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Document:	DEMO12 Monitor System Technical Reference Manual
Order Number:	DEC-12-MRZA-D
Revision:	0
Pages:	66
Original Filename:	http://bitsavers.org/pdf/dec/pdp12/demo12/DEC-12-MRZA-D_DEMO12_Monitor_System_Technical_Reference_Manual_Apr70.pdf

OCR Text

TECHNICAL
REFERENCE
MANUAL

DEM012
MONITOR SYSTEM

digital equipment corporation-maynard massachusetts

DEM012
MONITOR SYSTEM
TECHNICAL REFERENCE MANUAL

For additional copies of this document, order No. DEC-12-MRZA-D from Prog.rarn ·Library, Dig,ital Equipment Corp., Maynard, Mass. 01754 Price $5.00.

DIGITAL

EQWlPMENT

CO'RPORAIION • MAYNARD, MASSACHUSETTS

1st Printing April 1970
oec-12 - H R..z n -.D

Your attention is invited to the last two
pages of this manual. The Reader's Conunents
page, when filled in and returned, is beneficial to both you and DEC. All comments
received are considered when documenting
subsequent manuals, and when assistance is
required, a knowledgeable DEC representative
will contact you. The Software Information
page offers you a means of keeping up-to-date
with DEC's software.

Instruction times, operating speeds and
the like are included in this manual for
reference onlyr they are not to be taken
as specifications.

The following are registered trademarks of
Digital Equipment Corporation, Maynard,
Massachusetts:
DEC
FLIP CHIP
DIGITAL

PDP

FOCAL
COMPUTER LAB

PDP-12 DEMO USER PROGRAM
DISCLAIMER

The accompanying LINCtape entitled LAP6-DIAL* and DEMO Monitor
System

contains a variety of data acquisition,reduction, manipula-

tion, and presentation programs which operate on the PDP-12A.

All

binaries may be loaded via the DEMO Monitor or with LAP6-DIAL, and
are either self-starting or are started by pressing I/O PRESET and
START 20.

Abstracts describing the operation of each of these

programs are attached.

All credit for these programs belongs, in most cases, to the
original authors.

The only contribution of the current authors

was to convert these programs to run under the DEMO Monitor as a
convenience to PDP-12 users.

The question of responsibility for these programs is a difficult
one.

Obviously the original authors cannot be held responsible

for correct operation of the modified programs in a new machine.
Nor can Digital Equipment Corporation claim to be responsible,
as we do not have adequate descriptions of the internal structure
of some of these programs.

All appear to work.

We would suggest

that the programs be checked out before basing any substantial
conclusions on results obtained with them.

LAP6-DIAL sources

have been obtained for most data reduction programs to allow
program verification and modification.

* Hereafter referred to as DIAL for brevity
i

CONCISE CONTENTS
SUBJECT

SECTION

Introduction

Requirements

Special Considerations

Files

Input/Output .

Core Layout

State Diagram

Flags and Indicators

Loader (LOADER)

10.

Initialization (INITLIZE)

11.

Segment ~ Routines

12.

Segment 1 Routines (SEGl)

13.

DEMO Monitor Messages

14.

Programming Conventions for DEMO User Programs
(DUP's}

15.

DEMO user Program Help Frames

16.

Creating the DEMO Monitor

17.

Operating Procedures

(SEG~)

TABLE OF CONTENTS
SECTION

Introduction

1-1

Hardware Requiremen~s
Software Environment

2-1
3-1
3-1
3-2

4.3

Special Index Considerations
The DIAL/DEMO Index
DIAL/DEMO Tape Storage Allocation
Files
DIAL Directory
DEMO INDEX
DEMO INDEX File

5
5.1

Input/output
Other I/O

5-1
5-1

6
6.1
6.2

Core Layout/Tape Blocks
Initialization Time
Runtime

6-1
6-1
6-1

Monitor State Diagram
States
Transition Tables
Control S-Start the DUP
Control I-DEMO MONITOR INDEX DISPLAY
Control N - Load the next DUP
Control c - Continue
Control H - Help

7'.l""l
7ial

2.1
3.
3.1
3.2
4
4.1
4.2

7.1
7.2
7.2.l
7.2.2
7.2.3
7.2.4
7.2.5
8

8.1
8.2
8.3

8.4
8 .. 5
8.6
8.6.l
8.6.2
8.6.3
8.6.4
8.6.5
8.6.6
8.6.7
8.6.8
8.7
8.7.1
8.7.2
8.8
8.9
0.10
8.11
8.12

Flags and Indicators
I NEXT
STSVD
KSTF, ICHR
TFLG
FOOSWT
I STATE
SVFLO

SVAXO
SVEFS
SVMQ

SVFLD
SVPC
SVLNK

SVAC
TSTATE
ISVPC

INTERRUPT AND TRAP RETURNS
DST.ATE
THISDP
STATE
ZDML
TAPMES

iii

2-1

4-1
4-1
4-1
4-1

7:..2

7-2
7-2
7-2
7-3
7-3
8-1

8-2
8-2
8-3
8-3

8-4
8-4
8-4
8-4
8-4
8-4
8-5
8-5
8-5
8-5
8-5
8-5
8-5
8-6
8-6
8-6
8-7
8-7

PAG:E

SEC'l1ION

Loader

(LOADE~)

9-1

Initialization (INITLIZE)

10-1

11
lLl
ll.Ll
11. L 2.
11.L3
11.1.4
11.LS
11.2
1L2 .. l
11.20L1
1L2.L2
11.. 2. L 3
1L2.L4
11.2.LS

Segment ~ RouHnes

11-1
11-1
11-1
11-2
11-1
11-3
1.1-3
11-3
11-4

~l"elep:r inter

Inte:n:upts
Other In"te:r.r.upt: s

Interrupt Retu:r.ns
Trap Processox Operation
Operate Instr.uction Tr?ipS
OPR5 - Retr:leve
OPR6 OPR7 -

OPRll

Ne:;ct DUl?
E..."'fi.'t th:ts DUP

Extend Intex:r.upt Chain

OPRl2 -

OKST

11.2~1..6

OPR13 ·- KBDA

ll,.2ol.7
ll.2 .. L8
11.2ey2
11 .. 2.2 .. 1
11.. 2 3

OPR14 - TYP
OPRl5 - KBD

12
12ol
12o2
1.. 2,. 3

12 .. 4
12 .. 5
1206
12 .. 7

12 .. 8
12.9
12 .. 9., l

12.10
12.11
12 .. 11. 1
12 .. 11. L 1
12all.l.2

12.11.. 2
12.12
12 .. l.3
13
13. l
13 .. Ll
13. L2
13 .. L3

(~)

Interrupt Handling
Tape Interrupts
Keyboard Interrupts

Tape Inst:i::uctJ.ons
1°ape :tnt:erx:upt Pxocessing
Trap Returns

11-4
11-5
11-5
ll-5
11-5
11-6
11-6
11-6
11-7
11-8
11-10

Segment 1 Routines (SEGl)
12~1
State l Routine - yj?fl~ (Display Error)
12-1
State 2 Routine ~ Y¢2(DispJ.ay DEMO Index)12-1
State 3 Routine ~ Yf03(Get Summary Frame) 12-2
State 4 Uc:)'l..1tine
(DUP Loader)
State 5 ''.!l'¢5 (DISPU\Y summary Frame)

12-2

State 6 Routine - Yp$6 (LOADING XXXXXX)
State 7 Routine - Yfl]7 (Start the DUP)
State 8, 9 & 1!7.I noutine Ylfd (DEMO HELP)
State Changer (11, 12 ~ 13, J.4)
NXSTAT

12-3
12-3

Directory Lookup Routine
Display Subroutine
No:rmal Display .Mode (QANDA compatible)
Text Format
X/Y Coordi.nates

12-4
l.2-5
12-5
12-5

Special Mode for Inde:K Display

DCALL
TAPDSP

12-4
12-4
12~4

12-5
12-5

12-6
12-6

MONITOR Messages
13-1
Messages during Operation of DEMO Monitor 13-1
nn SPURIOUS

IJSJTERRUF.11"

enuNCI~XUUJJ.,:m

D:~TERRUPT 11

"CANNOT FIND PRC.lGlt.l\.M. OR GROUP :JOOOCKX"

13-1
13-1
13·-l

TITLE

SECTION
13.1.4
13.1.5
13 .1.6
13.1.7
13 .1. 8
13. 2
13.2.l

13.2.2

"UNIT n ILLEGAL WRITE-BLOCK mmt
"UNIT n NOT-- SELECTED"
"UNIT n BAD BLOCK mrmn"
"UNIT n- BAD TAPE"
"UNIT n SET WRITE ENABLE"
Messages occurring Anytime
"TAPE OPERATION IN PROGRESS"

LOADING XXXXXX"

13-2

13-2
13-2
13-3
13-3

13-3
13-3
13-3

Programming Conventions for DEMO user Pgms.
DEMO user Program Instruction Restrict.
Special Functions Register
DEMO user Program (DUP) Core use (to 6K)
DUP Start Conditions
DUP Use of LINCtape (SCRATCH.)
DUP Write Protection
Tape Extended Operations Register
NO PAUSE TAPE operations
Operate Instruction, OPR usage
RETV (OPRS)
NEXT (OPR6)
EXIT (OPR7)
XCHN (OPRll)
OKST (OPR12)
KBDA (OPR13)
TYP (OPR14)
KBD (OPR15)
DUP Instruction Restrictions

14-1
14-1
14-1
14-1
14-1
14-2

DUP TEXT Files (Summary & HELP Frames)
DUP Summary & Help Frame
Assembly & Storage Procedure

15-1

16-l

16.4
16.5

Creating a DEMO Monitor Tape
Cross Segment References
Assembly
The DEMO Monitor Binaries
"PIPing" the Pieces Together
Talk Balloon
DEMO INDEX Creation

17
17.1
17.2
17.3
17.4
17.5

Operating Procedures
Loading - Two tapes
Loadlng - one tape
Restarting
Terminating
Error Conditions

14
14.1
14.2
14.3

14.4
14.5
14.6

14.7
14.7.1

14.8
14.8.l

14.8.2
14.8.3

14.8.4
14.8.5
14.8.6

14.8.7
14.8.8
14.9

15
15.1
16
16.1

16.2
16.3
16.3.1

14-2
14-2
14-2
14-2
14-2
14-3
14-3
14-4
14-4
14-5
14-5
14-5
14-5

15-1
16-1
16-1
16-1
16-l
16-2
16-2

17-1
17-1
17-1
17-1
17-2
17-~

1. INTRODUCTION

. 1-1

2.0

Hatd0~~~

Requirements

The monitor will run on a basic PDP-12A.

Use is made of the

VR12 display, the LINCtape control and two units, the console '!Bletype
and 2K of the basic 4K memory.

Options not included in the PDP-12A

basic system are not required, but up to,6K of core may be used by
the DEMO User Programs

(DUPS ).

The DUP loader will load 6K pro-

grams.
The monitor includes a provision for the
~r~~
~rap~

de~ices

~hich

handlin~

are not part of the basic system.

of interrupts
(See para-

8.1 for a description of this provision.)

Software Environment
~he

monitor is entirely self-contained and requires no

additional software for the operation of the s:ystem, except DUPs
~~ich

must conform to certain core restraints and not use certain

i~strcctions

,;_

directly.

(See paragraph 14.0)

2 - 1
Teletyp8 is a resistered trademark of Teletype Corporation.

3.0

Special Tndex Conside~ations
The DEMO System contains the DEMO Monitor in blocks

Bloc~

20 is a

duplic~te

~-17.

of the DIAL Index,bloQk 346,and is located

in block 20 so that the DEMO Monitor needn't go all· the way up to

346 to get DIAL's Tndex, thus saving significant amounts of tape
3;·h1fflin9 time.

DIAL and the ~EMO !!_ser !rograms (DUP5')

are in

the rest of the tape; along with some Utility programs and sources.
A special entry in the DIAL Index must reserve blocks 0-20,
1:J3 -1s2 for the DEMO.

Al though no special format is required

for this reservation, the method suggested is an entry in the
DIAL Index as indicate~ in paragraph 3.2.
3.1

The DIAL/DEMO Index
~7ever

l 3

DS~·10

use a period at the beginning of a file name unless it
TJ ser

Progr amo

3 -

3.1

DIAL/DEMO Tape Storage Allocation
REQUIRED FOR
DIAL
SYSTEM

REQUIRED FOR

DEMO MONITOR
SYSTF.M

BLOCK
270

DEMO
MONITOR

23
24

FILETYPE

'3d
340-

103

MORE DIAL
USER

367
370

LKS

634

FILES

635

DIAL USER
FILE SOURCES OF
DEMO MONITOR
AND ASSEMBLED
BINARIES OF
DEMO MONITOR
SUBPARTS

DIAL EDITOR
SOURCE
WORK AREA
100 BLOCKS

153
BINARIES
OF

EXECUTABLE

QEMO
USER
PROGRAMS
(DUPS)

~.....
~26_7~-~~~~~-;/

NAME

-........,...-SOURCE
BN BLKS

LOADER.
SEG0J-J.
SEGIJ-4.
INITI..IZ·
GREE TIN.

BALLOON.
SEG84-4.
DMOINDX.
Q AND A.
.oA-DTST
.DDATA12
·DMAGSPY

DEMO

MONITOR
SYSTEM
PROPER

2-4

.OF'RQANA
.DOI AL
.EF'REQJ2

.EWAVES

50
52
53

.EB.BALL
.EBASMEM

.F'SOLACE
·F'MUSIC
eFKALEIO
• FORAW

.F'ECHASK
.FSPCWAR

• TOAYCOM

45
46

54
55
56
57
61

63
66

2
4
2
2
1
2
2
1
I
I
l
l

2
2
3

• TCLOCK

67
71

l
2
l

SCRATCH.

103

50.

• TSTPWCH

GREETING
INDEXSRC

263

DIAL USER

FIL£S

DIAL
INDEX
MORE
DIAL
SYSTEM

347
350

102

DIAL
SYSTEM

HELP l:'RAMES
FOR ALL
DUPS

152

470

DIAL

--,00_...,__...._
_____
~2TI
FREE

BINAR¥
SUMMARY
AND

DEMO
SCRATCH
AREA 50

NONE OF THESE FIIES
REQUIRED FOR DIAL OR
DEMO USE.DIAL USER
FILES DELETABLE
BLOCK
FILETYPE

777

467

BINARY.
SN

0
t

BU<S
I
3

10
11
12
I7

I
l
5
I

20
22

2
2

l 65

37
153
72
163
170
173
176

6
10
11
2
3
3
3

201
206
210

5
2
6

216

220

22cJ
226

244

250
256

6
5

DIAL~V2

DIAL
UTILITY
& MISC.
USER

PIP
EXaPROG•
AD DEMO

FILE

DEMO
ONITOR
BINARY&
SOURCES
M·.

s22·

MARJ<12

524
526

511
470

7
21

520

614

BINLOAO
L8SIM

535

540

CONVERT

543

3
5

F'OCAL8K
F'OCAL4J<

550
573
617
637
660

23
21

717
763
771

CAROLS
LOADER

INITLIZE

641

2
17

SEG0

663

SEGl
BALLOON

725

04-01-70

527

635

11
2
3
6
5

DEMO USER PROGRAMS
SOURCE AREA CONTAINS
HELP FRAMES AND

TIU!: BINARY.AREA CONTAINS
THE ACTUAl PROGRAM

776

3 -

4.0

4.1

DIAL Directory
The DIAL dixectory is assumed to be as specified:

each entry

is eight words consisting of eight stripped 6-bit ASCII characters
abd £our words of block information, with all unused words filled
with 5757 8 •
tape.

It is assumed to be on blocks 346 and 347 of the DEMO

The DEMO Monitor doesn't use 346 or 347 directly, but

rather a copy of the DIAL directory, block 346, copied into block 20
of the DEMO tape u~ing PI~.

Note that a change to the DIAL directory

then will not af feqt the DEMO INDEX unless block 346 is again
modified.
,PEMO Index

4.2

The DEMO Index is created from the DIAL Index copy in block 20
during initialization and is written on tape block 17.

The last

57 8 words of the directory are part of the instruction trap handling
routines.
Each entry in the DIAL Index for which the first character is
56 8 ('. •) is .copied into the DEMO Index.

Only the first 30 entries

with •.• as the first character are so copied -- the rest are
ignored.

The entries in the DEMO Index are then sorted by the

second character of the entry.
Filler characters (77 8 ) in the name portion of each entry are
converted to spaces.
4.3

DEMO Index File
The DEMO Index File is a display buffer which is created

during initialization and written-on_tape block 16.

It consists

entirely of display data in a special format peculiar to the DEMO
Monitor, see paragraph 11.2.

4 - 1

s.o

Input/output
The DEMO Monitor is cognizant of only the console Teletype

and the LIN~tape controller when it handles interrupts unless
the DUP requested an interrupt chain extension.
14.8.4.

See paragraph

All input to the monitor normally comes from the Tele-

type or from the tape controller.

All output normally goes to

the Teletype, the VR12 display, or LINCtape.

A-D input comes

via the DUP.
The use of tape units is important.

In general, tape 1,

if available, will always be in the vicinity of blocks 16 and
17, the display index and index respectively.

All DUPs are

loaded from tape ~.
5.1

Other I/O
I/O with other devices can only be handled by a ll>lJP and if

that device generates interrupts, the interrupt chain extension
feature will have to be used.

5 - 1

6.0

Core Layout/Tape Blocks

6.1

Initialization Time
Tape Block

CORE

0 ---377

Interrupt and trap handler

400 - 777

Interrupt and ·trap handler

1000-1377

Interrupt and trap handler

1400-1777

Not used

2000-2377

Monitor State routines,

2400-2777

subroutines, and

3000-3377

messages

6-7

4000-4377

Initialization (INITLIZ.)

4400-4777

Initialization (GREETIN.)

5000-5377

DIAL Index

5400-5777

Not used

6000-6377

First half of

6400-6777

Talk Balloon

DEME.l Index ~Second Half of
(during sort)
(~£tier sort~
Index Display
Talk Balloon

7000-7377
7400-7777

6.2

(copied from block 20)

11/14
17/15

Runtime
- 377

Interrupt and trap handler

400 - 777

Interrupt and trap handler

1000-1377

Interrupt and trap handler

1400-1777

Tape Buffer-Index, display index, sununary or Help

2000-2377

state routines, messages

2400-2777

state routines, messages

3000-3377

Subroutines

3400-3777

Subroutines

4000-17777

Demo user Program (DUP)

6-1

User specified

7.0

Monitor State System
Changes of M.onitor status when a control key is struck are

handled through a state cha.nge table in the Monitor.

The table

contains entries for each state and each control character such
that the next state can be determined by existing state and
control characters.
7.1

States
The following are the states of the DEMO Monitor which can

be in effect.

Error Display or Monitor Help.

Display Index and accept as input the name of a DUP.

Load DUP Sununary frame.

·4.

Load a DUP.

Display the DUP Summary frame and wait for Control s.

Set state 5 to not wait for Control s and go to state 4.

Execute the DUP(using the saved state if one exists).

Display DUP Help frame

9.
10.

Display DUP Help (Three states because of differing state
transitions)
Display DUP Help

11.

Select

12.

If a state is saved, restart the current DUP at the saved
state.

13.

If the

14.

If a DUP is selected, load it.

next DUP in same group and load it.

DUP is loaded, start it.

7 - 1

7.2

Transition Tables
There ate separate transition tables for each control character.

The new state is a half-word entry in the table.
Note that table entries are in octal, but refer to decimal
state numbers •. This can lead to some confusion, so care should
be taken in this area.
Control s - Start the DUP

7.2.1

The transition table for Control s is tagged TS in bank ~.
Its entries are:
Existing Entxie s

New State

1
2

14
13

3
6
7
6
6
6
7
6
11

4
5
6
7
8
9

10
11
12
13

12
13

Control I - Go to DF.MO Monitor Index Display

7. 2.2

Since every entry in the table would be a 2, no table is
required.

In place of a table address, control I's entry is a

-2 which is properly interpreted as a transition to state 2.
7.2.3

Control N - Load the next DUP

As in 7.2.2, no table is required.
is a -13 8

or new state 11 10 •

7 - 2

The entry for Control N

Control c - Continue Current Program

7.2.4

The transition table for Control C is tagged TC in block ~.
Its entries are:
Existing State

New St~te
12
12

1
2

3
4
5

6
7

5
6

8
9

6
7

10
11
12
13
14

Note:

11
12
13

14
A zero entry indicates that no state transition is to

take place.
7.2.5

Control H - Help
The table for control H is tagged TH in bank ~.

Its entries

are as follows:
Existing State

New State

3
4
5
6
7
8
9

1
8
9
8

10
1
l

10
11
12
13
14

1
1

1
l

Note: Any transition to state 1 will cause "MONITOR HELP"
to be displayed. Error displays are handled in a special manper.
7 -

8.0

Flags and Indicators
The following flags and indicators may be of interest for

debugging or adding any changes to the Monitor.
NAME

BANK

LENGTH

I NEXT

ST SUD

8 mode
address
Flag

KSTF

Flag

ICHR

Data

TFLG

Flag

0 =Printer not busy
1 =Printer busy

FOOS WT

L.Inst.

Contains a jump to one of
several appropriate routines
to handle tape interrupts.

TA PINT

Same as FOOSWT

I STATE

109

TSTATE

109

DSTATE

108

l. overflow state
2. AXO register
3. · SF register
4. MQ
5. Fields
6. PC
7. Link & Mode
10. AC

SPECIAL VAWES
fl::: No extension
fl:: No state saved

7 =State saved
fl: No keyboard character
available.
1 ::: Char. available in. ICHR.
last char. rec• d. (ASCII)

Interrupt state
diagram
below

Trap state
Saved DEMO state

(SVFLO)
(SVAXO)
(SVEFS)
(SVMQ)

(SVFLD)
(SVPC)
(SVLNK)
(SVAC)

THISDP

Laddr.

Pointer to DEMO INDEX entry
for current DUP.

STATE

Data

Current state number

ZDML

Flag

0-DUP · is not loaded
1-DUP is loaded

TAPMES

L
addr.

8 - l

Location of message to be
displayed during tape op.

8.1

!NEXT (used by OPRll)
The 12-bit PDP-8 address in INEXT is placed there by an OPRll.

The call is:
OPRll
-PMODE

ROUTINE NAME (a 12-bit address of the interrupt service
LMODE
routine located in the current DUP using OPRll).
or any equivalent sequence.

(See paragraph 14.8.4 and 11.1.4)

once specified, the extended interrupt routine will be executed

for eac::h interrupt from a device other than LINCtape, key-

board, or TTY printer.

The Monitor fields and handles all interrupts

from those devices.
Obviously, the above code sequence can only be executed from
within the DUP.

However, the extension routine remains in effect

when DUP execution is suspended or terminated by any means.
The extension routine will be retracted only when a new DUP
is about to be loaded, the same DUP is being reloaded, or the
following code sequence is executed. care should be exercised in
user programs so as not to leave OPRll on.

OPRll

8 .. 2

STSVD
STSVD is a flag which indicates whether DSTATE contains a

valid DUP state or not ..
If {STSVD)

= JI, DSTATE does not contain a valid state.

If (STSVD)

7, DSTATE is a valid state.

No other values will occur.

8 -

8.2

STSVD (continued)
Whenever a trapped instruction occurs, or whenever a state

change is dictated by a control character, DSTATE is set to the
ptoper values and STSVD is set to 7 by the subroutine COPY.

DSTATE.

thus represents th~ state to which control should be given to
continue DUP execution where it was interrupted.
In the case of trapped instructions, the PC value in DSTATE
always indicates the address of the ~ctual instruction which is
trapped.

Therefore, that instruction will be re-executed if DUP

execution is suspended during

the trap process and later resumed.

8 - 3

8.5

FOOSWT (also referred to as TAPINT)
This location is actually the first word of the routine which

is executed when a tape interrupt occurs.
JMP to

It contains a LINC-mode

an appropriate portion of the tape interrupt processor~

further discussion of this switch will be found in section 11.2.2.1.
ISTATE

8.6

!STATE is a group of 108 locations used to preserve the state
of the machine when an interrupt occurs.

8.6.1

SVFLO

SVFLO is the first word of ISTATE.
the, interrupt occurred,

If overflow was set when

(SVFLO)::; 7776 (-1), otherwise it is fl}.

SVAXO

8.6.2

SVAXO contains the tape extended operations register which
was ih effect at the time of the interrupt.
SVEFS

8.6.3

SVEFS contains the special functions register which was in
effect at the time of the interrupt.
8.6.4

SVMQ contains the full 12 bits of the MQ at the time of the

interrupt.

'!'he MO is retrieved by the follow~ng coqe:

QAC

ROL 1
QLZ
ADD ONE

8 -

8.6.5

SVFLD

SVFLD contains the fields in effect before the interrupt
occurred.

SVFID is always saved in LINC mode via the IOB: RIB

instruction.
SVPC

8.6.6

SVPC contains either a PDP-8 mode address or a LINC-mode JMP
to the place where the interrupt occurred, depending upon the mode
at the time of the interrupt.
8.6.7

SVLNK
SVLNK contains only 2 significant bits.

the link at the time of the interrupt.
8.6.8

Bit 0 is the state of

and bit l is the mode if set.

SVAC
SVAC contains the contents of the AC register at the time of

the interrupt.
8.7

TSTATE
TSTATE is similar to !STATE, but it indicates the state at the

time a trapped instruction occurred.
8.7.1

ISVPC
ISVPC contains a LINC-mode JMP to the conunand which caused

the trap rather than the next instruction in sequence.

It is

incremented just prior to returning to the state from which the
trap occurred.
8.7.2

Interrupt And Trap Returns
Traps cannot occur in PDP-8 mode, but all flags are properly

set so that conunon returns from trap and interrupt are possible.

8 - 5

a.a

DSTATE
DSTATE is a copy of either !STATE or TSTATE.

The copy is only

made if
l.;

·a ttapped instructiion is being executed, ~

a control character which causes a state change has been
received, and

DSTATE does not already contain a saved state (see STSVD,
paragraph 8.2.)

8.9

THISDP
THISDP is a pointer to the DEMO .INDEX entry for the currently

loaded DUP.

When the Index is in a>re it is in quarter 3 of seg-

ment ¢, therefore, THISDP contains a value between 3400 and 3777.
It is always referenced from

segment l

(DFr~).

STATE

8.10

STATE contains a unique number for each of the various Monitor
routines.

It is required in order to determine which routine

should be entered when a control character is struck.

To illustrate

the problem, it should be noted that Control !! can cause either DEMO
Help or Monitor Help to be displayed, depending upon whether
it has been struck once before or not.

(This is a simplification.

The actual state transitions for each control character are described in section 7.)

Since Monitor Help and DEMO Help are dis-

played by different routines, some means of knowing what is
currently going on is required.
STATE always contains a value between l and 168 •
of each value is described in section 7.

8 - 6

The meaning

8.11

ZDML is a flag which indicates whether the DUP is loaded and
is a "clean" copy or not.

It is set to l when the DUP is loaded

and is reset to ~ when a new DUP is selected or when the DUP
execution is begun.
TAPMES

8.12

TAPMES is a word which contains the address of a message to
be displayed while tape operations proceed under trap processor
control.

Generally, TAPMES is set to the address of the message

"TAPE OPERATION IN PROGRESS."
This feature is not available to the DUP.

8 - 7

9.0

Loader (LOADER)
The loader res.ides on block JI -of the DEMO t_ape.

Its only

function is to load the entire DBMO Monitor and initialization
program

(INI~LIZE).
I

The Loader first re-reads itself into se9Iiient 2, quarter 3 and
transfers execution to itself in that location.

It then proceeds

to load blocks l through 7 from tape into segment $6, quarters /(1,
1, and 2 and segment 1, quarters JI, 1, 2, and 3.
The next two tape blocks, lfi/
2, quarter ~ and quarter 1.

and 11, are loaded into segment

These are the initialization routines.

Block 11 is loaded into segment 3, quarter 2 as well as segment 2,
quarter 1, since the last several words of block 11 are a part of
the index display block which will be generated in segment 3,
quarter 2.
The "BALLOON" generation information is contained in tape
blocks 12 through 15.

Two of these are loaded into segment 3,

quarter JI and quarter 1, leaving the rest until after initialization
is complete.
Finally, the index block, 17, is read into se(Jment 3, quarter
3 where the new index will bE! created.

Tl;le fodex block contains

a routine used only when the DEMO Index is in core.

9- 1

Initialization (INITLIZE)

10.0

Initialization runs entirely with interrupts off.

Its function

is to create the DF.MO Index and Index display and to write them both
on tape, then to pause with the message "TALK TO ME" displayed.
During

~nitialization,

all tape operations proceed in no-pause

mode with the message "INITJ:ALIZATION IN PROGRESS" displayed for
the duration of the tape operation.
First, the duplicate DIAL Index is read into core quarter 2,
segment 2.

While the tape is positioning, it is constantly observed

to assure that progress is being made toward the DIAL Index copy
in block 20.
Once the DIAL Index is in, it is scanned for entries which

begin with a period (". ") and all such entries am copied into
the resident index.

A maximum of 30 entries can be copied into

the resident index.

All filler characters in the DIAL Index (77 8 )
are converted to trailing spaces in the resident index.
The resident index is then sorted by the second character of
each entry, 30 passes are required to assure that the resident
index is in proper ordero

10 - 1

Segment. fl Routine~

11.0

(SE:G~)

The routines in segment fl consist almost entirely of interrupt
and trap handling.

This narrative is intended to describe the

operation of those routine$ while the code is followed in the
listing.
Interrupt Handling

11.l

Interru.E>t handler entries for PDP-8 mode interrupts
(location l) and LINC mode interrupts (location 41) are both
provided.

Their paths are only separate for a short time.

each entry, the AC is saved (in SVAC), and the PC is saved from
location fl or 4/3 as appropriate.

In LINC mode, the saved PC is

set to a JMP before it is saved.

Processing continues at INTSAV,

with a clear AC if the interrupt occurred in LINC mode, and with
at least a high order bit in the AC if the interrupt occurred in
PDP-8 mode.

This bit is preserved with the link and is used to

effect a proper return from interrupt processing.

All other

status is saved in ISTATE by the subroutine SVSUBl.

The interrupt

processor then proceeds to check flags and execute the appropriate
routine.
11.l.l

Tape Interrupts
If tape interrupts are enabled and if the f la9 is detected

with a STD, the interrupt bas come from the tape control.
is the beginning of the processing routine.

A further discussion

of tape interrupts will be found in paragraph 11.2.

11 - 1

TAPINT

11.1.2

Keyboard Interrupts

If the keyboard flag is up, the keyboard interrupt processor
·is executed.

The character is read from the keyboard buffer and

the keyboard flag is cleared.

Note that no check is performed

to see if the previous cha~acter has been delivered via KBD or
KBDA operates, so that the new character overlays the old char~

and the old character is lost.

An internal flag, KSTF, is set to 1 to indicate that a new
character is in.
The new character is then matched to a table, KCTAB, to see
if it matches any entry.

The last entry of the table is the

character itself, so a match is bound to occur.
Alternate words of the table indicates what state change is
required as follows:
1.

Positive entry - the address of a state transition table,
shifted left 1 bit and decremented by 1.

Negative entry - the next state number.

Negative zero entry - no state change required.

In the event that a state change is indicated, the flag KSTF
is cleared.

The subroutine COPY is called to save the DUP state

if it has not already been saved and if, in fact, the DUP was
executing when the interrupt occurred.
state changer (segment 1).

Control is given to the

See paragraph 12.9 for further pro-

cessing.
11.l.3

Teleprinter Interrupts

If the interrupt was neither from tape nor keyboard, the
teleprinter flag is tested and, if it is up, it is cleared and
the flag TFLG is cleared.
11 - 2

11.1. 4

Other Interrupts

If none of the above flags is found,the_ interrupt extension
routine, if any, is executed.

If none is present, or if the

interrupt extension routine does not find any flags, processing
is transferred to ISER~.

otherwise control is returned via

RETB (see paragraph 11.1.5).
At ISERfl, a power clear is given and a test is made to see
if the interrupt is still present.

If it is not, the message

"SPURIOUS INTERRUPT" is displayed.

Execution may be resumed with

Control c.
If the interrupt did not clear with power clear, the message
"UNCLEARABLE INTERRUP'l"' is displayed.

No return is possible and

the DEMO Monitor will have,to be restarted.
11.1.s

Interrupt Returng

Return from interrupt processing is thsough a routine called
GO via RET or RETB.

Each status is restored and interrupts are

turned on before returning to the appropriate place in the appropriate mode.
I

11. 2

Trap Processor Operation (See paragraph 14.S).•
The trap processor is entered at location 14jtl in segment fl.

The status is saved in a manner similar to that found in the
interrupt processor, except that 1Stl8 registers at TSTATE are used
instead of those at ISTATE.
Several instructions within the trap processor are modified
as part of trap entry as follows.

·u - 3

11 .. 2
Tag

contents
changed to

RPS •

LIF n " .. n was the IF at trap time
LDF m o "'m was the DF at t~ap time
LDF n

RP5·J-l ..
ITl ..

LDF n
JMP y

RP2 ....

RP5·t2

y is the address of the
tr.apped instruction

LINS

RP¢ • •

LINS

The trapped instruction
'!lhe next word
The addxess of the second
word after the trapped
instruction (with two high
m::de:t bits set) .,

SVP2~

SVP3 ...

t~apped instruction
., rrhe thixd word

The second word after the

Note also that the PC in. the saved t:rap stat(~ points to the

instruction which caused th!9 t:11:ap xathex than the next instruction
in sequence.
'fhe subroutine COPY :Ls

called when a txapped instruction

al'V?~1ys

is encountered ta save t:he st!i!tG of the DUPo

It is alwaxs possible

to be inter:t:uEted O!-lt oJ: ~j~:ii~a,l?~J?!,Ocesso:t~ut nevex to be trapped
out of the

int~J~r~.t ~~o<::e~so:~.,

HEHlce o the DUP state must be saved

before :i.nte:r:r.upts are enal~lecl.,
11. 2. l

It is now determii:"1ed whether the trapped insit:xu.ction is a tape
instruction or an upe:t:Clte,,

j,t

:J.s an opexate, a JM.P to the appro-

priate routine ,,;J,~ a JMJ? table at IOP.:RT is geme:r.aited and after
enabling :lnterruptsu the

:t~out:l.:ne

is ente~ea..,

The discussion of

11 .. 2 .. Ll
The routine fo~ Ol)R 5 is no-1: xe~id.ent in segment

of the DEMO INDKK on tape block 16..
neededr hm>1ever, oocause OPRS is

¢.,

I·t is part

:r.i:t is always in core when

nev~Ii:E:

n = 4

it is

called within the DEMO Monitor,

11.2.1.1 OPRS - Retrieve (continued}
and because the OF.MO Ihdex is read into core before DUP execution
can commence or continue it,is available for DUP use.

The routine at IRETV moves the parameter into ZPNAME (see
paragraph 12.10) and calls the directory lookup routine which
is in segment 1.

The call is indirect.

If the search is success-

ful, the last four words of the directory entry are copied from
the DEMO INDEX into tae last four words of the parameter area and
the routine exits via XP2 (see paxagraph 11.2.3).
11.2.182 OPR6 - Next DUP
The routine for OPR6, at INDM, calls the state changer in

segment l with a new state value of 138 •

(See paragraph 6. 7 for a

description of that state~
11.2.l.3 OPR7 - Exit this DUP
The routine for OPR7, at IEDM, calls the state changer with
a new state value of 2. ( See paragraph 12.2 for a description of

the operation of that state.)
11.2.l.4 OPRll - Extend Interrupt Chain
The routine for OPRll, IXCHN, mo"es the contents of LINS+l,
which is a copy of the word following the trapped instruction, to
!NEXT.

11.2.l.5

It then returns to the program vJ.,a XP2 (see 11.2.3).

OPR12 - OKST

The routine at Ia<ST tests the hidden keyboard flag and
returns to either the next instruction in sequence or the following
instruction via XPl or XP2, respectively.

11 - 5

11.2.1.6

OPR13 - KBDA

The operation of IKBDA is inextricably related to the routine
IKBD, and is
11.2.1.7

d~scribed

along with IKBD in paragraph 11.2.1.8.

OPR14 - TYP

The routine ITYP retrieves the saved AC from TSTATE and,
after waiting ror the teleprinter to be free, sends the character
to the teleprinter.
11.2.1.B

Return to the DUP is via XPl. (See paragraph 11'.. 2. 3)

OPR15 - KBD

The operation of IKBD and IKBDA are closely linked.

In both

cases, if no character has been received from the keyboard, and
if the "I" bit in the instruction is off, return is made via
XPl with the saved AC cleared, but if the "I" bit is on, control
is retained until a character is received.
The important locations for the keyboard input routines are
CASE, LNCODE, and ICHR, the actual full ASCII character received
from the keyboard.
contains a

For the moment it may be assumed that CASE

f3.

Once a character is received from the keyboard, control
passes to KBDT where CASE is tested.

If CASE is non-zero, then
I

LNCODE contains the character to be returned to the calling program;.
Since CASE is zero, control is passed to KTRNS.
At KTRNS, the trapped instruction is examined.

If it is an

OPR13 - KBDA, ICHR is placed in LNCODE, CASE is cleared, the
character is echqed and a line feed is also typed if the received
character was a carriage return.

11 - 6

11.2.l.8

OPRl5 - KBD (continued)

Finally, LNCODE is placed in the saved AC, KSTF is cleared
and control is returned via XPl.
If the trapped instruction was OPRlS (KBD) then the input
character is taken apart and reassembled until the LINC code for
the character is in LNCODE and CASE is set to ~ if no case code
is required, or 23 8 if it is required.
echoed, CASE is examined.

After the character is

If it is non-zero, it is placed in the

saved AC and control returns via XPl.
On

the next call to IXBD, CASE will be non-zero, so it will

be cleared, KSTF will be cleared, and LNCODE will be transmitted

back to the calling program.
11.2.2

Tape Instructions

If the trapped instruction is a tape instruction, further
Monitor initialization is required.

In case of error, the "UNIT n"

message is set to indicate which unit is being operated on.

The

unit number may be any octal digit.
The tape trap enable pit in ~he extended functions register
is cleared, but no e~her bits are disturbed.

The flags MTBP and

WRTF are cleared.
Depending upon the instruction involved, the flags MTBF or
WRTF may be set again for MTB instructions or write instructions
respectively.

Further, the first and last blocks of WCG instruc-

tions or the block for WRC and WRI are checked for the range
103-152 (50 blocks) (see paragraph 13.1.4).
The tape interrupt switch is set for a first interrupt,
and the timer is set so that instruction time can begin.

Finally,

an MTB conunand is generated and issued to the appropriate tape

11 - 7

·11.2.2

Tape Instructiogs (continued)

unit with mai.ntenance mode and

no-pause on.

The maintenance

commands are used to determine whether the unit is selected and,
if necessary, wtite enabled.
Since the remainder of tape trap processing occurs on an
interrupt basis, the display routine in segment l is now called.
It is first necessary to save location ~ in segment 1 since it
may be that the trapped tape instruction was in that segment, and
location ~ might be vital.

Also, a block count error counter is

set to -3 at this time.
11.2.2.l

Tape Interrupt Processing

The remainder of activity in the tape trap handler occurs
with tape interrupts.

At the first tape interrupt, the switch

FOOSWT is found to be a JMP FOOS.

At FOOS, the flag MTBF is

checked and if the trapped instruction was indeed an MTB, control
is immediately relinquished via TPX'l'.

The action at TPXT is

described below.
If the instruction is not an MTB, the action on the first
interrupt is merely to change FOOSWT to a JMP FOOSl and to reset
the timer for instruction timeout.

The MTB instruction generated

above is again executed and control is returned to the display
in the normal manner for interrupts.
The second interrupt causes a transfer of control to FOOSl.
Here, a subroutine,TACTST, is executed to read the TAC (Tape Accumulator) into the ACe

The TAC contains the number of blocks the tape

is away f:rom the destination block at the present time.

11 - 8

11.2.2.l

Tape Interrupt Processing Cgontinued)

TACTST detects the condition that the TAC is zero, but for
this discussion, let us assume that the TAC has a non-zero value.
Back at Foos1·, this value is made negative if it is not already
negative, and stored in a word tagged OTAC.

FOOSWT is set to a

JMP FOOS2, the timer is reset, the MTB is again executed, and
control is returned in the normal manner for interrupts to the
display routine in segment 1.
The third and subsequent interrupts cause a transfer of
control to FOOS2.

At FOOS2, the subroutine TACTST is again

executed, but this time the TAC is made positive, progress was
not made during the last tape oper~tion and a tape error is
indicated.

However, the tape has "three chances for.this kind

of error before the error is detected.
Assuming all is well, the new TAC is now made negative
and stored at CYrAC. The timer is reset, the instruction re-executed,
and control is returned as above.
When TACTST detects that the destination block has been
reached, it does not return as a subroutine, but proceeds to
execute the actual tape command in place.

To execute the conunand

in place, a LIF fl is placed in the location following the two
word tape command and a JMP TWAIT is placed in the following
location.

Then the command is executed.

which were saved earlier

At TWAIT

the two words,

are restored, FOOSWT is set to JMP TP}{T,

the timer is reset, and control is returned to the display
subroutine in segment 1 via normal interrupt procedure.

11 - 9

11.2.2.l

Tape Interrupt Processing (continued)

When the last interrupt finally comes in, the routine at TPXT
restores segment 1, location ~' sets FOOSWT to JMP FOOl to ignore
further interrupts, and returns via XP2

a~y

(see paragraph 11.2.3) rath~r

than via the interrupt procedure.
11.2.3

Trap Returns

The saved PC TSTATE is the address of the actual instruction
which caused the trap.

All trap returns must increment this

address once or twice, depending upon the instruction, before
using it to return.

This incrementing is done at XP2 for incremen-

ting twice and at XPl for incrementing once.
XP2,

The code is as follows:

PDP
PM ODE

ISZ ISVPC
LMODE

XPl,

PDP
PMODE

ISZ ISVPC

Note that the instruction PDP at XPl is sometimes executed in
PDP-8 mode.

This is of no consequence

because the instruction,

when interpreted as a PDP-8 mode instruction, is an "AND 2 11 ,

and

the accumulator contains nothing of value at this time.
once the saved AC is incremented, the return is much like the
return from interrupts, except that STSVD will be cleared if the
state is 7.

11 - 10

12.0

Segment 1 Routines (SEGl)
The routines in segment l are the state routines and several

subroutines.for use by the Monitor.

This description is intended

to be used in conjunction with a listing of the SEGl routine.
12.1

State 1 Routine ~ Ygl

(Display Error)

The state 1 routine is used to display all error messages.
As such, it is :Sometimes entered directly from another routine
with STATE set te some value other than 1.
The contents of the AC at the time of entry is the number
of a message in the table Y{41TAB.

This value is saved in Y{41D{4.

If Y¢1 is entered from a state transition, the AC will be

clear on entry.

The message thus invoked is the Monitor Help Frame.

Error numbers greater than 5 are tape error messages.
Therefore,it is necessary to display the message "UNIT n" preceeding the display of the numbered message.
12.2

State 2.. Routine

- y{42

(Display DEMO Index)

The Display I.ndex routine Yjt12 is always entered h·-om the
State Changer via a state transition.
After reading in the Display Index, the 4 word variable
ZPNAME is initialized and the Index is dis.played.

The mes.sage

"TYPE IN PROGRAM· OR GROUP" is a part of the Display Index and is
always at the same place within the Index block.
__/
If a character is entered from the keyboard, this character

is stripped of its two high order bits and placed in ZPNAME in
the next available character position.

If the entered character

is a carriage return, the name constructed in ZPNAME is looked up
in the DEMO IND~, trying each possible group letter until it is
found or the possibilities are exhausted.

Exhausting the possi-

bilities res.ults in a call to Y¢1 with 4 in the AC.
12 - 1

12.2

State 2 Routine

Y~2

(continued)

If the entry is found, THISDP and the variable DEMON (3 words),
BKSM, BKNM, and BKSB are set from the DEMO INDEX.

Then state 3 is

entered via a callto the State Changer.
State 3 Routine - yg3

12.3

(Get Sununary Frame)

The state 3 :r:outine intitializes the Monitor flags INEXT,
STSVD, and ZDML.

State 5 is set to wait for a Control s from the

keyboard, and the first block of the DUP
the buffer area in segment ~.
Summary Frame.

HELP

file is read into

This first block contains the

When it is read in, TAPMES is set to cause the

Summary Frame to be displayed during tape operations, and state 4
is entered via the State Changer.
12.4

State 4 Routine The loader.,

Y~,

from tape into core.

(DUP Loader)

is designed to load DIAL format binary
It is incapable of loading into the lower

half of t.he first 4K memory bank, which is the Monitor area, but
will load the remainder of up to SK of memory properly.

When the

load is completed, state 5 is entered via the state changer.
State 5 Y~S

12.5

(Display Summary Frame)

The State 5 routine functions in either of two ways, depending
upon the state of the switch Y~5.

Y~S

contains either a NOP or a

JMP Y¢5A.
If Y¢5 contains a NOP, State 5 simply displays .the summary
Frame.

When a Control s is typed, the interrupt handler will in-

voke the state Changer to cause a transition to state 7.

12 - 2

12 .s

state 5 Yfi!S (Display Summary Frame)

(continued)

If Yfi!S contains a JMP YfdSA, the Index is read into the
buffer area in

SEGfl, quarter 3, and State 7 is entered

(see

paragraph 12. 7) •
12.6

State 6 Routine - Yfl6 (LOADING XXXXXX)
The purpose of this routine is simply to eliminate the Summary

display replacing it with the message "LOADING XXXXXX"

(where XXXXXX

is replaced by the name of the DUP being loaded) and set to Y~S to
a JMP Yfi!SA.
12.7

State 4 is then entered via the State Changer.

State 7 Routine
The State 7 routine is a rather special case.

When a

transition to state 7 occurs, State 5 is entered at Y[ISB with
interrupts off.

At Y/ISB, the variable STATE is set to 5, and the DEMO

INDEX is then read into segment fl, quarter 3.
7 with interrupt

STATE is then set to

off, TAPMES is set to the standard message "TAPE

. OPERATION IN PROGRESS" and ADML is cleared because the program will
not be a clean copy once the DUP is started.
Finally, Yfl7, in segment fl is invoked, which starts the DUP
at the saved state or at a fresh state.

The fresh state is defined

as:

overflow
tape extended operation register
extended function register
MQ

clear

fl¢¢¢
14flfl
fd¢¢fl

IF:: 2, DF = 3
20

fields
PC

mode

LINC

link

fd
fdflflfl

12 - 3

12.8

State 8, 9, and 1{6 Routine - Yl¢ (DEMO Help)
This state is the DEMO Help State.

When entered it is

initialized so that the first and last frames are known, then
the first frame is read from tape and displayed.

The characters

F, B, Control F, and Control B cause the routine to advance or back
up one frame

(but not beyond the ends} and to read the new frame

from tape if that is necessary, then to display the new frame.
12.9

State Changer

(11, 12, 13, 14)

The State Changer is entered at SCI from the interrupt
handler in segment ¢.
STATE.

The new state has already been stored in

The routine simply uses the value of STATE to jump to the

appropriate routine through a table.
If a new state is 7, interrupts are not turned on by the
State Changer.
The routines for states 11, 12, 13, and 14 are included within
the state Cllanger since they are very short.
12.9.1

(See paragraph 7.1)

NXSTAT

NXSTAT is an auxiliary entry to the State Changer.
always called from segment l.

It is

The new state is in the word following

the JMP NXSTAT.
12.10

Directory Lookup Routine
There are actually two directory lookup routines.

DLOOK

looks up the full 8 character name in ZPNAME, attempting to find
a match in the DEMO D'ldex.

DLOOF only matches the first two

characters of ZPNAME for group lookup.

If successful, the directory

pointer is left in register 1¢ and the AC.

12 - 4

Display Subroutine

12.11
1~e

display routine is based on QANDA, but is nevertheless

guite different.
12.11.1

There are two display modes.

Normal Display Mode (QANDA compatible)

In the normal mode, the call to DSPLAY is as follows:
JMP
TEXT

DSPLAY

ADDRESS
X/Y Coordinates
(all returns)

12.11.l.l Text F,ormat
The following special characters are recognized in the text:
34 8

43 8

- Carriage return

Ter~ination

character

f36a

(F)

- When the f:Lrst character of a line only,
caus,es the line to be displayed full-size.

llifa

(H)

- When the first character of a line only,H generates
- half-size characters ifor QANDA compatibility).

12.11.1 .. 2 X/Y Coordinates
The X and Y coordinates are generated by multiplying each
halfword parameter by llifa·

If both X and Y are zero, the parameter

is ignored: display will continue at the beginning of the last line
of the previous display.
12.11.2

Special Mode for 1 Index Display

If the first character of the text is a jifjif8 ,
entered.

In this mode, the call

a special mode is

and the interpretation of X/Y

are the same as in normal mode, but the text is specially interpreted as follows.

12 - 5

12.ll.2

special Mode for Index Display (continued)
Terminator
Carriage return
Causes half size to take effect
Causes full size to take effect

12.12

DCALL is used only during initialization to call the display
subroutine from segment 2.

It is overlayed at runtime by the 6

character DUP name and the pertinent directory information for
that DUP.
12.13

TAPDSP
TAPDSP is the routine which runs while trapped tape operations

are being processed.

It calls the display subroutine, which

returns to the AC the number of characters that were displayed.
Tri.is is added to a counter, TIMER, in segment ~.

If the counter

goes positive, the tape has taken too long to process the last
command and is assumed to be either in the end zone or otherwise
lost.
The remainder of segment 1 is filled with messages, as described in section 13.

12 - 6

13.0

MONITOR Messages

13.1

Messages During Operation of the DEMO Monitor
The following error messages may occur during the operation of

the DEMO Monitor.
13.1.l

"SPURIOUS INTERRUPT"

An interrupt has occurred which could not be identified by
the DEMO Monitor and either there was no interrupt extension
routine, or the interrupt extension routine returned to the location tagged "MARK" rather than "MARK"+ 1 indicating that it could
not identify the interrupt.
The interrupt has been cleared by the DEMO Monitor through
use of a Power Clear, and processing will continue if a Control C
is typed.
13.1.2

"lTNCLEARABLE INTERRUPT"

An unidentifiable interrupt has occurred as in 13.1, but
Power Clear was unable to clear the interrupt.
In order to proceed, it will be necessary to find the cause
of

the undesired interrupt and clear it.

13 .. 1.3

CANNOT FIND
PRCGRAM OR GROUP
XXXXXX''

xxxxxx is the six character name entered from the keyboard
during the last DEMO INDEX display.
in the DEMO INDEX.

No program by that name exists

If the name is a single letter, this message

also indicates that no group exists by that name.

13 - l

13.l.4

UNIT n
ILLEGAL WRITE .
BLOCK mmm"

During the execution of a DUP, a Tape Write, Write-Check, or
Write-Check-Group instruction has occurred which would write on unit
non block nunm which is outside the range 103-152.

It is necessary

to restart the current DUP and assure that the program will not
attempt to write outside of the assigned area.

Restart with

Control s or retry the instruction with Control c.
13.1.5

"UNIT n
NOT SELECTED"

An attempt has been made to operate on a tape unit which is
not currently in the system.

The following problems may have

occured:
l.

No tape unit has its thumbwheel selector turned to
the appropriate unit number.

The unit which has its thumbwheel turned appropriately
is not in "Remote.
11

After correcting the problem, typing Control C will effect
an attempt to re-execute the same instruction again.
13.1. 6

UNIT n
BAD BLOCK mmrn 11

The tape control unit is having difficulty moving toward
some tape block.

The difficulty is occurring near block mmm.

Typing Control c will cause the command to be retried.

13 - 2

13.1.7

"UNIT n
BAD TAPE"

This error message occurs when a tape operation takes unduly
long {about four seconds) to complete.

Generally, one of the

following errors has occurred:
1.

A Read-Check or Write-Check instruction cannot be

completed because of a checksum
2.

error.

The tape is in either end-zone and cannot find its way out.

If the latter occurs, the tape can be manually moved out of
the end-zone.

Typing Control C will cause the command to be

re-executed. If you are in end zone, you must manually wind tape.
13.1.8

"U~UT n
SI::T WRITE

ENABLE•

A write instruction to unit n cannot be completed because the
tape is protected.

Typing Control C will cause the command to be

re-executed. Make sure to set the write enable swit.ch.
13.2

Messages occurring Anytime
The following messages may appear at any time:

13.2.1

"TAPE OPERATION IN PROGRESS"

This message is displayed whenever tape is being moved and
there is no more appropriate message to be displayed.

During DUP

execution, this message is always displayed during tape instruction
processing.
13.2.2

xxxxxx

DEMO USER Program XXXXXX is being loaded and will be started
as soon as the load is complete.

a.3 - 3

14.0

Programming Conventions for DEMO U.ser Programs
DEMO User Programs which are to run under the PDP-12 DEMO

Monitor are relatively easily implanted in the total DEMO System.
Due to certain hardware restrictions it is not possible to check
for certain program operations which might interfere with the
proper operation of the DEMO Monitor.

Accordingly, the following

programming restrictions must be placed on DEMO User Programs.
DEMO user Program Instruction Restrictions

14.1

TTY interrupt, ION (General Interrupt), Instruction Trap,

and Tape Trap should not be turned of~ except as noted in 14.7.1,
below.
The DEMO Monitor runs with these PDP-12 features enabled to
permit it to check for LINCtape
control of the TTY keyboard.

errors and provide overriding

Disabling of any of the above

features will prevent error checking and TTY control and thus
should be avoided, although it cannot be prevented.
14.2

Special Functions Register

SF bits 4 Character Size, and 5,Fast Sample,are the only bits
in the SF which may be modified by a DEMO Program: otherwise, you
run at your own xisk.
14. 3

DEMO user Program (DUPL Core use (up to 6K Decimal!)
DUP's are restricted to LINC Memory Segments 2, 3, 4, 5, 6, and

7 (PDP-8 loc.

4¢¢¢-17777)~

PDP-8 page zero references 0-177 are

not allowed.
14. 4

DUP Star.t Conditions
DUPs

must start in LINC mode at Loe~

in segment 2 although

they may contain either PDP-8, LINC, or mixed mode.

14 - l

DUP use of LINCtape

14:.5

LINCtape blocks

0-2~

unit

(SCRATCH.)
~

and 16-17 unit 1 are reserved for

use by the DEMO Monitor, since DEMO Monitor tapes also contain DIAL,
the LINCtape blocks used by DIAL are also reserved.
are reserved for a scratch area

Blocks 103-152

(SCRATCH.) and is the only legal

area DEMO Monitor recognizes as writeable by DEMO User Programs.
14.6

DUP Write Protection
LINCtape blocks 103-152 on any unit should be .available for

writing.

Reading is permitted anywhere on any unit.

SCRATCH

blocks 103-152 is a DIAL file which reserves those blocks on
DEMO Monitor tapes. Attempts to write on any other blocks of
tape are stopped by the DEMO Monitor.
illegal instruction: Control
14.7

Control C retries the

s reloads the DUP.

Tape Extended Operations Register
TEOR bits

and 11 (extended unit bits) are the only TEOR

bits which may be altered by a DUP.
14.7.1

NO PAUSE Tape operations
Tape operation may only be performed in NO PAU.SE mode by

disabling tc:t.pe traps before executing the tape instru.ction.
Operations performed in this manner have full use of the Tape
Extended Operations Register.
It should be noted that tape operations performed with tape
trap turned off are not checked at all by the DEMO Monitor.
14. 8

Operate Instruction, OPR us.age

(also see paragraph 11. 2)

Several OPR instructions are provided for use by DUPs.

The

following paragraph specifies these instructions and their use.
14.8.1

RETV (OPRS)
RETV may be used to retrieve tape location information about

any file in the DEMO Index.

It is called as follows:

14 - 2

14.8.1

RETV (OPRS)

(continued)

RETV

/OPRS

ADDR

/Address of parameter region

ADDR must be a LINC-mode address.

The parameter region

must be in the current Instruction Field.
ADDR,

TEXT
5606
1114
0516
0115

•

Its format is:

FILENAM"

.FILENAM must be the full 8 character name as it appears in

the DIAL Index and if not 8 characters, fill with 779.
RETV returns the following information in ADDR+ 4, 5, 6, and 7:
ADDR 1"" 4
ADDR + 5
ADDR + 6
ADDR +- 7

Source_block number
Source length
Binary block number
Binary length

If no entry is found in the DEMO INDEX for .FILENAM, ADDR+- 4,

5, 6, and 7 will not be altered.
14.8.2

NEXT (OPR6)

NEXT is a variation of EXIT (14.8.3) which causes the next
DUP which is a member of the same group to be loaded in preparation
for execution.

It is logically equivalent to typing Control N

during DUP execution.
If there are no further DUPS

in the group, Display Index

will be entered.

14.8.3

EXIT

(OPR7)

EXIT is provided to be used in the place of either PDP-8
mode or LINC-mode HLT instructions, although it must be executed in
LINC-mode. It will redisplay the DEMO Index.
14 - 3

XCHN ... (OPRll)

14.8.4

XCHN extends the interrupt service chain to allow processing
of interrupts from devices other than the console Teletype or
LINCtape.

Its use is as follows:
XCHN

/OPRll

PM ODE

RNAME
!MODE

/Routine name in full PDP-8 mode
Address

The following restrictions apply to the routine RNA.ME:
Interrupts must not be enabled.
The routine must start and finish in PDP-8 mode although
LINC-mode may b>e used within the routine.
The routin·e should be in the followin~ format:
RNAME, $J

/Entry point
/Test devices and
/set or clear
I internal flags

JMP I RNAME

ISZ
RNAME
JMP I RNAME
14.8.5

/Return - no flags found
/Return to .+l if the
/source of the interrupt
/was identified.

QKST (Oprui>

OKST is provided to perform the same function as KST.
Because the DEMO Monitor operates with interrupts on, the keyboard
flag will never be apparent to the DUP.

OKST tests an internal

keyboard flag and fu·11ctio~1s just like KST. Note that OKST can
not be used indirectly, although KST can (KST I).

14 - 4

14.8.6

KBIIA \OPR13)

KBDA returns the :foll ASCII keyboard character last received
in the AC.

The character is echoed, and lin.e ',:eeds are provided
/

for carriage returns.

If no character has been rece~ved since

the last KBD or I<BDA, then one of the following occurs:
If the I bit is on in the KBDA instruction, the DEMO Monitor

waits for a character from the keyboard before returning.
If the I bit is not on, the instruction returns with a clear

AC.
14.8.7

TYP (OPR14)

TYP causes the full ASCII character in the AC to be typed
on the console TTY.
14.8.8

KBD (OPR15)

KBD functions similarly to KBDA, except that the LINC-code is
returned in the AC rather than the full ASCII code.

If the code

returned is a CASE (23 8 ), the next KBD will return the LINC-code.
If no character has been received since the last KBDA, the
instruction behaves the same as KBDA (see paragraph 14.8.6).

!4.9

DUP Instruction Restrictions
The DUP should not halt or do anything which leaves the

system in limbo (i.e., IOF1 JMP

.).

These situations cannot

be trapped or detected by the DEMO Monitor.

14 - 5

15.(J

DUP TEXT Files (Surrunary and Help Frames)
DUP Help and Summary Frame files are prepared using the

TEXT pseudo-op in DIAL.

It should be noted that the DEMO Monitor

expects to find an assembled binary file without a header block
located in the blocks indicated in the DEMO INDEX as the source
blocks of a DUP.

we do not use the source blocks as actual source,

but rather binary DUP TEXT files containing the Summary and Help
Text for that DUP.

They follow the standard PDP-12 QANDA conven-

tions, plus the followng rules:
l.
QANDA

DUP display frames cannot exceed 256 characters (including

control characters).
2.

DUP display files must contain the Summary Frame as the

first frame of the file.
3.

DUP display files must contain an odd nUmber of DEMO Help

Frames (Summary Frame plus odd number of Help Frames
tape blocks, as illustrated in figure
4o

even number of

15-2.;·

DUP display frames must be align·ed on 2fdf18 word bound-

aries beginning at *fd.
D~l'P

15. l

s,ununa.ry and Help Frame Assembly and
Storage Procedure

Assemble as usual.

store as some scratch binary file,

Create a fake source file for the DUP for which the

(i.e., SS DOO, N).

current text is being prepared which is one block less than the
number of blocks in the saved binary of that text.
4.

Using the PI procedure, transfer the saved binary text

(with the header block ignored) to the fake source file just
created.

15·"1

Number of Help Frames (must always pe odd)
Number of LINCtape blocks required to keep
Summary and Help frames for a particular DUP.

LINC TAPE

rfB= N+l

SOURCE

*O
ummary
Frame
200

(128)

1st Help.
Frame

·256 characters

max./128 w0rd (
Summary or Help
Frame
' · 11 ~,:
":
1 Ir ..

400

2nd Help
Frame

3rd
Help
Frame

600 •

Llt

LINC tape
blocks

*Successive
128

word
Bd\.mdaries
define the

Start of
each
Help
Frame to
N frames
.tape
(N*200)

block

Last Help
Frame

15 - 2

16.0

Creating a DEMO Monitor Tape
The following procedure may be used to create a DEMO Monitor tape

after any changes or modifications have been made to any Monitor Code.
16.1

Cross Segment References
Each

subsystem of the DEMO Monitor (except LOADER) has a

section of references to other subsystems.

In the even.t that a

modification is made which moves any of the referenced locations,
the reference assignments in other subsystems
16.2

must

be revised.

Assembly
Each subsystem is self-contained and may be assembled as an

entity in the conventional manner using DIAL, saving binaries
of each subsystem.
16.3

The DEMO Monitor binaries
The binaries should be copied as noted· below to create a

self-loading DEMO Monitor.

See figure page l.6-2o

Note that the first block of the saved binary is a header block,
so the first program block is :the one ~ the header block
from the DIAL Directory.

The last block iQ the binary of SEG¢

and S.EGl is empty and automatically generated by DIAL Assembly.
See section 4.4 of the LAP.6-DIAL Manual., DEC-12-SEZB-D.
16.3.1

":P!P1hg" the J2ieces to9ether

FILE
SEG~

SEG[i§
SEG¢
SEG¢
SEGl
SEGl
SEGl
SEGl
INITLIZE
INITLIZE
LOADER

RELATIVE FILE:
Block 2
Block 3
Block 4
Block 5
Block 2
Block 3
Block 4
Block 5
Block 2
Block 3
Block 2

Copy to DEMO Monitor Tape Block l
Copy to DEMO Monitor Tape Block 2
Copy to .DEMO Monitor Tape Block 3
Copy to DEMO Monitor Tape Block 17
Copy to .DEMO Mdnitor Tape Block 4
Copy to .bEMo Monitor Tape Block 5
Copy to DEMO Monitor Tape Block 6
Copy to DEMO Monitor Tape Block 7
Copy to DEMO Monitor Tape Block 1¢
Copy to DEMO Monitor Tape Block 11
Copy to DEMO Monitor Tape Block ¢

16 - 1

16.4

Talk BALLOON
There is no symbolic for the Talk BALLOON.

The binary for

the talk balloon is BALLOON.
FILE:
. RELATIV>E F:tLE:
Block 2
Blbck 3
Block 4
Block 5

BALLOON
BALLOON
BALLOON
BALLOON

522

MARK12

511

PIP
EX.PROG•

470
524

AD DEMO

526

21
2
3
3
3

BINLOAO
LBS IM
CONVERT
F'OCAL8K
F'OCAL4K
CAROLS
LOADER
INITLIZE
SEG0
SEGl
BALLOON
04-01-70

Block 12
Block 13
Block 14
Block 15

DE?1_0 INDEX Cte1n•1tu

16.5
DIAL-V2

Copy to DEMO Monitor Tape
Copy to DEMO Monitor Tape
copy to DEMO Monitor Tape
Copy to.DEMO Monitor Tape

520
614
535
540

2
17

635
641
663

725

527

543
550
573
617
637
660
717
763
771

PI
A

SOURCE

23 JL0J6'10,
21
L0J 0
11

NAME

~LOADER.

J~c

6~01661.2
L0J10
c

c01123,,1
l0J17

INITLIZ.

10
11
12
17

SEG04-4.
DMOINDX.
Q AND A.

·DA-DTST
• DDATAl 2
·DMAGSPY
·DF'RQANA
.OD I AL
·EF'REQ12
• EWAVES
·EB.BALL

·EBASMEM
0J.764.9 4
L0J4

-;>L0J 772 .. 4
L0Jl2

LOAD DEMO

• F'SOLACE

·F'MUSIC
eF"KALEID
·F'DRAW
·F'ECHASK
• F'SPCWAR
eTDAYCOM

24
26
32
35
45
46
50
52
53
54
55
56
57
61
63

1
2

22
165
37
153
72
163

2
3
6
10

170

3
3

173
176
201
206
210
216
220
223
226

2
4

2
2
l
2

2
1

1
l
l

1
2
2
1

24-4

• TSTPWCH

66
67

• TCLOCK
SCRATCH.

71
103

250
256

263

INOEXSRC

4
1
1
5

GREETING

16 - 2

BLKS
1
1
3

~EGt J-4.

ALLOON.

BINARY
BN

GREETIN.

81.120,,3
L0JI
A

BLKS

SEG01-3.

776

2
3

2
6
2
3
3

16
4
6

(see Pl()W Chart next pa,qe)

17.0

9.J~ratins

17.1

Lcadins - Twp ta:ees (DEM012 tapes only)

Procedures

Mount both tapes on units and set the units to ¢ and 1. Be-

cause the tapes are identical, either tape can be on either unit.
J

Write Enable both tapes.

Place ¢7¢¢ in the ~eft Switches and ¢¢¢¢ in the Right

switches.

stop the computer if it is running.

Press I/O PRESET

Press DO and wait for tape to stop moving

Press START 2/1

The system will load and begin execution.

No further

operations are required except as requested on the display scope.,

17.2

Loading - One Ta:ee
In the event that a special tape is to be used with a DUP it

will be required that the Index and Display Index be written on
tape ¢ instead of .1.

The startup procedure is then the same as

for two tapes, but the DEMO Monitor ta.pe must be on unit ¢
Enabled}, and tape 1 must not be Write Enabled.

(Write

In order for DEMO

Monitor to recognize unit 1 for its Index, use initialization must
take place again.

Likewise, if.initialization starts with unit 1 on,

the Monitor assumes it should be on during all your DEMO use. The-only
way to get DEMO to stop looking at unit l is to go through initialization again.

17.3

Restarting
If it is necessary to restart the DEMO Monitor, the starting

procedure (including initialization) must be reexecuted.

The loading

procedure in 17 .1 or 17 .2 should be foll.owed or else use of the DIAL
File AD DEMO will ·start the DEMO Monitor without having to toggle
the console switches.
17 - 1

Q§...Molft US.E FLOW CHART
;;:,

MOUNT DEM012 TAPE ON
IGNORE UNIT
IF Y
ti~UT ~ SET WRITE ENABLR'l-·~lwANT BY PUTTING IT
R~arE ON BOTH UNITS
IN LOCAL, OTHERWISE
AND ~HND TA S
OUNT ANOTHER DEM012

SET ALL 1---~!1£!..,.J~::!.tA(t
ONSOLE
SW I TC HE
0

ON UNIT
SET LOCAL
WIND MORE LEADER BY
PRESSING LEFT ROCKER
SWITCH AND SET
DEM012 INITIALIZES
BY SCANNING THE
DIAL DUPLICATE
DIFECTORY IN BLOCK
20 AND CREATES ITS
OWN INDEX IN
ALL THE WHILE
DISPLAYING
INITIALIZATION
IN PROGRESS

ERROR MESSAGE ·
UNIT ¢ NOT
SELECTED

TRY AGAIN

SET REMOTE LOCAL
TO REMOTE ON
..__ _
1
UNI'1

ERROR MESSAGE S T
WRITE ENABLE ON
UNIT ¢ AND/OR
UNIT l, TYPE G

VR12 DISPLAYS
INDEX
GROUP D-----GROUP E-----THE DEMO INDEX
TYPE IN PROGRAM
IS NOW DISPLAYED
IT CTRL I,T
~O~R~G~R~O~ULJP~-~-~-~-~-:..........~~~~--tWITH ALL PROGRAMS..-.---~ONLY LEGAL CCMMAND
YOU MAY CALL BY
THAT DOES ANYTHING
IF YOU SPELL THE
TYPING ONE OF THE
~H~E~R~E~~--~~~----GROUP LETTERS OR
PROG NAME IVRONG
FULL NAME OF ANY
EM012 TELLS YOU.
IF YOU HAVE A BAD
PROGRAM DISPLAYED
IS STILL LOADING
PELLING,RUBOUT
CALLED,THE DISPLAY
Y ERASES A
HARACTER AT A
IME

SUMMARY FRAME
REPLACES INDEX
DISPLAY WHEN
EM012 FINDS
HE BI.I< # 1 S
OF SOURCE AND
BINARY OF THE
PROGRAM. SUMMAR
FRAME REMAINS
ON VR12 UNTIL
TRL S, I, ARE
STRUCK.

THE LOADING DISPLAY
GOES AWAY AND THE
PROGRAM EXECUTES
WI'rH ·MONITOR
""I-~--~----~WATCHING FOR CTRL
KEYS OR ANY ODD USER
OPERATIONS SUCH AS
TRYING TO WRITE ON
TAPE ILLEGALLY, OR
SHUTTING POWER OFF,
DISPLAY lST HELP FRAME TYPE
ETC.
TO MOVE BACKWARD OR FORWARD
FRAMES.

17.4

Terminating
No special procedure is required for terminating the DEMO

Monitor.
17.5

Error Conditions
All runtime errors are handled similarly.

In all cases, a

reasonable ·state will be entered if a Control £ is struck except
in the case where an unclearable interrupt occurs.

In that case, a

restart is required after the unclearable interrupt is removed.
If the initialization routines have any difficulty reading
in the Block 20 Index, the message "BAD TAPE - RESTART DEMO" may
appear.

occasionally, a simple restart from step 2 of 17.1 will

get past the error.

If that fails, tape units ¢ and 1 should be

swapped and an attempt should be made to run from the other taf>e.

17 - 2

DIAL Character Set

Kexboard
A
B

c
D

E
F
G
H

I
J

K
L
M
N
0
p
Q

v
w

z
[

\
]
t

(SHIFT/K)
(SHIFT/L)
(SHIFT/M)

SPACE

#
$
%
&

(
)

External
(ASCII)
301
302
303
304
305
306
307
310
311
312
313
314
315
316
317
320
321
322
232
324
325
326
327
330
331
332
333
334
335
336
337
240
241
242
243
244
245
246
247
25v
251
252

Internal
1
2
3
4
5
6
7
10
11
12
13
14
15
16
17
20
21
22
23
24
25
26
27
30
31
32
33
34
35
36
Illegal (not displayed)
40
41
42
Illegal (not displayed)
44
45
46
Illegal (not displayed)
50
51
52

Character Set (Cont)
Ke:z:board

I
$§

1
2

3
. 4i
5
6

7
8
9

External
(ASCII)
253
254
255
256
257
260
261
262
263
264
265
266
267
270
271
272

<
>
?
@

LINE FEED
RETURN

ALT MODE
RUBOUT
CONTROL/I (TAB).

273
274
27'5
27'6
277
300
212
215
375
377
211

Internal
53
54

55
56
57
60
61
62
63
64
65
66
67
70
71
72·

73
74
75
76
77

Illegal (not displayed)
37
(not displayed)
43
II
None II
II
None "
47
"
"

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<)uestions or problems concemrng DEC Software should be reported to the Software Specialist at your nearest DEC
regional or district sales office. In cases where no Software Specialist is available, please send a Software Trouble
Report form with details of the problem to:
Software Information Service
Digital Equipment Corporation
146 Main Street, Bldg. 3-5
Maynard, ~assachusetts 01754
These forms. which are available without charge from the Program Library, should be fully filled out and accomparned by teletypt:' output as well as listings or tapes of the user program to facilitate a complete investigation. An
Jnswer will be st:'nt to the individual and appropriate topics of general interest will be printed in the newsletter.
\l'\\ and re\ised software and manuals, Software Trouble Report forms, and cumulative Software Manual Updates
Jrl· available from the Program Library. When ordering, include the document number and a brief description of
thl' program or manual requested. Revisions of programs and documents will be announced in the newsletters and
a price list will be included twice yearly. Direct all inquiries and requests to:
Program Library
Digital Equipment Corporation
146 Main Street, Bldg. 3-5
Maynard, Massachusetts 01754
D1git:1I f-qu1rme11t Computer Users Society (DECUS) maintains a user Library and publishes a catalog of programs
as well as the Df-CUSCOPE magazine for its members and non-members who request it. For further information
plea~e wntt· to:

DEC US
Digital Equipment Corporation
146 Main Street
Maynard, Massachusetts 01754

Stnd Digital's software newsletters to:
Name~----~------------Company Name _ _ _ _ _ _ _ _ _ _ _ _ _ __
Address-----------------~

(zip code)
PDP-8/I 0
PDP-8/L 0
LINC-8 0
PDP-12 0
PDP-9 0
PDP- I 5 0
Please specify
OTHER 0 _ _ _ _ __
PDP-JO 0
\1y system serial number is _ _ _ _._ _ _ _ _ _ _ (if known)

\1) computer is a

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FIRST CLASS
PERMIT NO. 33
MAYNARD, MASS.

AL'">l'-FSS REPLY MAIL
SO POSTAGE STAMP NECESSARY IF MAILF.D IN THf UNITED STATl-'S

Po~t;ige v.111 he paid by:

mnmnama
Digital Equipment Corporation
Software Information Services
146 Main Street, Bldg. 3-5
Maynard, Ma~chusetts 01754

READER'S COMMENTS

DEM012 TECHNICAL
REFERENCE MANUAL
DEC-12.MRZA- D

D1!!it<1I Equipment Corporation maintains a continuous ef(ort to improve the quality and usefulness, of its
puhlic<itions. To do this effectively we need user feedback - your critical evaluation of this manual.
Pk<isc comment on this manual's completeness, accuracy, organization, usability, and readability.

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Dl:.C al~o strives 10 keep its customers informed of current DEC software and publications. Thus, the following period1cJll} d1\lr1buted publ1cat1ons are available upon request. Please check the appropriate boxes for a current issue of the
publu.:at1on(si desired.

Sofrware Manual Update, a quarterly collection of revisions to current software manuals.

l 1scr\ Bookshelf. a bibliography of current software manuals.

Program Library Price List. a list of currently available software programs and manuals.

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C11y _ _ _ _ _ _ _ _ _ _ _ S t a t e - - - - - - - - - - - - - - - Zip or Country-----

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Fold Here - - - - - - - - - - - - - - - - - - - -

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FIRST CLASS
PERMIT NO. 33
MAYNARD, MASS.
AL'~l'-FSS Rf PLY MAIL
'-0 POSTAGE STAMP NECESSARY IF MAILED IN THE UNITED STATl-'S

Pmt;ige 1oA. ill he paid by:

mnmaama
Digital Equipment Corporation
Software Information Services
146 Main Street. Bldg. 3~5
Maynard. Massachusetts 01754