In
formatted binary form ready for loading and executing on
a computer.

Interpreter A computer program or routine that translates and executes each source language statement before translating and executing the next one.

Local terminal A terminal connected directly to the
computer. Contrast with remote terminal.
Log file A file Into which BATCON writes all the Information passing between the job and its controlling terminal.
This file can be printed as the final step In BATCON's processing 01 a job.

Interrupt A break In the normal flow of control during the
execution of a program. When an Interrupt occurs, control
can be passed to a specific routine responsible for processing the Interrupt. The term Interrupt Is sometimes used
to refar to the condition causing the break Instead of the
break Itself.
Interrupt service routine
ternallnterrupt occurs.

Logical name An alphanumeric name chosen to represent a physical device and, optionally. a file name. This
name can be used in aU references to the device.

Routine entered when an ex-

LPTSPL The lineprinter spooler. Takes flies from d isk
and prints them on the lineprinter.

Interrupt vector add,e.. A unique address which
points to two consecutive memory locations containing the
start address of the Interrupt service routine and priority at
which the interrupt Is to be serviced.

Macro An Instruction In a source language that Is equivalent to a predefined sequence of machine Instructions,
or a command in a command language that Is equivalent
to a specified sequence of commands.

IPCF Inter Process Communication Fac ility. Allows
processes to communicate with each other via packets 01
Information or messages.

MACRO-20 A programming language that Is closer to
machine language than a high·level language such as
FORTRAN. Also called an assembly language or assembler.

JFN Job File Number. The unique Identifier of a particular file on a particular device during the execution 01 a
process. Used by the system as an index into the table of
files associated with the job. Also known as File Handle.

MAILER

G·6

A program that allows users to communicate

.... th each other by sending and receiving messages In the
form 01 data files.

Null character A control character that accomplishes
media 1111 or tlmallU.

M.'n program The module containing the address at
which object program execution normally begins. Usually,
the main program exercises primary control over the operations performed and calts subroutines to perform specilic
functions.

Object code Output from a complier or assembler which
Is Itself executable machine code.

Milk A bit pattern that seiects Irom a word in memory
those bits that are to be used In a subsequent operation. A
mask can be used to retain or eliminate portions of any
word in memory.
Ma .. storage An auxiliary storage 01 very large capacity
readily accessible to the CPU.
Memory pro tection A scheme lor preventing read
and/ or write access to certain areas 01 storage.
Mode

A method 01 operation.

Monitor 1. The collection 01 programs that schedules
and controls the operallon 01 user and system programs,
performs overlapped 110, provides context switching, and
allocales resources so that the computer's time Is elliclentty used . 2. The master control program that observes, supervises, controls, or verlfles the operations 01 a system.
MOS memory

Object module The primary output of an assembler or
compiler. It can be linked with other object modules and
loaded into a runnable program . Th is outpulls composed
of the relocalable machine language code for the Iranslated module (I.e.• link items), relocallon information, and the
corresponding symbol table listing the definition and use
01 symbols within the module.
Object time system The collection of modules that Is
cal1ed by the complied code lor a particular language in
order to perlorm various utility lunctlons. This collection
usually includes 1/ 0 and trap-handling routines. For example. FOROTS Is the object time system for the FORTRAN
language.
Offline llIe A lIIe that has been moved from dIsk to tape
by either the virtual disk system or the archive syslem.
Offline storage
CPU.

Storage not under the control of the

O"set The number 01 locations or bytes relative to the
base olan array, string , or block .

Metal-oxlde semiconductor memory.

Multiprocessing The simultaneous execution of two or
more computer programs (i.e.• processes) by two or more
interconnected processors sharing a common, Jointly addressable memory.
Multiprogramming The apparent simultaneous execution 01 two or more programs on a single computer by
timeSharing system components.

Operating system Software that controls the execution
01 computer programs and may provide scheduling , debugging , Input and output control , accounting , storage assignment. data management. and related services. Sometimes called the Supervisor, Executive, MonItor, Master
Control Program depending on the manulaclurer.
OR 1. (Inclusive) A logical operation such that the result
Is true If one or more operands are true, and false If all
operands are false. 2. (EXclUSive) A logical operallon such
that the result is true II one and only one operand Is true,
and faise II otherwise.

Multitasking The activation of several separate but
related tasks under a single program Idenllty.
Named tile A name-ordered collection of 36 bits whose
length is limited only by the available space on the device
and the user's maximum space allotment on that device.

Overlay 1. The lechnique 01 repeatedly using the same
sections of virtual address space to store different blocks
01 code and data during different stages 01 a program .
When one routine Is no longer needed in storage, another
roullne can replace all or part of It. 2. One 01 several blocks
01 code and data that potentially can occupy the same
section of virtual address space. 3. A segment 01 a program that Is brought Into main memory upon request.

Network control program (NCP) The module of an operating system In a host computer that establishes and
breaks toglcal connections and communicates with the
network on one side, and with user processes within the
host computer on the other side.
Node Any computer, communicallon controiler, terminal concentrator, or remote station in a computer network.

PA10S0 The TOPS-20 Compatibility Package that Is
merged with any program that uses TOPS-10 UUO's. It
simulates the operation 01 these UUOs by performIng the
appropriate JSYSs.

Nonresident soHware Programs that reside on the disk
until called lor by a user or other program.
Nonsharable program
has a separate copy.

Pack A removable set of disks mounted on a common
spindle.

A program for which each user

Packet A group of words transmitted by means of IPCF
to and from Jobs and system processes.

No op An Instruction that specifically Instructs the computer to do nothing, except to proceed to the next instruction in sequence.

Page

G-7

1. Any number of lines terminated with a form feed

character. 2. The smallest mappable unit of main memory
(512 words). 3. To remove selected parts of a user's pro.gram from memory.

Process Identifier An octal number In the ra nge 400001
to 400777 that Identifies an Inferior process to Its superior
process.

Page Fault When the system tries to refer to a page that
Is not In memory.

Program Counter (PC) A register that contains the address from which the next Instruction to be executed Is
fetched.

Paging The process of transmlltlng pages of Information
between main and secondary storage.
Parallel Processes
superior process.

Two processes created by the same

Parallel processing
more programs.

Concurrent execution of one or

Parity bit A binary digit appended to a group of bits to
make the sum of aU the bits always odd or always even.
Parity check A check that tests whether the number of
ones or zeros in an array of binary digits is correct. This
check helps ensure that the data read has not been unln·
tentronallyaltered .
PARSER A command language that allows commands
to be typed at the console and Invokes front·end tasks.
Parsing The systematic ordering of the elements In a
command or line of cod ing. For example, parSing a FOR·
TRAN command places the elements In standard form for
the complier.

Programmed operators Instructions that, Instead of
performing a hardware operation, cause a jump Into the
monitor system or the user area at a predetermined point
and perform a software operation. The monitor (or special
user code) Interprets these entries as commands from the
user program to perform specilled operations.
Program trap One of the non·hardwlred operation
codes that, when decoded by the processor, causes the
next Instruction to be executed from a specified address.
PROM

Programmable Aead·Only Memory.

Prompting A system feature that helps users by request·
Ing them to supply arguments necessary to continue processing.
Protection number A number given to every file that de·
lines wh ich users may access the file and what access Is to
be permitted to them.
PSB Process Storage Block. A table that contains all
monitor data for a given process.

Password The character string assigned to a user; It Is
usually known only to the user and the system. The pass·
word Is used to verify that a user Is entllled to run a Job
under a specific user name.

Pseudo-operation An Instruction to the assembler; an
operation code that Is not part of the computer'S herdware
command repertoire.

Peripheral equipment Any equipment distinct from the
CPU that provides the system with outside communlcatfon
or add itional faCilities.

PTY Pseudo· Teletype. A Simulated terminal, controlled
by the monitor, on which a subJob runs.
PTYCON

Program that controls PTYs.

Physlcaladdresa space A set of separate memory loca·
tlons where information can actually be stored (I.e., main
memory) for the purpose of program execution .

QUASAR A program that schedules requests for batch
lobs and output peripherals such as the line printer.

PIO Process ID. A number aSSigned to each process by
INFO and used by IPCF to route messages between
processes.

Queue A list of Items waiting to be scheduled or processed according to system , operator, or user.assfgned
priorities.

Pointer 1. A location or register containing an address
rather than data. A pOinter may be used In Indirect
addressing or in Indexing. 2. An Instruction Indicating the
address, position , and length of a byte of Information.

RAM Random·Access Memory. Any type of memory
with both read and write capability.

Polling A centrally controlled method of calling anum·
ber of points In some sequence to permit them to transmit
information.
Priority Interrupt An Interrupt that usurps control of the
computer from the program or monitor and Jumps to an
interrupt service routine If Its priority Is higher than the
interrupt currently being serviced.
Process An independent task capable of being run by
the mon itor and having a virtual address space of 512
pages. A process Is performed under a Job. Also known as
a fork or task.

Random Access Describes the process of retrieving or
depositing Information In storage where the time required
for such access Is Independent of the location of the Infor·
matlon most recently retrieved or deposited.
Recogn ition Input A method of typing TOPS·20 com·
mands in which the user types the unique portion of a
command or argument, and then presses the ESC key.
The system attempts to recognize what the user wants to
type and either prints lis assumption or rings the terminal
bell prompting the user to type more. The user can then
type more and try for recognllion again.
Reentrant program

A program conslstfng of sharable

G·8
=

..-----------------------------

code that can have several simultaneous Independent

users.
R.g'lter

A device capable of storing a specified amount

01 data, usually one word.

Relative addt... The specification of a memory loea·
lion as an otfsellrom 8 base address. The computer sums
the base address and olfset to ascertain the relative ad·
dress. ThIs type 01 addressing allows the relocation of Instructions because the system moves all of the data being
addressed by the same amount - the offset.
REl file

RUBOUT A key (also labeled DEL) on the term inal
keyboard that erases characters that the user has typed.
RUNOFF A program that facilitates the preparation of
typed or printed manuscripts by performing formatting ,
case sh ifting, line Justification , page numbering, tltUng ,
and Indexing .
Run-time

Scheduling algorithm An algorithm that determines the
order In which competing Jobs are allowed to use resources.

A lite containing one or more relocatable object

modules.

Schema

Rllocatable address An address within 8 module that Is
specified as an offsetlrom the first location In that module.

Sharable program A program wh ich can be used by
several users at a time.
Shared Pages When the same page 15 represented In
more than one process address space. Allows two or more
processes to Identify and use the same page of physical
storage.

Remote batch A feature that allows data 110 and job
control of batch processing from a distant terminal over a
communication link.

Software Interrupt System Interprets the sequential
fl ow of program execution under a variety of conditions.

Remote Job entry The Input of batch jobs via a
cardreader at a remote site and the receipt of job output
via a printer or cardpunch at a remote site.

Source code Text. usually In the form 01 an ASCII-Iormatted file wh ich represents a program. Such 8 file can be
processed by an appropriate system complier or assembler to produce an object module.

Remote station Unit record and/ or terminal equipment,
located at a distance from a data processing system with
which il communicates via communication lines.

Spooling The technique by which output to slow-speed
devices Is placed Into queues on faster devices (such as
disk) to await transmission to the slower devices; this allows more efficient use 01 Ihe particular device, main
memory, and the central processor unit.

In memory, as opposed to being stored ex-

Resource An available portion of the computer's machinery or software.

SPRINT The batch Input processor. SPRINT reads any
sequential Input stream , sets up the job's controlllle and
data files, and enters the Job Into the batch Input queue.

Remote Job Entry.

ROM Read-Only Memory. A special memory that can be
read from, but not written Inlo.

SPROUT
Root directory
ries.

High-capacity magnetic storage,

Sequential access Obtaining data Irom an 110 device In
a serial manner only.

Reloeatable symbol. Symbolic names whose associated value Is an offset Irom the base (beginning) of a control
section. Such a symbol's value depends on the address 01
the control section and must be relocated each time the
control section Is asslgned an address by the Linker.

RJE

A complete description of a data base.

Secondary storage
such as disks.

Relocatable code Code written so that It can be located
and executed In any part 01 memory, once it has been
linked by the linker.

Resident
ternally.

The time In which a program Is executed.

The card punch spooler.

Contains the names of all users' directoSubcommand A qualifier given wlth a command that
causes the command to operate In a specific way. Contrast
with Argument.

Root segment The segment of an overlay tree that, once
loaded , remains in memory during the execution of the
task.

Subjob A job created by another Job running on the
same physical terminal as the job that created It.

Route through The ability of a node In a network to receive data destined for another node and to forward that
data directly to its destination or to another Intermediate
node.

Subroutine A routine designed to be used by other routines to accomplish a specifiC task.
Subscript A numeric valued expression or expression
element which 15 appended to a local or global variable
name to uniquely Identify specific elements 01 an array.

Routine A set of Instructions and data for performing
one or more specific functions.

G·g

--------------------------------------------------------------------------------- ~

S wa pp i ng The movement of programs and data
between main memory and high-speed secondary storage.

instruction. The address location from which the Jump Is
made is recorded. II Is distinguished from an Interrupt,
which Is caused by an external event.

Symbolic address An address used to specify a storage
locetion In the context of a particular program. Symbolic
addresses must then be translated Into relocatable (or absolute) addresses by the assembler.

Tree structure A hierarchical structure In which each
element may be related to any number of elements at any
level below It, but to only one element above It In the hierarchy.

Symbolic name Refers to a label used In programs written In source languages to reler to data elements, peripheral devices, Instructions, etc.

Un it-record device 110 equIpment such as a card reader, cardpunch , or lineprinter.

Symbol table A table containing entries and binary
values for each symbol defined or used within a module.
This table generally contains eddltionallnformatlon about
the way In which the symbol was defined In the module.
SYSJOB A program that controls several active system
processes simultaneously.
Tape la bel A record used to Identify the magnetic tape
on which It resides.
Termina l u ssr
system.

Anyone who Is eligible to log onto the

Thawed Access A type of access that allows a lIIe to be
accessed even if other users are reading and writing the
lIIe.
Thrashi ng When the system spends an excessive amount of time swapping pages between memory and the
disk.
Throughput The measure of the amount of informatIon a
computer can input, process, and output In a given time.
TimesharIng 1. A means of sharing the facilities of a
computer between several users by giving each one a
fraction of a second at a time to execute his program. 2.
Pertaining to the interleaved use of the lime of a device. 3.
A method of allocating central processor time and other
computer resources to multiple users so that the computer
appears to process a number at programs simultaneously;
multiprogramming.
Ti me slice The period of time allocated by the operating
system to process a particular partition's program. This
term is synonymous with "timesharing Interval."
Trap 1. An automatic transfer of control to a prespeclfled
routine that can be caused by software or hardware. 2. A
conditional Jump to a known locallon performed automatically by hardware as a side effect of executing a processor

G-10

User name The unIque Identifier assigned to each user
of the system. Also serves as the name of the user's primary directory.
User programs A group of programs, subprograms , or
subroutines written by a user.
VarIable
values.

Any enllty that can assume any of a given set of

Virt ual addre ss A number which Indicates relative
position within a collection of logically related granules of a
storage medium . The fact that the medium Itself may be
virtual Is of little consequence; the ability to deal with a
hierarchical or multilevel memory as If It were one medium
Is one of the principal advantages of systems supporting
virtual addressing.
Virtual address space The upper extent of the size of
any program the user may create and run.
Virtual memory The space on secondary storage where
the monitor keeps a reference copy of the job's Image tor
when the Job has to be swapped out of memory to make
room for other Jobs.
Virtual memory pointer Pointer used to keep track of
the program segments In memory.
Wa lt state The condition of a process that Is dependent
on one or more events In order to enter the active state.
Same as a blocked state.
Word An ordered set of bits that occupies one storage
locatIon and is treated by the computer as a unit.
Working set The set of pages most recently accessed by
a process. The working set is modlfled as the process
runs.
Write-lock condition The condition of a device that Is
protected against any transfers which would write Information to It.

•

Accessories and Supplies Group (MSO),

,,-4

byte manipulation, 5-3, 6-2
byle Iranslers, 5·10

accounting lacUity, 3-3

addressing, vlnual memory. 4....

cache memories, 2·1
In KLlO·E procesaor, 5·5-5·7
In KS10 processor, 8-2
CALL statement, 8·7
cardreaders,7-4
CASE slalement, 8-5
CD20cardreaders, 7-4
centralized quaue manager, 4·1-4·2
central processing units - see pr0C8uon
CHAIN Itatement, 8·7
CHANGE atatement, 8· 6
chennel bus (Cbus), 5-9
Charebend, 7-3
characlerslor APL, 8·8
class IChedullng, 3·2-3·3
COBOOT (COBOL debugger), 8·3
COBOL, 3·1 , 8-2-8-4
COBOL-58, 8-2, 8-4
COBOL·74, 6-2, 8-4
COOASYl,9·1
COGO·20 utility, g. 4
command language, 2·1-2-2
Command Language Processor, 2-3, 4-1
Invoked by jobs, 4·2
command parser, 5·8
Command Recognition, 2·2
commercial eppllcatlons, 2·1
communications, 2·1
console lurn:tlonslor, 4-7
interlaces lor, 7·6
KL IO-E I/ O sub.yltem and, 5-8
by processes, 4· 2-"-3
software lor, 2-2-2-3, 10-1-10·5
Computer Special Systems (CSS), 11-3-11-4
Computer Supplies group, 11·4
conditional sales agreements, II·"
condlllOnal slatements, 8-7
console Ironl·end processors, 4-6-4-7
KlIO·E,5·7-5·8
console mode, 6-4-6-5
console subsystems, 2·1, 4·7
KL 100E Iront-end subsyslem, 5-7-5-6
lor KS I 0 processor, 6-4-6-5
console terminals (CTYa), 6-4-6-5
Control RAM Addres. (CRA) Module, 8-1
Control RAM Memory (CRM) Module, 6-1
Conventional Format, 8-4
conversion packages for APL, 8·9
copy·on-wrlte lealure, 2-2. 4-5
Core Status Table, 6-4
Cour.... ll-l-11·3
CPL (Conversallonal Programming
Language), 3-1. 8-10
CPUs - see processors
CREF program, 3-3
CTYs (console terminals), 6-4-6-5
cuslomer financing, 11· 4
Customer Spares, 11-4-1\·5
cyclic redundancy checking (CRC), 7-1

address space

in KllO-E processor. 5·7
in KS 10 processor. &-3
AlGOL. 3-1, 8-4-8-5
ALGOL·20,6-4-8-5
ALGOTS (ALGOL ob}ecl-tlme system), 8-5

APL.3-1,8-7-8·9
APt-SF, 8-7-8-9
apptlcetion programmers, 3-1
applications. 2-1, 9-1-9-4
application tooll, 3-1

arch,tecture
DNA. 10-1-10-2

KlIO-E memory subsyllemin, 5-5
01 KL IOE processor, 5-1
01 K510 proceuor. 6-1-6-3
archiving files, 4·6
archiving/migration lealure, 3-3

."thmellC
using BAStc;..PLUS-2, 8·7
flxed_ and floating-point. 5·3, 6-2

atithmebC tMUng ~llruCIIons,~. 6-2
ARPANET (Advanced Research Project
Agency Network, 2-3

auemblef language. 3-1,8-'
assignment statemenls. 8-8
authorization 01 users, 3-2
automatic restlrt., 2-3, 3-3
Automatic Volume Recognition (AVR), 4-8
aUl(Jllary processors, 7-6

availablhty. 2-3

8
backup. 3-3
balance sets, 4-2--4.4
8ASIC-PLt:JS-2, 3-1,8+5-8.7
Basic Service, 11·3
balch proce"lng, 2·2, 4·1-..·2
by appllcaUon programmers, 3-1
in networks, 10-2
batch streams, 3-3
bias con trolleature, 3-3
Bmary Synchronous protocol
(BISYNC: esC), 4-10
BLISS-36, 3-1-3-2, 8-9-8-10
BLOCK-IN/BLOCK-OUT instruction, 5-4
block slructure In ALGOL, 8·4
block transfer InltrucUons, 5-4
bootstrapping reliability and, 2-3
brat'ICh statements, 8-8
buffers
In APL, 8-9
in paper tape reader/punch, 7-4
print line, 7-2, 7-3

.u...
In KL 100E processor, 5-1,5-8-5-10
KS10, 6-1-6-2
Buainess instruction Set. 5-4, 6-3

Index

data
In "PL, 8·8
In BASIC·PlUS·2, 8-6-8-7
management 01, 9-1-9-4
sharing 01, 4·6
types 0111'1 COBOL, 8-3
Data Access Protocol (OAP), 10-2
Oataba.. Control System (OBCS), 9-2
database management. 3·1. 9-1-9-2
DaIS Dellnl\lon Language (DOl), 9·1
dala dictionary, 9·3
Oala Manipulation language (OML). 9-1-9-2
Data Path Executive (OPE Module), 6-1
Data Palh Memory (OPM) Module, 6-1
OAVFUa (dlrect·access vertlcallorm units),

'·3
DBMS (datsbase management system). 3-1 ,
9- 1-9-3
OBMS·20, 9·1-9·2
OOCMP (DIGITAL Data Communications
Message Protocol), 10·2
DOT (DIGITAL Debugging Tool). 3-4, 8·1
debugging
In APl, 8· 9
In BASIC-PlUS-2. 8-7
in BUSS·36, 8-9
in COBOL, 8-3
InCPl. 9-10
DOT lor. 8·'
In FORTRAN, 8-2
DECnet· 20, 2·2. 10·1-10·3
OECservlce,11 ·3
DECSYSTEM·20 ALGOL. 3·1
OECSYSTEM·20 COBOL, 3·1
DECSYSTEM·20 FORTRAN, 3-1
OECSYSTEM-2020
KS10 processor and, 6-1-6·5 lsee slso
KS 10 proce$$or; KS sys tems)
DECUS (Digital Equipment Computar Users
Society). 11-5
deferred mode, 9·2-9·3
davlces - see hardware; peripheral,
OH11 programmable asynchronoua serla' line
multiplexers, 7-6
diagnostics
console and, 4-7
In KL 10-E processors, 5-1. 5·7
KUNIK lor, 2-1
In KS 10 processor, 6·4
online, 2·3
Oigi\al Oats Communications Message
Protocol{DOCMP). 10-2
Digital Equipment Computer Users Society
(OECUS),11-5
DIGITAL Network Archllecture(ONA),
10-1-10-2
Digital ten·to-eleven (OTE·20) Interface. 5-7,

dlrect·acceas vertlcalform units (OAVFUsj,

'·3
directorlea
In caches, 5-6
user file. 4-6
direct proceS6 conlrol, 4-2
disk controllers. 7-1

diSk 1/0 statistics. 3-3
disks. 7-1
RP06 drives. 5-8
storage quotas on. 3-2
OL 11 serial line asynchronous Interfaces. 7-6
ON20 communications Iront end. 7-8, 10-5
DNA (DIGITAL Network Architecture),
10-1-10-2
double-precision Iloating-polnt format. 5-3
OTE Interlace. 5-2. 5-7.5-10.7-8
~UMPER program, 3"
OUPII single synchronous Une Interfaces. 7-6
OXITOPS-20 document transmission. 10-5
OZ11 terminal line Interfaces. 7-8
E

EBox (execution Box), 5-1-5-4
EBR register. 4-5
EDIT program, 3-4
Educational Servlcas. 11_1_11_3
enqueue/dequeue (ENQ/OEQ) lacility. 4-3
ENTER lacility. 8-3
errors
analysls 01 and recovery from In APl, 8-9
In batch processing, 4_1
corrections for In tape systems, 7-2
detection and reporting of. 2-3
handlll'lg of In BASiC-PLUS-2, 8-7
Interrupt p!"ocesslng lor. 2-1
lournals for recovety from, 9-2
In MOS memory, 5-5, 6-4
Execution Box (EBOX). 5-1-5-4
execuUon mode. 8-S
executive mode. 5-2. 6-3
F

last reg ister blocks, 5-4
Field Service. 11-1, 11-3
FllCOM program. 3-3
tile director ies, 4·6
liIe-handling services, 3-1
liles, 4-5
In APL. 6-9
In 8ASIC-PlUS-2, 6-6
In COBOL. 6-3
for data bases. 9-1
In DBMS. 9-3
In networks, 10-2
tile system. 2-2. 4-5-4-6
financing. t 1-4
fixedlloatlng conversion Instructions. 5-3. 6-2
fixed-point arlthmetk:, 5-3. 6-2
flags for MOS memory errors. 5-5
ftotIUng point arithmetic, 5-3
FOROOT debugger, 8-2
lorma. TRAFFIC-2O for. 3-1, 9-4
FOROTS (FORTRAN obJect· time system), 8-1.

8-2
FORTRAN, 3-1. 8-1-8-2
FORTRAN IV, 6-2
FORTRAN-208-1-S-2,lront-end
subsystems. 2-1, 4-7
ON20communications Iront end, 7-6, 10-5
In KL 10-E processor, 5-7-5-8
full-word data transmission, 5-3. 6-2
function-defin ition mode. 8-8
G

GALAXY system. 10-4. 10-5
GCR mode, 7-2

general purpose registers. 5-4. 6-2
geometry COGO-20 for, 9-4
groups. 4-6
H
hall-word data transmission. 5-3, 6-2
hardcopy term inals, 7-4-7-5
hardware
Installation 01. 11-1
KltO-E processors, 5-1-5-10
KS10 processors, 6-1-6-2
mess storage peripherals. 7-1-7-2
reliability of. 2-3
support services for, 11-3
terminals and Interfaces. 7"-7-6
unit record peripherals. 7-2-7"
Hardware Page Table. 4-5
HASP protocol emulators. 10-4
help facilities. 2-2

IBM Emulation/ Termination. 2-2
IBM systems.lnternets lor , 10·4
Immediate mode. 6-7, 8-8, 6-10
Immediate Mode Pointer. 4-5
Inde)!;ed access method. 4-4
Ind8)(ed sequential-access mode (ISAM), 8-3
IndireCt pointers. 6-4
inferior processes. 4-2
input queues, 4-2
Input spoolers. 4-1
Installation, 11-1
instructions and Instruction sell
for KlIo-E processor. 5_1_5"
lor KSIOprocessor. 6-2-6-3
Interactlva mode. 9-2
interactive p!"ocessJng
by applicalon programmers, 3-1
In COBOL, 8-3
Interactive Query Language (IOl). 9-2-9-4
interfaces. 7-6
OTE, 5-2. 5-7. 5-10
for NETCON. 10-3
USART,6"
Internal memory in Kll0-E processor. 5-5
Internets, 10-3-10-5
Interpr0C9ss Communications Facility (IPCF).

4-2
Inlerupts, 2-1
priority systam for, 5-4
software Interrupt system for. 4-2
interval timer, 5-4
I/O instructJons. 5-3, 5-4
110 subsystems In KllO-E pr ocessor, 5-1.
5-8-5-10
IPCF (in terprocess Communication Facility).

4-2
IOL (Interactive Ouery lal'lguage), 9-2-9"
ISAM (Indexed sequential access mode), 8-3

J
jobs. 4-2
balch processing of. 4-1
Job statistics. 3-3
}aurnals.9-2
JSYS Instruction. 5-4
K
Kll0 processor, 2-1
KllO-E processor. 5-1-5-10
fixed-point arithmetic on, 6-2

KLiNIK (diagnostics). 2-1, 5-7-5-8
KLINIT (Initialization program), 5-6
Kl systems
OHlt prorammable asynchronou s serial
line multiplexers for, 7-8
line Interfaces supported on. 7-4
KMC ll-A auxiliary processors, 7-6
KSIO bus. 6-1-6-2
KSIO processor, 2-1, 6-1-6-5
peripherals supported on, 7-1
KS systems
Interfaces for. 7-6
line Interlaces supported on. 7-4
L
LA38 OECwrlter IV hardcopy terminal s, 7-5
LA 120 hardcopy terminals. 7-4-7-5
labeling of tapes. 4-8
Isnguages. 2-1. 2-2, 3-t
APL.8-7-8-9
BASIC_PLUS_2.8_5-8_7
COBOL. 8-2-8-5
CPl.6-10
FORTRAN. 6-1-8-2
leasll'lg.ll-4
library facilities In COBOL. 8-3
lineprlnters, 7-2-7"
output spooling for. 4-2
LINK program. 3-4
log mes, 4-1
logical communications links. 10-2
logical testing Instructions. 5-3, 6-2-6-3
logic Instructions, 5-3. 6-2
longitudinal redundancy chec:kll'lg (lRC). 7-1
lP0511neprlnters.7-2-7-3
lP07I1neprinters.7-3
lP14 IIneprinters, 7-3
lP20 lineprinter controllers. 7-2. 7-3
lP20-A and -B lineprlnters, 7-2-7-3
lP2O-C and - 0 IIneprlnters. 7-3
lP200 tine p!"lnters. 7_3-7_4
M
MACOR (assembly language). 3-1, 8-1
MAIL program. 3-3
maintenance
console and. 4-7
01 hardware, 11 -3
for LA3S hardcopy terminals, 7-5
of software. 2-3. 11-1
MAKLIB program. 3-3
mapping
In KlIo-e processor. 5-7
In KS 10 processor. 6-3---8-4
MASSBUS In KL Io-Eprocessor, 5-1. 5-9
mass storage - see memory
mstri)!; manipulation. 8-7
MBox (memory control unit). 5-1. 5-5. 5-8

memory, 2-1
disk storage quotas for. 3-2
msss perIpherals for, 7-1-7-2
organization 01. 2-2
sharing of, 4-3
virtual. 4"-4-5. 6-6
memory control unit (MBo)!.), 5-1. 5-5, 5-6
memory mapping. 5-7.6-3--8-4
memory status table. 4-5
memory subsystems
In KLIO-E processor, 5-5-5-7
In KSIO processor. 6-3--8-4

........-------------------messages MAIL program lor, 3-3
meters. S-4
microprogramming, &-1
mlcrostore,6-2
mod..
lor APL language statements, 8-8

OTE-20 operating. 5-10
pn;)(:esllOf, 5-2, 8-3
modification Instructions, 5-3, &-2--6-3
monitor, 4-3-4-4
monitor caJitr., 3-2
Monitor Page Table. 4-5
monitor statistics, 3-3

MOS (Metal Oxide SemIConductor) memory,
5-5,8--4

MS 10 memory. 604
multiplexed 110 bus, 5-8
multiprogramming environments, .yetam
programming for,

3-'

NETeON (Network Control Program) utility,
1(1.1,10-3

network lile Iransler (Nfl) utility. 10-2. 10-3
networks

OECnet-20,IG-l-10-3
ON20 comrnunlcatlon.'ronl end lor, 7-8

Internats, lG-3-1 0-5
Network ServIces Protocol (NSP). 10-2
NRZI mode, 7-2
numbers flxed- and nolting-point, 5-3, 8-2

o
object-time IystfIfTII

AlGOTS, 8-5

FOROTS,a.,.1,8-2
offset mode, 5-4

ON ERROA GOlD .tatamenl, 8-7
OJ)efatlng system - see TOPS·20
operators - see sys/arn operstors
aPR unified system Interlace. 3-3
optimization In FORTRAN·20, 8·2

output spoolers. "·2
OWN variables (ALGOL). 8-5

P
pages.......- .. ·5
In caches, 5·6
In KllQ...E memory mapping. 5-7
In KS 10 memory mapping, 6-3
page tables, 5-7
paper tape reader/punches. 7--4
patlImeters In ALGOL, 8-5
parlty,7-1
passwords. 3·2
PC20 paper tape reader/punches. 7--4
PCS-20 (Project Control System). 9--4
POP-ll SUbsystem. 5-1, 5-7.5-8. 5-10
PE mode, 7·2
Performance Analysis Statistics program. 3-3
peripherals. 2-1
consolelntertace with, "-7
KL lQ...E I/O subsystem and. 5·8
MASSBUS lor. 5-9
mass storage, 7-1-7-2
supported by KL 10-E front-end
subsystem. 5-7
terminals and Interlaces. 7-4-7-6
unit record. 7_2_7_4

physical address space
in KL lQ...Eprocessor, 5-7
in KS10prOC8SSOf, 6-3
physIcal communications links. 10-2
PID (Process Identification Number). "-2
PLI!, CPl and. 8-10
PLEASE program. 3-3
pointers, 4.... , 4-5, 6-3-6....
postpurglng.4-"
power 'allures. automatic recovery after. 3-3
pralo.dlng, 4_"
printers, 7-2-7--4
hardcopy terminals, 7....-7-5
priorities
lor Interrupts. 5-"
lor processes. 4·2
private pointers. 6-3
privileged mode. 5-10
prlvlleges, 3-2
procedures In ALGOL, 6·4-8-5
processes, 4-2
communications by, 4-2--4-3
memory organization and, 2-2
virtual memory and, 4-"
Process Identification Number (PID). "-2
processor modes. 5-2. 6-3
processors. 2-1
aUl{iilary.7-6
console front-end processors. "-6-4-7
Kl1Q...E.5-1-5-10
KS10,6-1-f).5
scheduling lime on. 3-2-3-3
prolesslonal~. 11 -1
program COfItrollnstructlons, 5.... . 6-3
programmable address break. 5-4
programmable asynchronous serial line
multlplel{ers.7-6
programmable verticallormat units (PVUFs).
7-2.7-3
programs
In COBOL, 8-3-8-4
InCPl,8- 10
sharing 01.
program segmentation. 8-7
protection lor Illes. 4-5-4-6
protocol emulators. 10-3-10-5
pseudotermlnals, 7-4

"-6

quadwords.5-6
1 (question mark). 2·2
queue manager. "-1-4·2
R

RDMAIL program, 3-3
record-Ilandling services, 3·1
record InpuVoutput In BASIC-PLUS-2. 8-6
records In DBMS, 9·1. 9-2
recovery. 2·3, 3-3
reg isters
In KL 100E processor,S·"
In KS10 processor, 6·2
lor virutal memory. 4-5
rellablllty,2·3
remote job entry stalions. 10-3
reports. IQL lor. 9-3-9·"
RERUN lacillty, 8·4
resources
accounting statistics lor, 3-3
system manager control of. 3-2

restrIcted mode, 5-10
RH20 Integrated controllers. 5-9
RM03 disk·pack subsystems. 7·1
ROOT-DIRECTORY. 4-8
RP08 disk-pack subsystems. 5-6, 7-1
RSX software. 5·8
RTP20 disk subsystems. 7-1

5
Scheduler. 4-4
scheduling
centralized queue manager for. 4·1--4·2
system manager ,ontrols on. 3-2-3-3
TOPS·20 monitor lor, "-3
SCHEMA.9-1.9-2
scientific applicallons. 2-1
security. 2-3
during diagnostics. 4·7
user authorlzallon for. 3-2
SeU-Malntenance ServIce lor Software. 11·1
sel'-tesl modules, 7-2. 7·3
serial line asynchronous Interfaces. 7·6
serial line multiplexers. 7·8
services, 11-1-11-5
Shared Mode Pointer. 4·5
Snared Page Table (SPT). 4-5, 6-3
shared pointers. 6·3
sherlng
lile syslem for. 4-6
01 memory. 4-3
single-precision Iloating·poInt lormat, 5·3
sIngle synchrooous line Interfaces. 7-6
skip Instructions. 5-3. 8-2-6-3
SLEEP statement, 8-7
software
communications. 10-1-10-5
lor dala administration, 9·1-9-4
process structure 01. 2-2
reliability 01, 2·3
RSX.5-8
support services for. 11·1 (see also TOPS-

20)
software Interrupt syslem, 4-2. 4·3
Software Product Upatea, 11-1
SORT/MERGE utility. 9-4
spoolers
Input. 4-1
oulpul. "-2
SPT (Shared Page Table). "-5. 6-3
SPT Indel{, 6-4
sta tements
In APl,8-8
In tal. 9-3
ststlstics. 3-3
Command Language Processor and, 4-1
STOP statemenl. 8-7
slOtage - see memory
STORE statement, 9-2
string arrays. 8-6
string constants, 8-5
STRING Instructions. 5-4. 6-3
string manipulation. 8-3
string variables. 8-6
subd irectories. 4-6
Sub-Schema. 9·1
superior processes. 4-2
supplies. 11-4
support services, 11 -1-11-5

swapping, 4-4
switches
In ALGOL. 8-5
In batch system, 4·1
system managers, 3-2-3·3
system operators, 3-3
lor bstch processing, 4-1
system programmers, 3·1-3-2
system recovery, 2-3, 3-3
system utilization statistics, 3-3

T
tapes
labelling 01, 4-6
peripherals lor, 7-1-7-2
task-to-task communications, 10-1 , 10-2
terminal drivers, 7-4
Terminal Formal, 8-4
terminal line Interfaces, 7-6
terminals, 7-4-7-8
lor APL, 8-8
consoles and, 4·7, 8-4
In networks, 10-2
remote Job entry stations as, 10-3
time base counter, 5·4
TOPS·20 (operating system), 2·1-2-3,
4-1-4·7
In DECnel conllgurstions, 10-1
Educational Services courses on,
11-2-11·3

Internets supported on, 10-3-10-5
memory assigned by, 5-7
NETCON commands for, 10-3
utility programs with, 3-3-3-4
TOPS.20AN (communications software), 2-3
TOPS-20 assembler language, 8--1
TOPS-20 monitor, 4-3-4-4
TRAFFIC.20 (Transaction Routing and Forms
Formatting In COBOL), 3-1, 9·4
transaction processing, 3-1
trap handling, 5-4, 6-3
TU70 series magnellc tape systems, 7·1-7-2
TU77 magnetic tape systems, 7·1 , 7-2
TV program, 3-4

U
UBR register , 4-5
UNIBUS
In KL 10-E processor, 5·1. 5-7, 5·9-5-10
peripherals attached 10, 7-'
UNIBUS Adapters (UBAs), 2-1, 7-1
unimplemented user operatlona(UUOs), 5-4
unit record peripherals, 7·1-7-4
universal syncronousfasyncronoua
recleVer ftransmltter (USART)
interfaces, 6·4
UPDATE leature, 8-6
user authorization, 3·2

user !!Ie directory, 4·6
user mode, 5-2, 6-3-6-5
User Page Table, 4-5
users, 3·1-3-4
classes of, for lile protection, 4-5
user utilities, 3-3-3-4
utilities, 3-3-3-4, 9-4
with DBMS, 9·2
NETCON, 10-1 , 10-3
V

video terminals, 7-5-7-6
virtual memory, 4-4-4-5
virtual memory arrays, 8--&
VT100 video terminals, 7-5-7-6

W
WAIT statement, 8·7
warranties, lor software, 11·1
word processing, DXf TOPS-20 document
transmission on, 10-5
working set manager, 4·4
working sets, 4-2, 4·4
works paces, In APL, 8·9
WPS·8 word processing sysytems, 10-5

Z
zero, 5-3, 6-2

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