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digit.al equipment. corporation

DEC-9A-MRZA-D

PDP-9
BACKGROUND / FOREGROUND MONITOR SYSTEM
PROGRAMMER1S REFERENCE MANUAL

To OBTAIN ADDITIONAL COPIES OF THIS MANUAL, ORDER
NUMBER DEC-9A-MRZA-D FROM THE PROGRAM LIBRARY,
DIGITA.L EQUIPMENT CORPOR:ATION, MAYNARD, MASSACHUSETTS,
$4.50
01754
PRICE

CONTENTS

SEC'rION 1

BACKGROUND/FOREGROUND MONITOR

1.1

INTRODUCTION

1-1

1.2
1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
1.2.6

BACKGROUND/FOREGROUND MONITOR FUNCTIONS
Scheduling of processing Time
Protection of FOREGROUND Core and I/O
Sharing of Multi-Unit Device Handlers
Use of Software Priority Levels
Use of Real-Time Clock
Communication Between BACKGROUND and
FOREGROUND Jobs

1-1

1-3
1-5
1-5
1-7
1-7

EARDWARE REQUIREMENTS AND OPTIONS

1-8

1.3

SECTION 2

1-7

BFKM9 - NON-RESIDENT BACKGROUND/FOREGROUND MONITOR

2.1

INTRODUCTION

2-1

2.2

LOCATION AND WHEN CALLED

2-1

2.3

INITIAL OPERATION

2-2

2.4
2.4.1
2.4.2
2.4.3
2.4.4

INFORMATION COMMANDS
The LOG Command (L)
The REQUEST Command (R)
The DIRECT Command (D)
The INUSE Command (I)

2-5
2-5
2-6
2-7
2-7

2.5
2.5.1
2.5.2
2.5.3
2.5.4
2.5.5
2.5.6
2.5.7
2.5.8
2.5.9
2.5.10
2.5.11
2.5.12
2.5.13

ALLOCATION COMMANDS
The ASSIGN Command (A)
The FILES Command (F)
The FCORE Command
The FCONTROL Command
The BCONTROL Command
The NEWDIR Command (N)
The SHARE Command (S)
The NOSHARE Command
The 7CHAN Command (7)
The 9CHAN Command (9)
The VC38 Command (V)
The MPOFF Command
The MPON Command (M)

2-8
2-8
2-10
2-12
2-13
2-14
2-15
2-16
2-17
2-17
2-17
2-18
2-19
2-19

2.6

PROGRAM LOAD COMMANDS

2-20

2.7

FINAL OPERATION

2-20

2.8

CONTROL CHARACTERS

2-20

2.9

SUMMARY OF COMMANDS

2-21

CONTENTS (Cont.)

SECTION 3

CONTROL CHARACTERS

3.1

PURPOSE

3-1

3.2

CONTROL TELETYPE

3-1

3.3

TELETYPE HANDLER

3-2

3.4

CTRL C (tC)

3-2

3.5

CTRL S (tS)

3-3

3.6

CTRL T (tT)

3-3

3.7
3.7.1
3.7.2
3.7.3

CTRL P (tP)
NORMAL CTRL P
No Change
REAL-TIME CTRL P

3-4

3.8

CTRL R (tR)

3-7

3.9

CTRL Q (tQ)

3-8

3.10

CTRL U (@)

3-9

3.11

RUBOUT

3-10

3.12

CTRL D (tD)

3-10

SECTION 4

3-5
3-6
3-6

LOADERS

4.1

INTRODUCTION

4-1

4.2
4.2.1
4.2.2
4.2.3

FOREGROUND LINKING LOADER
Option Characters and Their Meanings
Use of +
Terminator
Sequence of Operation

4-1
4-2
4-2
4-3

4.3

BACKGROUND SYSTEM LOADER

4-4

4.4

BACKGROUND LINKING LOADER

4-6

4.5
4.5.1
4.5.2

LOADING XCT FILES
EXECUTE in the Foreground
EXECUTE in the Background

4-7
4-8
4-9

4.6

ERROR CONDITIONS

4-9

4.7

SYSTEM MEMORY MAPS

4-11

CONTENTS (Cant.)

SECTION 5

BACKGROUND/FOREGROUND START-UP PROCEDURE

5.1

LOADING THE B/F MONITOR

5-1

5.2

.IDLE LOADED AS THE FOREGROUND JOB

5-2

5.3

SINGLE-USER FOCAL LOADED INTO THE FOREGROUND

5-3

5.4

TWO-USER FOCAL LOADED' IN THE FOREGROUND

5-3

SECTION 6

BACKGROUND/FOREGROUND MONITOR COMMANDS

(SYSTEM MACROS)

6.1

INTRODUCTION

6-1

6.2

.REALR

6-2

6.3

.REALW

6-3

6.4

.IDLE

6-4

6.S

.IDLEC

6-1';

6.6

.TIMER

6-5

6.7

.RLXIT

6-6

6.8

MAINSTREAM REAL-TIME SUBROUTINES

6-7

SECTION 7

WRITING DEVICE HANDLERS FOR THE BACKGROUND/FOREGROUND
MONITOR SYSTEM

7.1

INTRODUCTION

7-1

7.2
7.2.1
7.2.2
7.2.3

FORMAT OF DEVICE HANDLER'S CAL PROCESSOR
SETUP
Initiating I/O
.OPER Functions

7-2
7-8
7-8
7-9

7.3

FORMAT OF DEVICE HANDLER'S INTERRUPT PROCESSOR

7-9

7.4
7.4.1

SYSTEM ANNOUNCEMENTS
Errors

7-13
7-13

7 ..5

STOP I/O TECHNIQUE

7-17

7.0
7.6.1

SEQUENTIAL MULTI-USER DEVICE HANDLER
.WAITR

7-19
7-20

7.7

DEVICE HANDLER LISTING

7-20

CONTENTS (Cont.)

SECTION 8

SYSTEM GENERATION

8-1

APPENDIX I

.SCOM REGISTERS

r"-1

APPENDIX II

ERRORS

II-1

APPENDIX III

TELETYPE HARDWARE CHARACTERISTICS

1II-1

SECTION 1
BACKGROUND/FOREGROUND MONITOR

1.1

INTRODUCTION
The reader is assumed to

bE~

familiar with the Keyboard Monitor

environment as described in the Advanced Software Monitors Manual,
DEC-9A-MADO-D.

It should also be noted that all material presented

herein supersedes the information given in the Monitor Manual.

1.2

BACKGROUND/FOREGROUND MONn~OR FUNCTIONS
The Background/Foreground Monitor is designed to control proces-

sing and I/O operations in a real-time or time-shared environment.
It is, essentially, an extension of the Keyboard Monitor and al10ws
for time-shared use of a PDP-9 by a protected, priority, user F'!REGROUND program and an unprotected system or user BACKGROUND program.
The Background/Foreground Monitor greatly expands the capabilities of PDP-9 ADVANCED Software and makes optimum use of all available hardware.

It permits recovery of the free time (or dead time)

that occurs between input/output operations, thus promoting 100%
utilization of central processor time.
FOREGROUND programs are defined as the higher-priority, debugged
user programs that interface with the reaL-time environment.

They

normally operate under Program Interrupt (PI) or Automatic Priority
Interrupt (API) control, and are memory protected.

At load time

they have top priority in select.ion of core memory and I/O devices,
and

execution time they have priority (according to the assigned

priority leveLs) over processing time.

1-1

Depending upon system require-

ments, the user's FOREGROUND program could be an Executive capable
of handling many real--time programs or subprograms at four levels
of priority (with API present).
BACKGROUND processing is essentially the same as the processing normally accomplished under control of the Keyboard Monitor.
That is, it could be an assembly, compilation, debugging run, production run, editing task, etc. BACKGROUND programs may use any
facilities

(for example, core, I/O and processing time) that are

available and not simultaneously required by the FOREGROUND job.
Under certain circumstances, I/O devices may be shared by both
the FOREGROUND and the BACKGROUND jobs.
The Background/Foreground Monitor system is externally a
keyboard-oriented system; that is, FOREGROUND and BACKGROUND
requests for systems information, core, I/O devices, programs to
be run, etc., are made via the Teletype keyboards.

At run time,

the Monitor internally controls scheduling and processing of I/O
requests, while protecting the two resident users.
The Background/Foreground Monitor performs the following
functions as it controls the time-shared use of the PDP-9 central
processor by two co-resident programs:
a.

Schedules processing time.

Protects the FOREGROUND job's core and I/O devices.

Provides for the sharing of multi-unit device handlers,
such as DECtape, by both FOREGROUND and BACKGROUND jobs.

Allows convenient use of API software levels by
FOREGROUND jobs.

1-2

Provides for convenient and shared use of the
system Real Time Clock.

Allows communication

b(~tween

the BACKGROUND and

FOREGROUND jobs via core-to-core transfers or
by the shared use of bulk storage devices.
1.2.1

Scheduling of Processing Time

At run time, the FOREGROUND job retains control except when it
is I/O bound; that is, when completion of an I/O request must
occur before it can proceed any further.

In the following

example, if the .WAIT is reached before the input requested
l)y

the . READ has becn completed, control is ·transferred to ,\

lowc'r priori ty FOlmGROUND segment or to the BACKGROUND job

until the input for the FOREGROUND job is completed.
.READ 3, 0, LNBUF, 48

/READ TO .DAT SLOT 3

.WAIT 3

/WAIT ON .DAT SLOT 3

Since multi-unit device handlers can be shared by FOREGROUND
and BACKGROUND programs, there is a mechanism by which a FOREGROUND I/O request will cause a BACKGROUND I/O operation to be
stopped immediately so that the FOREGROUND operation can be
honored.
is

On completion of the FOREGROUND I/O, the BACKGROUND I/O

resumed with no adverse effects on the BACKGROUND job.
The FOREGROUND program can also indicate that it is I/O

bound by means of the .IDLE or .IDLEC command (Section 6.3 - 6.4).

1-3

This is useful when the FOREGROUND job is waiting for real-time
input from anyone of a number of input devices.

Consider the

following example (see Section 6.1 for description of real time
read .REALR command).
.REALR 1, Q,LNBUFl, 32, CTRLl, Nl

/REAL

.REALR 2, 2,LNBUF2, 42, CTRL2, N2

/TIME

.REALR 3, 3, LNBUF3, 36, CTRL3, N3

/READS

. IDLE
If .IDLE is reached before any of the input requests have
been satisfied, control is transferred to a lower priority FOREGROUND segment or to the BACKGROUND job.

The lower priority job

retains control un"til one of the FOREGROUND input requests is
satisfied.

Control is then returned to the FOREGROUND job by

executing the subroutine at the specified completion address
(CTRLl, CTkL2, CTRL3) and at the priority level specified by Nl,
N2, N3 which may be:
Value of N
Q

4
5
6
7

Level
Mainstream (lowest level)
Current level (level of ~EALR)
Software level 5
Software level 6
Software level 7

1-4

NOTE
If real-time reads (.REALR), real-time writes
(.REALW), or interval timer (.TIMER) requests
arc employed in the BACKGROUND, N may be set to
0, 4, 5, 6, or 7, but is converted to 0 since
the BACKGROUND job can run only on the mainstream level.
This allows the value of N to
be preset in cases where a BACKGROUND program
is to be subsequently run in the FOREGROUND.
1.2.2

Protection of FOREGROUND Core and 1/<2,.

The FOREGROUND job's core is protected by the Memory Protection Option
(Type KX09A).

The BACKGROUND job runs with memory protE~ct enabled;

the FOREGROUND job runs with memory protect disabled.
Protection of the FOREGROUND job's I/O devices is accomplished
via the hardware by the memory protect option, which prohibits lOT
and Halt instructions in the BACKGROUND area; and the software
since the Monitor and lOPS screen all I/O requests made via I/O
Macros.

Also, the Monitor and the BACKGROUND Loaders prevent

the BACKGROUND ~ob from requesting I/O which would conflict with
that of the FOREGROUND job (for example they would not honor a
BACKGROUND request for a paper tape handler being used by the
FOREGROUND job).

The Background/Foreground Monitor allows sharing of mUlti-unit,
mass-storage device handlers
d.mj

(such as, DECtape, Magnetic Tape,

ui sk Letwecn BACKGROUND and I;'OREGROUND jobs).

1-5

Using these

multi-unit handlers, n files can be open simultaneously, where
n equals the number of .DAT slots associated with the particular
bulk storaqe device.

Some multi-unit handlers require external

data buffers (assigned at load time) ,one for each open file.
These buffers are acquired from and released to a pool by the
handler as needed.
When this count is not accurate (because of the .DAT slots not
Doing used simultaneously), the keyboard command FILES (Section 2.5.2) can be used to specify the actual number of files
simultaneously open.

Both the FOREGROUND and BACKGROUND jobs

can indicate their file requirements by means of the FILES
keyboard command.
The multi-unit handlers are capable of stacking one BACKGROUND
I/O request.
operation

This provision is made to simulate exactly program

as it would occur under Keyboard or I/O Monitor (i.e.,

:lingle user) control.

Thus, control is returned to the BACKGROUND

JOD to allow non-I/O related processing when the handler is preoccupied with an I/O request from the FOREGROUND job.

For

example, if the FOREGROUND job has requested DECtape I/O with a
.READ, and is waiting for its completion on a .WAIT, control is
returned to the BACKGROUND job.

If the BACKGROUND job then re-

quests DECtape I/O with a .READ, the handler will stack the
request and return control to the BACKGROUND job following the
. READ.

The BACKGROUND job can then continue with non-I/O

related proccssinq asthouqh the .REl\D were being honored.

1-6

In hardware configurat.ions which include the Automatic Priori ty
Interrupt (API) option, the Background/Foreground Monitor allows
convenient use of software priority levels of the API by the FOREGROUND job.

The BACKGROUND job is permitted to use only the

mainstream level.
1.2.5

Use of Real-Time Clock

The Background/Foreground Monitor provides for convenient and
shared use of the system real-time clock.

It will effectively

handle many intervals at the same time; thus, the real-t:imc.
clock can be used simultaneously by both BACKGROUND and FORE·GROUND jobs.
Communication Between BACKGROUND and FOREGROUND ,Jobs

1.2.6

The Background/Foreground Monitor allows communication between
BACKGROUND and FOREGROUND jobs via core-to-core transfers.

'l'his

is accomplished by means of a special "Core I/O device" handler
within lOPS.

Complementing I/O requests are required for a core-

to-core transfer to be effected; for example, a FOREGROUND .READ
(.REALR) from core must be matched with a BACKGROUND .WRITE
(.REALW)

to corc.

Two possible uses of this feature are:
d.

rrhc~

BACKGROUND job could be related to the

FOREGROUND job, and as a result of its processing,

1-7

pass on information that would affect FOREGROUND
. 9rocessing, or vice-versa.
b.

The BACKGROUND job could be a future FOREGROUND
job, and the current FOREGROUND job, being its
predecessor, could pass on real-time data to
create a true test environment.

Communication between two jobs can also be done by storing
and retrieving data on shared bulk storage devices.
1.3

HARDWARE REQUIREMENTS AND OPTIONS
The following hardware is required to operate the Background/

Foreground Monitor System:
a.

Basic PDP-9 with Teletype,

Memory Extension Control, Type KG09A,

Additional 8192-Word Core Memory Module, Type MM09A,

Memory Protection Option, Type KX09A,

External Teletype System, including at least*:
(1)

One Teletype Control, Type LT09A or LT19A,

(2)

One Teletype Line Unit, Type LT09B or LT19B,

(3)

One Teletype, Model KSR33, KSR35 or equivalent**,

'*'l'he basic system Teletype is normally assigned to the BACKGROUND
environment.
One Teletype of the external Teletype system must be
reserved for the FOREGROUND job; additional Teletypes may be
assigned to either BACKGROUND or FOREGROUND functions.
If the
API option is available, a Type LT19A Teletype Control and a Type
LT19B Line Unit are recommended.
**Model 37 Teletypes are not supported. Model 33 or 35ASR Teletypes
are supported only to the extent that they operate as KSR's only;
their paper tape input and output facility cannot be used.
LT09's
and LT19's may not both appear in the same configuration.
1-8

Bulk Storage System, comprising either:
(1)

One DEC tape Control, Type TC02, and two DECtape
Transports, Type TU55 (three recommended), or

(2)

One Disk System, Type RB09

(and one DECtape

Control, Type TC02, and at least one DECtape
Transport, Type TU55), or
(3)

One Disk System, Type RF09/RS09

(and one

DECtape Control, Type TC02, and at least
one DECtape Transport, Type TU55)
The following options curr,:!ntly supported by software may
be added to improve system performance (as noted) :
Effect
Additional 8192-Word Core Memory
Modules, Type MM09B and MM09C
(to a maximum of 32,768 words)

Increase the maximum f:i ;~C' of
both BACKGROUND and FOREGROUND
programs that can be handled
by the system.

Automatic P~iority Interrupt,
'I'ype KF09A

Allows for quicker recognition
of requests for service by I/O
devices.

Extended Arithmetic Element,
Type KE09A

Increases speed of arithmetic
calculations.

Additional DECtape Transports,
Type TU55, or IBM-compatible
Magnetic Tape Transports, Type
TU20 or TU20A and Tape Control
Type TC59

Allows greater bulk storage
capability, simultaneous use
of storage media by more
programs.
Since only one file
may be open at a time on IBMcompatible magnetic tape transports, more than two Type TU20
or TU20A transports may be desirable for some applications.

1-9

Automatic Line Printer, Type 647

Provides greater listing capabilities.

200 CPM Card Reader, Type CR03Bl

Allows card input and control
cards for BACKGROUND Batch
processing.

Additional Teletype Line Units,
Type LT09B, (or LT19B) and Teletypes, Type KSR33, KSR35 or equivalent** (up to a maximum of 1610
LT09B or LT19B units, requiring
four LT09A or LT19A controls) .

Provides additional output
devices if multiple FOREGROUND
jobs may require simultaneous
output or BACKGROUND jobs wish
to use multiple devices.

1
The Type CROlE and Type CR02B Card Readers, although no
longer sold by the Company, are supported by software in
the BACKGROUND/FOREGROUND System.

Note:

The 339 Programmed Buffered Display is supported by
software.

1-10

SECTION 2
BFKM9 - NON-RESIDENT BACKGROUND/FOREGROUND MONITOR
2.1

INTRODUCTION
BFKM9 is the title of the non-resident portion of the

Background/Foreground Monitor.

It is identical in nature to

the Keyboard listening section of the Keyboard Monitor, with
which the reader is assumed to be familiar.

BFKM9 reads and

interprets commands typed by the user at a control teletype
(there is one Background control teletype and one Foreground
control teletype).
There are three kinds of commands which the user may
type:

2.2

Requests for information, such as, a directory
listing of unit ~ of the system device;

Allocation parameters, such as, core size,
number of open files, and I/O devices to be used;

Load a system or user program.

LOCATION AND WHEN CALLED
BFKM9 is loaded from register 12000 of the highest core

bank to the top of memory and iB transparent to the user
since it is always overlayed.
When the Background /Foreground system is loaded or reloaded to start a new Foreground job, the Resident Monitor is
first loaded into lower core from unit

of the system device,

either by use of the paper tape bootstrap or by typing CTRL C
at the' Foreground control teletype.

The Resident Monitor then

brings the Non-resident Monitor into the top of memory.

2-1

When

operating in the Foreground, BFKM9 runs with memory protect
disabled.
After the Foreground user program has been loaded and has
started to run, the Non-resident Monitor is re-loaded, with
memory protect enabled, to converse with the user at the
Background control teletype.

BFKM9 is also re-loaded whenever

the Background job exits or the user types CTRL C at the
Background control teletype.
In both the Foreground and Background, after the user has
given a command to load a program, the Non-resident Monitor
brings the System Loader into memory from the system device,
overlaying the Non-resident Monitor.
2.3

INITIAL OPERATION
When BFKM9 is started for the Foreground job, it must

perform some initialization of which the following is of
interest:
a.

Set the contents of .SCOM+25 to 2. This sets
the initial size of free core to be allotted
to the Foreground job, in addition to the space
required by the Foreground user programs. The
user may assign more free core by issuing the
FCORE command, described in section 2.5.3.

BFKM9 checks the entire Foreground Device Assignment Table (.DATF) to see if any of those
.DAT slots request the teletype handler and
the unit number currently assigned to the
Background control teletype.
If so, those slots
Qrc changed to the Foreground control teletype
Qnd a message is output as in the following
example.

2-2

EXAMPLE 1:

The Foreground control teletype is TTl,
the Background control teletype is TT~,
and the initial contents of .DATF slots
1 and 3 refer to TTA~.
.DATF slots 1
and 3 will be changed to refer to TTAI and
the following message will be printed on
the Foreground control teletype:
FGD .DATS CHANGED TO TTAl:
1

FKM9 VIA
$

The Non-resident Monitor identifies itself
to the Foreground user by printing FKM9 VIA
and types $ whenever it is ready to accept
a command.
When BFKM9 is started for the Background job, it performs
initialization of which the following is of interest:
a.

It builds the initial configuration of the Background . DAT table (. DA,]~B). Any. DATB slots which
request a single user version of a device handler
(for example, DTB or DTC) will be changed to the
multi-uni t handler (DT1~ in this case) if it is
already in core for the Foreground job or if it
is the resident system device handler.

BFKM9 will check all Background .DAT slots to
make certain that they do not conflict with Foreground I/O. The Resident Monitor contains, for
this purpose, a table (.IOIN) which lists all
I/O handlers and unit numbers in use. The following occurs:
(1)

If a handler for this I/O device is not
already in core, the Background .DAT
slot is left untouched.

(2)

If a single user handler for this device
is already in core for use by the Foreground job, by definition the Background
job may not use this device. Therefore

2-3

the Background .DAT slot is cleared (set
to zero).
(3) If the multi-unit handler for this device
is in core, but the device unit number in
question is not assigned to the Foreground
job, Background is allowed to share that
handler.
Unit ~ of the system device may
always be used by the Background job.
(4) If the Background .DAT slot requests a
multi-unit handler and unit number already
assigned to the Foreground, normally this
is illegal and that .DAT slot will be
cleared. However, some users may wish to
allow both jobs to access the same unit.
This is permitted only for bulk storage
devices (DECtape, Disk, etc.) provided
that the Foreground user typed the command
SHARE, explained in section 2.5.7.
If the initial Background .DAT table was altered by clearing .DAT slots for the reasons given above, a message will be
output to the Teletype as in the following example.
EXAMPLE 2:

The Foreground job is running and has been
assigned device handlers and unit numbers
DTA1, DTA2, TTA1, TTA2, and LPA (line
printer handler - not shareable).
The
initial Background .DAT table contains
conflicting requests as follows:
.DAT SLOT

CONTENTS

-IS

DTAI

-12
-4

LPA~

DTA2
TTA2

The following will be printed on the Background control teletype when BFKM9 is £irst
loaded:
BGD .DATS CLEARED BECAUSE OF FGD I/O:
-15 -12 -4 3
FCONTROL

TTAl

2-4

FGD DEV-UNITS:
TTA2
DTAI
DTA2
BKM9 VIA
$

FCONTROL indicates which unit is the Foreground
control teletype. The remainder of the message
indicates what I/O is being used by the Foreground job. The Monitor identifies itself to
the Background job user as BKM9 VIA and signals
that it is ready to accept a command by printing
$.
2.4

INFORMATION COMMANDS
The following information commands exist in Background/Fore-

ground:
USE
To print a comment
To examine .DAT slots
To obtain a directory listing
To list information about core
and I/O in use by the Foreground.

COMMAND
LOG
REQUEST
DIRECT
IN USE

2.4.1

The LOG Command (L)

This command is legal in both Foreground and Background and may be
abbreviated by the single leti:er L.
on the Teletype.

It is used to record comments

Unlike all other commands, LOG is terminated only

by the character ALTMODE, so 1:hat multiple comment lines may be
typed.
LXAMPLE 3:
$ LOG
THIS LINE)
AS WELL AS THIS ONE)
AND THIS ONE ARE IGNORED Q\LTMOD~
$
2-5

2.4.2

The REQUEST Command (R)

This command is legal in both Foreground and Background and may
be abbreviated by the single letter R.

It is used to examine

the contents of all or part of the user's .OAT table.

The Fore-

ground user may examine only the Foreground .OAT table and the
Background user only the Background .OAT table.

This requests a printout of the entire .OAT table.

No example

is given since R is essentially the same request as in the
Keyboard Monitor System.
FORM 2:

RuUSER)

This requests a printout of the contents of all the positive
numbered .OAT slots.

The result, again, is the same as in the

Keyboard Monitor System.
FORM 3:

RuXYZ~

Here, XYZ stands for the name of a system program; e.g., MACRO,
PIP, F4, LOAO, etc.

The names given must be identical to those

used to load the programs.

The information printed, as in the Keyboard

Monitor System, is those .OAT slots used by the given system program.
Since, at present, the only system program load commands allowed
in the Foreground are LOAD, GLOAO, PIP and EXECUTE, only these
four may be used in Foreground REQUEST commands.

2-6

FORM 4:

Ru.DATuj, k, 1, ...

, r, s)

Here, j, k, .1, etc., are .DAT slot numbers.
EXAMPLE 4:
$R u .DATw -3, -1, 4, 7}

TTAI DTA2 NONE

LPA~

2.4.3

The DIRECT Command (D)

This command is legal in both Foreground and Background and
may be abbreviated as D.

The format is:

Dun)
where n = a unit number

through 7) on the system device.

Directory listings have been altered in BFKM9 to print the
number of free blocks before

thE~

file names.

The background

user may not request directory listings of any units owned
by the Foreground job unless the Foreground user typed the
SHARE command (see below).
2.4.4

The INUSE Command (I)

rrhis command is legal only in the Background and may be abbreviated by the single letter I.

It causes the Monitor to print

the first free core location above the Foreground job, the
Foreground control teletype unit. number and any other I/O
used by Foreground.

2-7

EXAMPLE 5:
$ I)

1ST REG ABOVE FGD

323.01

FCONTROL = TTA2
FGD DEV-UNITS:
DTAI
LPA.0
$

2.5

ALLOCATION COMMANDS
The following commands assign parameters, control and

conditions:
COMMAND
ASSIGN
FILES
FCORE
FCONTROL
BCONTROL
NEWDIR
SHARE
NOSHAPE
7CHAN
9 CHAN
VC38
MPOFF
MPON
2.5.1

PURPOSE
To assign I/O handlers to .DAT slots
To specify handler file capacity
To set up Foreground free core
To select Foreground control teletype
To select Background control teletype
To write a new file directory
To allow jobs to share same I/O units
To nullify effect of SHARE
To specify 7-channel MAGtape operation
To specify 9-channel MAGtape operation
To load the VC38 character table
To let Background access all of core
To nullify effect of MPOFF

The ASSIGN Command (A)

This command is legal in both Foreground and Background and may
be abbreviated by the single letter A.

Its format and function

are, with a few exceptions, identical to the same command in the
Keyboard Monitor System.

2-8

The format is:

AuDDLNum, n, •.. , pi ... IDDLNum, n, •.. ,

where DD stands for the two letter device

name~

e.g., DT

for DECtape, LP for line printer, etc.
L is the third letter of a device handler name and is optional.
If not given, the letter A is

assumed~

e.g., DTI

= DTAI.

The

"A" version of a handler is the multi-unit, shareable handler,
provided that one exists.

LPA, for example, is not a multi-

unit handler.
N is the unit number to go with the device handler and is
also optional.
= DTA~.

If missing, N is assumed to be g, e.g., DTA

Therefore, DT = DT.0 = DTA =

... , p stand for .DAT slot numbers.

DTA~.

The letters m, n,

The slash (I) separates

handlers.
To clear out a .DAT slot, assign NONE to it.

If any error

is detected in the command, none of the assignments will be
made.
The Foreground and Background users may make assignments only to
their respective .DAT tables.

Foreground may not assign TTA.0

if, for example, that is the Background control teletype.

Since

DTA is permanently in core with the Resident Monitor (assuming
that DECtape is the system device) DTB, DTC, etc., when assigned,
will automatically be changed to DTA.

This applies as well to

ll<.lIlUlcr assignments made in the Background whenever the multiunit version of the handler is in core for Foreground use .

.2-9

Background .DAT slot assignments are tested to insure that they
do not conflict with Foreground I/O, as explained in section 2.3.
Whenever the Monitor detects such a conflict, it will print the
message:
OTHER JOB's DEV-UNIT
To insure that no conflict can occur when assigning the coreto-core handler, COA., the unit number, independent of what
the user typed, is set to

for Foreground and 1 for Background.

The core-to-core handler disregards the unit number.
2.5.2

The FILES Command (F)

This command is legal in both Foreground and Background and may
be abbreviated as F.

The purpose of this command is to save

core space by limiting the number of I/O buffers assigned to multiunit device handlers.
The format of the FILES command is:

where DD stands for the multi-unit handler or device name (e.g.,
DTA or DT) and N for an octal file count.
EXAMPLE 6:

Assume that the Foreground user programs are being
loaded into core by the Foreground Linking Loader
and that these programs use .DAT slots 1 through l~.
(.IODEV 1, 2, 3, .•.. , l~).
Further, assume that
all l~ slots were assigned to DECtape, DTAn (the
unit numbers are unimportant to this discussion).

2-10

Most multi-unit handlers, DTA being one of
them, require that I/O buffers be assigned to
them externally.
This is done by the various
loaders.
In this example, the Foreground Linking Loader, seeing that no FILES command was
given for the handler DTA, must assume that the
user wants l~ files open simultaneously.
This
will require l~ buffers, each 6~S octal words
in size.
The FILES command is used to tell the loaders
to assign a given number of buffers for a
particular mUlti-unit handler based on the
maximum number of files that the user programs will
have open simultaneously.
Each multi-unit handler
has a maximum open file capacity; for example, DTA
may have up to 2~ octal.
If IS I/O buffers are
assigned for DTA in the Foreground, then only up
to IS may be assigned for Background.
The FILES
command issued in ·the Foreground specifies only
Foreground I/O buffers.
Thus, to limit the
number of I/O buffers assigned to the Background,
the FILES con~and, for the same multi-unit device,
must also be issued in the Background.
At load-time, I/O buffers are set aside in core by the Loaders.
The buffers are recorded in a table within the Resident Monitor,
. BFTAB , but are not flagged for the exclusive use of particular
device handlers.

A-t

run-time,

E~ach

multi-unit handler which needs

a buffer must request a buffer from the Moni tor.

The handler must.

also release the buffer to the pool when i t is no longer needed.
The resident buffer, permanently assembled into the Resident
Monitor, is always available to the Background job.

This buffer

is assumed to be as large as the largest I/O device buffer
(6~S

octal words) .

In the event that the Background job were to

.IODEV only one .DAT slot whjch is linked to a multi-unit handler

2-11

that requires external buffers,
could save

6~~

(DTA. for example) the user

registers by typing:

$FILESuDTu~'

That is,

assign one less buffer than is needed.
In the FILES command, the pseudo-device

is recognized.

size of the external buffer for this pseudo-device is
octal.

The

l~~

Some functions in multi-unit handlers may require a

smaller buffer size than others.

If the user were only to use

the former function type, he could type, for example,
and $FILES .. n.

$FILE~DTw~

In DTA., .TRAN and .MTAPE commands only require

the smaller buffer.
2.5.3

The FCORE Command

This command is legal only in the Foreground and may not be
abbreviated.
The format of the FCORE command is:
FCOREwN ~
where N is the amount (in octal) of free core requested for
the Foreground job.
~s

in the Keyboard Monitor System, unused (free) core is defined

the address pointers in the registers .SCOM+2 and .SCOM+3,

the lowe[:i t and the highes t free core location, respectively.
Since both the Foreground and the Background jobs have their
own separate free core areas, the values in .SCOM+2 and .SCOM+3
are changed appropriately whenever control passes from one job
to ·the other.

2-12

The FCORE command allows the Foreground user to specify how
much free core his program will need, in addition to that
required to load his program.

It is possible for all of core

to be assigned to Foreground.

This means, however, that there

will be nc room for Background to run, which is perfectly
legal.

If -this is the case, the message:

SORRY, NO ROOM FOR BGD
is printed on the control teletype:
2.5.4

The FCONTROL Command

This command is legal only in the Foreground and may not be
abbreviated.

It is used to transfer the control teletype to

some other teletype unit.
The format of the FCONTROL command is:

where N is the number (octal) of any teletype on the system.
If N is already the Foreground control teletype, the command is
ignored.

If N is the current Background control teletype, the

two teletypes are swapped but no message will be printed to this
effect.

Changing the Background control teletype may affect

Foreground .DAT slots and an appropriate message will be printed
on the Foreground control teletype.

Th~s

the next section on the BCONTROL command .

.2 --13

is fully explained in

Wh(~n

FCONTROL changes the Foreground control teletype, the

following action takes place:
a.

The following message is printed on the old
control unit:
CONTROL RELINQUISHED
ABORT

The system is reloaded from the system device.

The Monitor prints
FKM9 VIA
$

on the new Foreground control unit and is ready
to accept commands there.
2.5.5

The BCONTROL Command

This command is legal both in the Foreground and in the Background
and may not be abbreviated.

It is used to transfer the Background

control teletype to some other teletype unit.
The format of the BCONTROL command is:
BCONTR°LuN)
where N is the number (octal) of any teletype on the system.
This command is illegal and is ignored if unit N belongs to
the Foreground job.

Even though unit N may have been assigned

to a Foreground .DAT slot, it does not belong to the Foreground
job unless it happens to be the Foreground control teletype
or unless the Foreground user programs contained an .IODEV to
that .DAT slot.

This command is also ignored if unit N is

already the Background control teletype.

2-14

If BCONTROL is issued in the Foreground or if the Background
control telE2type is changed because of an FCONTROL command,
all Foreground .DAT slots which now refer to the new Background
control unit will be changed to the Foreground control unit
to avoid I/O conflict.

Should that situation occur, the fol-

lowing example shows what would be printed on the Foreground
control unit:
FGD .DATS CHANGED TO TTAI
-6 2 7

If BCONTROL is issued in the Background, the followinq action
takes place:
a.

The following message is printed on the old
control unit:

CONTROL RELINQUISHED
b.

tc is printed on the new unit,

The Non-resident Monitor (BFKM9) is reloaded for
Background from the system device

The Monitor prints
BKM9 VIA
$

on the new Background control teletype and is
ready to accept commands there.

This command is legal in both Foreground and Background and may
be abbreviated by the single letter N.

.2-15

Just as in the Keyboard

Monitor System, this command allows the user to write a new
file directory on some unit of the system device.

However,

space will not be reserved for a tQ (CTRL Q) area.
The format of the NEWDIR command is:
NwM~

where M is some unit number (octal) on the system device.
Unit

may not be used.

The Background may not write a new

file directory on a unit that belongs to the Foreground
unless the Foreground has issued the SHARE command (see below).

This command is legal only in the Foreground and may be abbreviated by the single letter S.

Its purpose is to allow the

Background job to assign and to use the same units of any I/O
devices that belong to the Foreground job, provided that they
are bulk storage devices

(DECtape, Disk, Magtape, etc.) and

that the device handlers are the multi-unit versions.

The user

must be careful when allowing this condition to occur.

The "tape"

could be fouled i f

~~_-t:~.

jobs were to try to use the same uni t

for output at the same time.

The SHARE command also removes the restriction that the Foreground
user program may not use unit

on the system device.

this unit is reserved for the Background.
The format for this command is:
SHARE~

2 --16

Normally,

2.5.8

The NOSHARE Command

This command is legal both in Foreground and in Background and
may not be abbreviated.

It nullifies the effect of any pre-

vious SHARE command; i. e.,

dOE~s

not allow the Background to

share device units with the Foreground.
When NOSHARE is issued in the Background it may cause some
Background . DAT slots to be cleared.

message, as in Example 2,

will be printed to that effect.
The command format is:
2.5.9

NOSHAR.E)

The 7CHAN Command (7)

This command is legal only in the Foreground and may be
abbreviated by the single character 7.

The effect of this com-

mand is to clear bit 6 in .SCOM+4 to inform the Magtape device
handlers that the default assumption is 7-channel operation.
The format of the 7CHAN command is:
7CHAN)
2.5.10

The 9CHAN Command (9)

This command is legal only in the Foreground and may be
abbreviated by the single character 9.

It sets bit 6 in

.SCOM+4 to inform the Magtape device handlers that the
default assumption is 9-channel operation.

2-17

The format of the 9CHAN command is:
9CHAN )
2.5.11

The VC38 Command (V)

This command is legal in both Foreground and Background and may
be abbreviated by the single letter V.

No action is taken until

a command has been given to load a program.

At that time, if

the VC38 command was given, the Non-resident Monitor will seek
and load the file VC38TB DMP from unit fO of the system device.
The VC38

c~aracter

table is used in conjunction with the 339

display handler, DYA., when the system does not have a VC38
hardware character generator.
The table is loaded into core such that its base address is a
multiple of

l~fO~

octal.

The base address is stored as the

first word in the 339 Pushdown List.

The address of the Pushdown

List is in .SCOM+12.
The VC38 command given in the Background will be accepted but
ignored if the 339 display handler is assigned to the Foreground.
The format of the VC38 command is:
VC38)

2-18

2.5.12

The MPOFF Command

This command is legal only in i:he Foreground and may not be
abbreviated.
Format:
MPOFF}
Normally, Background may not modify nor transfer to registers
within the Resident Monitor and the Foreground job; it also
cannot issue rOT's.

The MPOFF command signals the Resident

Monitor to set the hardware protect bound to zero and also
allows Background rOT's to be issued.
2.5.13

The MPON Command (M)

This command is legal in both Foreground and Background and
may be abbreviated by the letter M.
Format:
MPON)
The MPON command nullifies the effect of MPOFF, thereby
protecting the Foreground job from the Background job in
the normal manner.

2-19

2.6

PROGR~M

LOAD COMMANDS

In the Foregound, only four load commands are legal:
LOAD), GLOAD) , PIP) 'and EXECUTE u XXX).
viated by the single letter E.

EXECUTE may be abbre-

LOAD and GLOAD have the same

meaning and effect as in the Keyboard Monitor System.
The following program load commands exist in the Background:
PATCH;
CHAIN)
F4)
F4A}
EDIT)
PIP)
EXECUTEuXXX)

2.7

LOAD)
GLOAD}
DDT)
DDTNS)
SGENl
DUMP-)
UPDATE) "
CONV)

FINAL OPERATION
After BFKM9 has received a program load command from

either the Foreground or Background, it will bring the System
Loader (.SYSLD) into the top of core overlaying BFKM9.

In the

Foreground, .SYSLD is actually the Foreground Linking Loader.
In the Background, .SYSLD loads Background System Programs,
including the Background Linking Loader.
2.8

CONTROL CHARACTERS
While control is in BFKM9, the user may type CTRL P

to terminate execution of the current command and to restart.
Restart in this manner does not nullify the effect of

2-20

previous ly executed commands;

€!. g .,

wi 11 not reset the . DAT

table to its initial configuration.

To reload the Monitor for

the current job, the user may t:ype CTRL C.
2.9

LEGAL
IN
F B
F B
F B
F
F
F B
B
F B
F B
F B
F B
F
F
F
F
F B
F B

B
B
B
B
B
B
F B
B
B
F B
F B
B
B
B
F 13
13
13

SUMMARY OF COMMANDS

ABBREVIATION
A

COMMAND EXAMPLE
DTu- 4 )
ASSIGNuDTAl u 2, 3/TTlwl,
BCONTRO~2)

F
I
L
N
R
S
7
9
M
V

DIRECTu .0')
F CONT ROLu.lJ
FcoREu14.0't)
FILE SuDTu 3)
INUSE)
LOG u . . . . . .. €LTMOD~
NEWDIRa..,S)
NOSHAREj
REQUES~XXX) or REQUESTuUSER)or
REQUEST u .oAT j ,k, 1) or REQUEST).
SHARE)

~g~~~.•.

MPO~~)
MPON}
VC38)

CHAIN)
CONV)
DDT)
DDTN~
DUMP)
EDIT)
EXECUTEuXXX)
F4)

F4A)
GT.JOAD)
LOAD)
Ml~CRO)

Ml~CRO~J
PATCHI
PIP)

SGEN)
UPDATE)

2-21

SEc'rION 3
CONTROL CHARACTERS
3.1

PURPOSE
Control characters are single characters typed by the user

at a teletype which request special action by the Monitor.
Except for the character RUBOUT, all control characters are
formed by holding down the control key CTRL while striking the
appropriate letter key.
The characters CTRL U and RUB OUT are used as "erase"
characters during teletype input or output.

CTRL C, CTRL P,

CTRL S, and CTRL T are used to interrrupt the operation of
the current program and to transfer control elsewhere.

CTRL R

is used to restart I/O after a not-ready condition has been
detected for some device.

CTRL Q stops the current job and

dumps memory onto a specified area of some unit of the system
device.

CTRL D effects an end-of-file condition during tele-

type input.
3.2

CONTROL TELETYPE
In the Background/Foreground System, which may accommodate

up to 17 (decimal) teletype units, two teletypes are designated
as control teletypes (one for Background and one for Foreground).
Initially, it is assumed that unit ~ (the console teletype) is
the control teletype for Background and unit 1 is the control
unit for Foreground.

3-1

Control teletypes differ from the other units in two ways:

3.3

They are used to converse with the Non-resident
Monitor and system programs in order to set up
parameters and conditions for a job and to initiate the loading and execution of programs.

Certain control characters are recognized only
at control teletypes; i.e., are ignored if they
are typed on the other teletype units (see section 3.4 and following).

TELETYPE HANDLER
The multi-unit teletype handler (TTA) which is imbedded in

the Resident Monitor, makes special tests for control characters
when it

re~eives

typed input.

Normally, when no .READ request

has been issued to a teletype, characters received from that
unit are ignored unless they are control characters.

A descrip-

tion of the action taken in each case is given in the following
paragraphs.
3.4

CTRL C (tC)
This character is ignored unless typed at a control tele-

type.

It will be echoed to the teleprinter as tC.
If CTRL C is typed at the Background control teletype, the

Background job will be aborted and the Non-resident Monitor will
be loaded to start a new Background job.

Foreground is not affec-

ted.
CTRL C typed at the Foreground control teletype aborts both
the Foreground and the Background jobs.

3-2

In this case, the entire

system is restarted; that is, the Resident Monitor and the Nonresident Monitor are reloaded to start a new Foreground job and
the message ABORT is printed on the Background control teletype.
3.5

CTRL 5 (t5)
CTRL 5 is recognized only at a control teletype and,

specifically, only after the Monitor has printed t5.

This is

the result of loading a user program by giving the 'command $LOAD
(instead of $GLOAD)to the Non-resident Monitor.

Both commands

bring in the Linking Loader to load user programs.
LOAD-AND-GO.

$GLOAD means

$LOAD means load the user programs, signal the

user that this has been done (by printing t5), and then wait for
the go-ahead signal (when the user types CTRL 5) .
This feature allows the user to set up I/O devices before
starting his program.

When CTRL 5 is typed by the user and is

accepted by the Monitor, t5 is echoed back to the teleprinter.
3.6

CTRL T (tT)
This character is recognized only at the Background control

teletype when the user has called in the system program DDT.

When

CTRL T is typed and accepted, it is echoed to the teleprinter as tT.
CTRL T provides a means of interrupting the execution of a
user program and transferring control to DDT.

When CTRL T is

typed, the Monitor saves the status of the Link, extend memory,

3-3

and memory protect along with the interrupted PC in .SCOM+7
so that DDT will be able to return control to the user program
at the point at which it was interrupted.

The contents of

the AC at the time of interruption is returned in the AC and
saved by DDT.
3.7

CTRL P (tP)
CTRL P is the interrupt and restart character available

to user and system programs.

When it is typed on some teletype

and is accepted by the Monitor, tP is echoed to the teleprinter
on that unit.
fn

the Background/Foreground system there are two types

CTRL P functions:
1)

NORMAL CTRL P and

REAL TIME CTRL P.

The two CTRL P functions are described, individually, in paragraphs 3.7.1 and 3.7.3.
Setting a CTRL P restart address (ADDR) is accomplished by
issuing the I/O MACRO .INIT to any .DAT slot linked to the
Teletype handler.
The format of the .INIT macro is:
.INIT A,M,P+ADDR
which is expanded by the MACRO assembler into the following
machine code:

3-4

LOC
LOC+l
LOC+2
LOC+3
where A
M

CAL M8 +A 9 _ 1 7
1

P+ADDR g

a .DAT slot number (octal radix)
transfer mode

ADDR

Input

Output

a IS-bit address (octal) of a restart point in
the program or of the entry point of a closed
real-time subroutine.
Normal CTRL P
Mainstream (REAL-TIME)

lfOJl~JlfO

priority code

2fOfOfOJlfO
3fOfOJlJlfO
4 50 JlJl 5050
SfOfOJlJlJl
6 JlJlfOJlfO
7 50 fOfO JlfO

No chanqe to CTRL P
Priority level of the .INIT
API level S
API level 6
API level 7

Background requests to an l\.P I level (4JlfOJlYffO - 7 fOfOfOJlfO) wi 11 be
converted to Mainstream since Background programs cannot use the
API software levels.
3.7.1

NORMAL CTRL P

A .INIT to set up a NORMl\L CTRL P

(priority code 50) may be

done only to a control teletype.

NORMl\L CTRL P was so named

because the action taken when the user types CTRL P is nearly
the same as in the Keyboard Monitor System.
When a control teletype has been set up for a NORMAL CTRL P
and that character is typed by the user, the teletype handler

3-S

will abort all Teletype I/O for that job (Background or Foreground).

The Monitor will, when control is at Mainstream,· save

the status of the Link,extend memory, and memory protect with
the interrupted PC in .SCOM+IO

(whose contents are swapped in

and out for Background and Foreground), return the interrupted
AC to the AC, and transfer control to the restart address ADDR
as specified by the last .INIT.
Note:

When the Monitor processes a CTRL T or a NORMAL
CTRL P, it kills any pending mainstream realtime routines to be run by zeroing the contents
of .SCOM+S7 (Foreground) or .SCOM+61 (Background).
The user's program (if NORMAL CTRL P) or the user
(if .CTRL T) must zero the entry points of all his
mainstream real-time routines.
CTRL P and CTRL T
do not affect API level real-time requests.

If the restart address ADDR = ~, CTRL P to the given teletype
will be disabled; i.e., ignored if typed (except if P =
3.7.2

3~~~~~).

No Change

If .INIT for a given teletype unit contains the priority code
3~~~~~,

the restart address is ignored and the status of CTRL P

to that unit is not changed.
3.7.3

REAL-TIME CTRL P

A .INIT to set up a REAL-TIME CTRL P may be done to any teletype
unit.

When so set up and the user types CTRL P, I/O to that

teletype is aborted.

Control eventually goes to a closed real-

time subroutine, ADDR, at the priority level defined by P,

3-6

in the same manner as for a

.REALR,

.REALW or .TlMER

request.
If the restart address ADDR

CTRL P to the given tele-

type will he disabled; i.e., ignored if typed.
REAL-TIME CTRL P is useful for multi-user programs, for instance,
multi-user FOCAL, where each teletype has the ability to interrupt
and restart.
3•8

CT RL R

( t R)

In the Background/Foreground system, I/O device handlers
which detect a not-ready condition will request the Monitor
to print a message on the appropriate control teletype.

The

line printer handler message, for instance, would be:
LP~

NOT READY

The unit number has no significance for the line printer.
Some single-unit handlers, such as the card reader handler, use
the unit number designation to indicate the cause of the not-ready
condition.

After the message has been printed, the user should

ready the device and then type CTRL R, which is echoed as tR.

I/O

for that device is then resumed.
While the Monitor is waiting for the user to type CTRL R,
the user's program continues execution provided that it is not
huruj

up waiting for completion of I/O from the not-ready device.

The Monitor can handle one not-ready condition per job.

Should

a second not-ready request occur while another is being processed,

3-7

job execution will be aborted with a .ERR ~~4 terminal
error.
3. 9

CTRL Q (tQ)
CTRL Q may be typed at any time, but it is ignored if it

is not issued at a control teletype.
The purpose of typing CTRL Qis to stop program execution
and to dump all of core memory onto a specified area of some
unit on the system device.

The dump starts with block

l~l

octal

on the given unit and overlays any data that may have existed
in that area on the output device.
octal blocks

(1~1-2~~);

a 32K system;

2~~

A 16K system will dump

a 24K system,

octal blocks

14~

octal blocks

l~~

(l~l

24~);

(1~1-3~~).

To insure that CTRL Q will not overlay useful data, the user
must employ the

system program PIP to write a new file direc-

tory on that unit, using the (S) switch to reserve space for
CTRL Q.

For example:

>NuXXuu(S) )

where XX is the device name and

u the unit number.

Note that

the size of the CTRL Q area reserved is based on the amount of
core existing in the system in which the new directory is written.
The area reserved on a DECtape in a 16K system is not sufficient
to do a protected CTRL Q in a 24K or 32K system.
3-8

When the Monitor accepts CTRL Q, it first terminates
execution of the job (Foreground if Foreground CTRLQ, Background if Background CTRL Q).

This involves calling all

device handlers tied to that job to stop I/O, clearing all
Monitor queues of entries for that job and disabling all
control characters for that job except CTRL C.
The Monitor then prints tQ on the appropriate control
teletype and reads one character.

The user must then type the

number of the unit on which the dump is to occur.
may not be used.

Unit zero

If the SHARE command is not in effect, a

dump may not be done to a unit vlhich belongs to the other
job.

If the Monitor rejects

thE~

typed character, it prints

tQ again and waits for another character.
When the unit number is accepted, the dump takes place;
then the Monitor is automatically reloaded.
CTRL Q does not affect Foregrourid.

A Background

A Foreground CTRL Q, on

the other hand, aborts the Background job.

It is not possible

to load and restart a core dump in Background/Foreground.
3.l~

CTRL U (@)
CTRL U may be typed at any teletype unit.

If a .READ or

.REALR was issued to some teletype and the user decides he
wants to "erase" everything he has typed for that read request,
he may type CTRL U, which will be echoed to the teleprinter as @.

3-9

The .READ or .REALR will still be in effect and he may then
retype the input.
While output to a teletype is being done as a result of a
.WRITE or .REALW, the user may type CTRL U to terminate the
write.

In this case nothing is eChoed to the teleprinter.

3.11 RUB OUT

This character is recognized only while the user is
typing input to satisfy a .READ or .REALR request.
typed, RUBOUT deletes the last input character.

When

For example,

if the US2r has typed ABC and then RUBOUT, the C will be
"erased".

If he now types another RUBOUT, the B will be

"erased".

Every time a character is so removed, the character

is echoed to the teleprinter.
3.12

CTRL D (tD)
The character CTRL D is recognized at all teletypes and

is echoed back as tD.

When typing input, CTRL D effects

an end-of-file condition by terminating the .READ or .REALR
request and storing the end-of-file,
buffer header.

~~1~~5,

in the input line

Since the word pair count returned is a

any

characters typed prior to the CTRL D for the same read request
will be lost.
3-10

SECTION 4
LOADERS
4.1

INTRODUCTION
There are three program Loaders in the Background/Foreground

system.

On the system file directory they are listed as .SYSLD SYS,

BFLOAD BIN and EXECUT BIN .
. SYSLD is an absolute system program that functions as two
loaders:

when it is called in for Foreground loading, it is the

Foreground Linking Loader; when it is called in for Background
loading, it is the Background System Program Loader.

BFLOAD is the

Background Linking Loader.
EXECUTE operates in both Foreground and Background as a loader
of overlay programs

(XCT files) built by the CHAIN system program.

A description of CHAIN and EXECUTE is given in the utility manual.
4.2

FOREGROUND LINKING LOADER
Link loading of the Foreground job is initiated by typing GLOAD

(Load-and~Go)

or LOAD (Load-and-·Pause) to the Moni tor at the Fore-

ground control teletype.

The Foreground Link Loader (.SYSLD) is

then brought into the top of memory, overlaying the Non-resident
Monitor.

The following message will then be printed:

FGLOAD VIA
>

The;.,. signals the user that he may now type in his command string.
The command string format is nearly 'the same as for the
Linking Loader in the Keyboard Monitor System.

4-1

The only

change is the addition of memory map options, which must precede the list of user program names.

The format is as follows:

>options+mainprog, others, ... ALTMODE
4.2.1

Option Characters And Their Meanings
Character
P

4.2.2

Meaning
Print program names and their assigned relocation
factors

Print common block names and their assigned
locations

Print global symbol names and their definitions

Use of + Terminator
Prior to the terminator + all characters except option

characters are ignored.

Carriage return preceding the + starts

a continuation line headed by>.

ALTMODE preceding the +

restarts the Loader; therefore, no loading is done unless the
character + appears in the command string.
If no option characters precede the +, the default assumption
is that no memory map is to be printed.
After the +, type the program names (main program first - no
extensions) separated by comma or carriage return.
the command string with ALTMODE.

Terminate

Before the terminating ALTMODE

has been typed, the Loader may be restarted by typing CTRL P.

4-2

4.2.3

Sequence of Operation

Once the command string has been accepted, the Loader will perform
the following sequence of operations:
a.

Load all user programs, specified in the command
string, from .DATF -4. These programs are loaded
from the bottom of core up, starting at the top
of the Resident Monitor.
Calls to external library
routines via .GLOBL, co:mmon block definitions,
and . IODEV requests are-' saved in the Loader's
symbol table, built fro:m the bottom of the Loader
down.
Programs containing executable code (which
excludes BLOCKDATA subprograms) are relocated such
that they do not overlap core bank boundaries.

If a library search is necessary and the contents
of .DATF -5 is non-O, the Loader will seek the user
library, .LIBR BIN, via that .DAT slot, and will
load all requested library routines which it finds.
I/O device handlers mus-t not be in the user library".

If a library search is still necessary for non-I/O
routines, the Loader will search the system arithmetic Library, .F4LIB BIN, via .DATF -7 in the same
manner as above.
I/O device handlers must not be
in .F4LIB.

If any I/O handlers must be loaded, the Loader
searches through the system I/O Library, .IOLIB BIN,
via .DATF -7. After this has been done, program
loading has terminated.

At this point, all undefined common blocks are
defined and assigned core space.
Common blocks
are allowed to overlap core banks.

If t.here are still some undefined global symbols,
they will be matched with common block names and,
if a match is found, defined as the base address
of the matching common block.

For aLl mUlti-unit device handlers in use for
the user's programs, external I/O buffers are
assigned core space (if necessary) and recorded
in .BFTAB within the Resident Monitor. The number
of such buffers depends on the $FILES counts

4-3

given by the user to the Non-resident Monitor or,
if no counts given, the number of .IODEV'ed .DAT
alots calling those handlers.
I/O. buffers are
allowed to overlap core boundaries.

4.3

The amount of free core assigned to the Foreground
job (contents of .SCOM + 25) is added to the current
size of assigned Foreground core to determine the
upper limit of the Foreground job. Pointers to
t~~ first and last registers in Foreground free core
are then stored in .SCOM+2 and .SCOM+3, respectively.

i..

The Loader now exits to the Resident Monitor. The
Resident Monitor prints tS and waits for the user
to type CTRL S, if the Loader is called by the LOAD
c~mmand.
Control then is given to the start address
of the user's main program, which was stored in
.SCOM+6 by the Loader.

BACKGROUND SYSTEM LOADER
Loading of all system programs is done by the System Loader

(.SYSLD), which also performs link loading for the Foreground.
Initiation of the loading cycle is done when the user, in the
Background, types a request to the Non-resident Monitor to load
a system program; e.g., $PIP, $EDIT, etc.
The Non-resident Monitor puts a code number in .SCOM+5 to
tell the System Loader which program to load.

The System Loader

is then loaded into upper core overlaying the Non-resident Monitor .
. SYSLD contains a table which lists the .DAT slots used by
each system program.

Information about the load address, start

address, size and initial block number on the system device for
each system program is available in block

4-4

l~l

(SYSBLK).

To load in a system program in the Background, .SYSLD
performs the following operations:
a.

For each .DAT slot (with non-O contents) required
by a system program, it determines which device
handlers are needed; and, if a library search is
necessary, it brings in the handle.rs from the
file .IOLIB BIN on the system device through .DATB -7.
They are loaded starting immediately above the
top of the Foreground job.

I/O buffers are then assigned core space immediately above the handlers as in the description
in paragraph 4. 2g. ThE~ hardware memory protect
bound is set above the handlers and buffers.

If the load command was $LOAD, $GLOAD, $DDT or
$DDTNS, the Background Link Loader (BFLOAD), a
relocatable file, is loaded starting just above
the new hardware protect bound.

For all other system programs, .SYSLD builds a
short routine just above the hardware protect
bound to bring in the program overlaying the
System Loader.

Finally, . SYSLD exi ts ,to the Resident Moni tor
which establishes the new hardware protect
bound and then passes control to the system
program via the address stored by .SYSLD in
. SCOM+5.

The Loader allows the loading of absolute .LOC programs
prior to loading any relocatable files.

This permits the user

to load programs which may overlay parts of the Resident Monitor.
Mixing of absolute and relocatable .LOC's in the same program
file is not allowed and will be flagged as an error.

The L:::>ader

insures that the relocatable proqrams do not overlay any of the
absolute programs.

4-5

The Foreground Linking Loader is also responsible for loading the system program PIP in the Foreground.

The Foreground

version of PIP exists in the system as the relocatable file
PIP BIN.

It is loaded by typing PIP as a command to the

Non-resident Monitor.
4.4

BACKGROUND LINKING LOADER
Externally, the Background Linking Loader (BFLOAD) looks

nearly the same to the user as the Foreground Linking Loader.
When it has been loaded, it prints the following message on
the Background control teletype:
BGLOA[· V1A
>

The command string processing is identical with that of the
Foreground Linking Loader (see 4.2).
If the Load command was $DDT or $DDTNS, the system program
DDT (a relocatable file) has already been loaded into the top
of core via .DATB -1, prior to reading in the command string.
Once the command string has been accepted, the Loader
will perform the following sequence of operations:
a.

Load all user programs specified in the command
string from .DATB -4. These programs are loaded
from the top of core down. Calls to external
library routines via .GLOBL, common block definitions, and .IODEV requests are saved in the
Loader's symbol table, built from the top of the
Loader upwards in core. Programs containing
ex'ecutable code (which excludes BLOCKDATA
subprograms) are relocated such that they
do not overlap core boundaries.
4-6

4.5

Same action as described in 4.2b, using .DATB -5.

Same action as described in 4.2c, using .DATB -7.

If any I/O handlers must be loaded, the Loader
searches through .IOLIB BIN via .DATB -7. The
handlers are relocated to run in lower core,
that is, as if they were being loaded upwards
in core starting just above the Foreground job.
They may, however, be loaded above the Loader
at this point in time because the Loader is in
the way.

Same action as described in 4.2 e,f,g. Common
blocks are assigned space in upper core; I/O
buffers, in lower core.

The hardware memory protect bound is established
above the I/O handlers and buffers. Common
blocks may go below the hardware protect bound.

If DDT was loaded and a symbol table was requested
(not $DDTNS), the symbol table is compacted to
delete entries not needed by DDT. The Loader
determines where the symbol table should be moved;
and, along with the I/O handlers which were loaded
into upper core, builds a special .EXIT list which
tells the Resident Monitor where to block transfer
each segment. The DDT symbol table may be loaded
bAlow the hardware protect bound.

The Loader then exits to the Resident Monitor,
which performs the block transfers, sets the new
hardware memory protect bound, and transfers
control to DDT (via .SCOM+5) or to the user
program (via .SCOM+6), pausing to print ts and
waiting for the user to type CTRL S if the Load
command was $LOAD.

LOADING XCT FILES
XCT files are overlay programs built by the system program

CHAIN and run by the system program EXECUTE.

Loading of an XCT

file in either the Foreground or the Background is initiated by

4-7

typing EuXXX or EXECUTEuXXX to the Monitor (where XXX is the
file name without the extension XCT).
The Non-resident Monitor, BFKM9, stores the filename (.SIXBT
format)

in .SCOM+l¢7, ll¢ and III for the Foreground or .SCOM+112,

113 and 114 for the Background.

If EXECUTE's .DAT slot requests

the resident system device handler, the Monitor stores "XCS" as
the extension.

If EXECUTE's handler is different from the

resident handler, the Monitor stores the extension "XCT."
The System Loader is then called in, overlaying the Nonresident Monitor in upper core.
4.5.1

EXECUTE in the Foreground

The following operations are carried out when EXECUTE is used
in the Foreground:
a.

EXECUTE's handler, if different from the resident
h~ndler, is loaded immediately above the Monitor.

'rhe System Loader, which must open the XCT file,
checks the extension. If "XCS", meaning EXECUTE's
handler is the resident handler, load the file via
.DAT -7.
If "XCT", load via .DAT -4. Set the
extension to "XCT".

Read the XCT file and check that it was indeed
built to be run in the Foreground of a PDP-9.

Save the upper and lower core limits of the overlay structure and check that it'does not overlay
the Resident Monitor.

Decode the .IODEV bit map in the XCT file. Set
the loading bound immediately above the area of
core to be occupied by the overlay structure and
then load all I/O handlers required by the XCT
file. Also, load another copy of EXECUTE's handler
(the first copy will be overlayed).

4-8

Load in EXECUTE.

S~me

The Loader exits to the Resident Monitor. The
Monitor gives control to EXECUTE, whose start
address is stored in .SCOM+6 by the Loader.

action as described in 4.2g and h.

The following operations are carried out when EXECUTE is used in
the Background:

4.6

EXECUTE's handler, if different from the resident
handler, is loaded inunediately above the Foreground
job.

Same action as described in 4.S.I.b.

Read the XCT file and check that it was built to
be run in the Background of a PDP-9.

Save the lower core limit of the overlay structure
and test, when EXECUTE has been loaded, that they
do not overlap.

Decode the .IODEV bit map in the XCT file and then
load any I/O handlers needed by the file.

Same action as described in 4.2g.

Set the hardware memory protect bound above the
I/O buffers and then load EXECUTE starting above
this bound.

Same action as described in 4.3.e.

ERROR CONDITIONS
The number of different error messages in the Loaders has been

exp2nded in Background/Foreground.
2, Section A2.S.

These are tabulated in Appendix

The error number is passed on to the Resident

4-9

Monitor by a special error .EXIT macro (CAL sequence).
Loader errors are non-recoverable.

After the error message

is printed, the Monitor will automatically be reloaded to
start another job.

4-10

4.7

SYSTEM MEMORY MAPS

Memory Map A
16K
System Bootstrap

The System Bootstrap is loaded at the top of
core via the paper tape reader in HRM format.

4-11

Memory Map B
~~~~~~-r~---System

Bootstrap

8K - - - - - -

• SCaM + l2J --iI"'i--r--r--:r---r-,-4
.SCOM +

Monitor including the mUlti-unit
teletype handler and
the system device handler.

~----Resident

The System Bootstrap automatically loads the Resident
Monitor from the system device into lower core.

4-12

Memory Map C
.SCOM--+-16K
.....----Non-resident Monitor

.SCOM +
.SCOM +

....----Resident Monitor

The Resident Monitor loads the Non-resident Monitor
(via the resident system device handler) into upper
core, overlaying the System Bootstrap.

4-13

Memory Map D
. SCOM---3Io- 16K

. .______ Foreground Linking
Loader (. SYSLD)

. SCaM + 3 --;..+-.L----''---L.._-I

8K - - _ _ _

.SCOM +
.SCOM +

~---------Resident

Monitor

To load a user FOREGROUND program, the Non-resident
Monitor brings in the Foreground Linking Loader
(.SYSLD), overlaying itself.

4-14

Memory Map E
.SCOM--~)o 16K

Foreground Linking Loader
(. SYSLD)
I/O Handlers
Symbol Table

.SCOM +
.SCOM +
.SCOM +
.SCOM +

protect bound
protect bound
Foreground free core
User's I/O Handlers and
I/O Buffers
Foreground user programs

-_---,W-,_~_ _ _ _~Hardware

r-__~__~~~~~~~~~=oftware

Foreground
Job

Resident Monitor

The Foreground Linking Loader first brings in any additional
I/O handlers required for loading. Then it loads the user
program(s), library routines, user I/O handlers and I/O
buffers, and allocates Foreground free core. The software
memory protect bound is established just above the Foreground
job. The hardware memory protect bound, because it can be set
only in increments of lK decimal, will leave some unused space
between it and the Foreground job. The software protect bound
allows this space to be used for dynamic data storage by the
Background job.
For a description of loading of Foreground XCT files, see
Memory Map L.

4-15

Memory Map F
· SCOM----II....
-16K

Non-resident Monitor

.SCOM +
· SCaM +
· SCaM +
.SCOM +
.SCOM +

bound
bound
job

Resident Monitor

o
When the FOREGROUND job becomes I/O bound, control is transferred to the BACKGROUND job. The Resident Monitor loads the Nonresident Monitor (via the resident system device handler) into
upper core.
It then gives control t~ the Keyboard Listener
(within the Non-resident Monitor) to await a BACKGROUND keyboard
command. Memory protect is enabled while the Background job is
running.

4-16

Memory Map G
.SCOM-----I..... 16K
~~_____

.SCOM +

Background System
Loader (. SYSLD)

3------~1~~-~~-L~

.SCOM +
.SCOM +
.SCOM +
.SCOM +
.SCOM +

~-------Hardware
~----Software

protect bound
protect bound

Foreground Job

1----- Res iden t Moni tor

When a BACKGROUND keyboard command requests loading
of a system or user program, the Non-resident Monitor
brings in the System Loader, overlaying itself. Note
that the BACKGROUND System Loader and the FOREGROUND
Linking Loader arc physically the same program.

4-17

Memory Map H
. SCOM------,..... 16K
Background
-System Program
.SCOM + 3-

)10

Background Free Core
.SCOM +

32~

.SCOM +
.SCOM +
.SCOM +
.SCOM +

__----Hardware Protect Bound
~-----Software Protect Bound
~~~~~~~_~__----Background I/O Buffers

Background I/O Handlers
Foreground Job

~------Resident

Monitor

If the BACKGROUND request is for a system program, the
System Loader loads the system program I/O handlers up
from the top of the FOREGROUND job, allocates I/O buffer
space, and loads the system program at the top of core
(overlaying the System Loader). Control is returned to
the Resident Monitor, which sets the memory protect bound
above the buffer space and given control to the system
program.

4-18

Memory Map I
.SCOM
~16K
· SCOM + 3

P/// ~ Background System
V//
rL.....L-L----L--I
Loader (. SYSLD)

· SCOM + 2 - - - - - - - -

~Background

Linking Loader

.SCOM + 32-.-----------.SCOM + 1
· SCaM + 25
.SCOM -I- 31

---

Moni t.or

()

If the BACKGROUND program is a user program*, the
System Loader loads the Linking Loader I/O handlers
up from the top of the FOREGROUND job and loads the
Linking Loader such that the memory protect bound
can be set just below it.,

*Uscr programs may be loaded along with the system
program DDT.

4-19

Memory Map J
.SCOM
.SCOM +

...

ll----~ 16 K

-E,-

Background user Programs
Library Routines

~_Background

User I/O

Handlers
.SCOM + 2

- - - - - - i..... ~-=---;;;:;;';-;::::"';",". ~

Loader's Symbol Table

~ Background

. SCaM + 32 _____~

~Hardware

.SCOM +

Linking Loader

Protect Bound
Prote~t

Bound

. SCaM +
.SCOM +

Foreground Job

The Bl.CKGROUND Linking Loader overlays the System Loader
by loading user programs down from the top of core.
User
I/O handlers, presuming that they cannot fit in core
b(~tweenthe FOREGROUND job and the bottom of the Loader,
are loaded into upper core but relocated to run just above
the FOREGROUND job so that they memory protect bound can
be set above them.
Common blocks and I/O buffers are not
shown in this memory map.

4-20

Memory Map K
.SCOM-----------~~~16K
OII!'----

Background User Programs
and Library routines

- - - - User's Common Blocks
.SCOM +

3--------~I~~~I~~uwy

.SCOM+ 32~
.SCOM + 2 } - _
.SCOM + 31
~

~~-L-..\~~~-'r-'--"-.!-~

.SCOM + l*l
. SCaM + 2 ~r------'~'" I-~..,x-~-......><-.->'_r__"+

~..--Background

handlers

Foreground Job
8K

....-I...E:----Resident

Monitor

The .EXIT from the Linking Loader causes the user program
I/O handlers to be block transferred to their running
position, the memory protect bound to be set just above
the I/O buffer space, and control given to the user program.
if DDT was also loaded, it resides at the top of core, above
the user programs.
Its symbol table, built by the Loader,
is block transferred by the Monitor to start at the software protect bound.
*If DD7 is loadGd, .SCOM + 1 will be set to point at the
start of DDT symbol table.

4-21

Memory Map L
.SCOM

symbol table
.SCOM +
.SCOM +
.SCOM +
.SCOM +

protect bound
protect bound
~ Foreground free core
------~~~~~~~

~~~~~~~EXECUTE

. /0

~~~~~~~

Foreground
Job

Handlers + I/O buffers
including 2nd copy of
EXECUTE's handler
Core occupied by
OverlaY,structure

-=- ~ ~--=-:.

=- J
}

lIs t copy of EXECUTE's
n I / O handler

t---r--r--~-r---r--1

System Loader first loads EXECUTE's I/O handler (if not
the resident handler) in order to read the XCT file.
The
core limits of the overlay structure are read from the file
as well as the request for I/O from its .IODEV bit map.
'rhe requested handlers, including a second copy of EXECUTE's
handler, are loaded above the core area to be occupied by
the overlay structure. Then I/O buffers are created, if
necessary, and EXECUTE is loaded above them.
Finally,
Foreground free core, the software protect bound and the
hardware protect bound are established.

rrhe

4-22

Memox:'y Map M
.SCOM
Core occupied by
Overlay structure
.SCOM +

table

3--------~)o

. SCOM + 2 -~-------~ I-"-''>''''---'--'-->-'~~
.SCOM +

32-------------~·1

.SCOM +

31------~--------~~-~~~~r;'

.SCOM +

25--~---------~.1-~~~~-=~~~

protect bound
Pro.tect Bound
Background I/O handlers
and I/O buffers
Foreground job

8K - - - - - -

Monitor

o
The System Loader loads EXECUTE's I/O handler (if not in
core) in order to read the XCT file.
The core limits of
the overlay structure and tJne I/O requests in the . IODEV
bit map are read from the XCT file.
The user's I/O
handlers and I/O buffers are then laoded above EXECQTE's
handler, and the hardware protect bound is established
above them.
EXECUTE is loaded above the bound and Background free core is set up from the top of EXECUTE to the
bottom of the overlay area.

4-23

SECTION 5
BACKGROUND/FOREGROUND START-UP PROCEDURE

5.1

LOADING THE B/F MONITOR
Before startup procedures can be carried out, the user must

generate a working system

(usin~

supplied with the system.

Refer to Section 8 for .SGEN proce-

.SGEN) from the master tape

dures.
In Disk systems, the Monitor and system programs are
assumed to be on Unit

In DECtape systems, mount the working system tape onto
DECtape unit 8 (i.e.,
1)

and perform the following:

Load appropriate paper tape Bootstrap in the
reader.

Momentarily depress Reader TAPE FEED pushbutton
to clear end-of-tape flag.

Set console address switches as follows:
If you have a -

Set switches to -

16K System

37637

24K System

57637

32K System

1'7637

Press and release in sequence the console I/O
RESET and READ IN switches.

5-1

When loaded, the monitor identifies itself and indicates its
readiness by outputting the following on the Foreground control
Teletype (i.e., norma1iy unit 1)
FKM9 VIA
$

The paper tape bootstraps used to load the Background/Foreground
monitor are identical to those used in the PDP-9 Keyboard Monitor
system.

The bootstrap restart address, however, is different

(i.e.,

.SCOM+11 = register lIla) because the resident Monitor

contains a copy of the bootstrap.
The three examples given in paragraphs 5.2, 5.3 and 5.4
are intended to get the user "on the air".

Note that the symbol

$ is output by the Monitor to indicate that it is ready. to accept

commands, whereas">"and "*" are used by system programs to
denote readiness.
The symbol

® in the text below indicates the typing of

an ALTMODE terminator.
5.2

.IDLE LOADED AS THE FOREGROUND JOB
An Idle job is loaded in the Foreground to allow immediate

use of the Background.

Refer to section 6.3 for a discussion

of .IDLE.
FKM9 V1A
$A ~TA~
DKA~

$GLO D

FGLOAD V1A
>+-IDLE

-4

/The program "IDLE" is on unit
/~ of the system device
/Ca11 the Loader to Load-and-Go
/The Loader is in core
/Load "IDLE BIN".
5-2

When

IDLE is loaded, no indication is given on the Fore-

ground control teletype.

Control passes to the Background

and the Non-resident Monitor is loaded into core.

The Monitor

identifies itself on the Background control teletype as:
/The Monitor is now ready to
/accept background commands.

BKM9 VIA
$

5.3

SINGLE-USER FOCAL LOADED INTO THE FOREGROUND
FKM9 VIA

$A fDT~ -4

/FOCAL is on the "system tape".

$A DT
3
$A TTl 5
$FCORE lfdfJfJ
$GLOAD

/Library input to FOCAL.
/Library output to FOCAL.
/Free core for FOCAL buffer area.
/Call Loader to Load-and-Go.

FGLOAD VIA
>+-FOCAL, FNEW

® /Load FOC.A.L and its library, FNEW

LI?Kfd

FOCAL V3A

/The Loader is in core.

/FOCAL is in core and
lis ready to accept commands.

Once FOCAL is running in the Foreground, the Non-resident
Monitor will be loaded into core as explained in 5.2.
5.4

TWO-USER FOCAL LOADED IN 'rHE FOREGROUND
FKM9 VIA
$A fDTm

LDKm

-4

$A TTl
1
$A DTI
2
$A TT2
3
$A DT2
4
$FCORE 3fJfJfJ
$GLOAD

/FOCAL2 is on the "system tape".
/Teletype for user #1.
/Library In/Out for user #1.
/Teletype for user #2.
/Library In/Out for user #2.
/Assign 14fJfJ (Octal) locations of free
/core for each user.
/Call the Loader to Load-and-Go.

FGLOAD VIA
/The Loadl~r is in core.
;>-<FOCAL2 ,FNEW @ /Load two'-user FOCAL and its
/library, FNEW.
POCAL V3A
/FOCAL is in core and will
*
/identify itself on each user's teletype.
5-3

SEc'rION 6
BACKGROUND/FOREGROUND MONITOR COMMANDS (SYSTEM MACROS)
6.1

INTRODUCTION
The System MACROS unique to the Background/Foreground

Monitor are listed and described briefly in Table 6-1.

The

Monitor Macros listed are available in addition to the Macros
provided in the Advanced Keyboard Monitor System for use in
programs that are to be run in the Background/Foreground environment.

Detailed descriptions of the Macros are given in

the remainder of this Section.

'rABLE 6-1
Background/Foreground System Macros
Name

Purpose

.REALR

Real time transfer of data from I/O device to
line buffer (real-time READ).

.REALW

Real time transfer of data from line buffer to
I/O device (real-time WRITE) .

. IDLE

Allows FOREGROUND job to indicate that control
can be given to lower levels of the FOREGROUND
job or to the BACKGROUND job until completion
of any FOREGROUND real-time transfer or clock
interval.

.IDLEC

Allows FOREGROUND Mainstream to give control
to BACKGROUND job with FOREGROUND continuinq
ufter the .IDLEC on completion of any FOREGROUND
rCul-time transfer or clock interval.

.'rIMER

Calls and uses real-time clock and allows
priority level to be established.

.RLXIT

Accomplishes the exit from all real-time
subroutines that were entered via .REALR,
.REALW, .TIMER or real-time CTRL pl requests.

See Section 3.7.

6-1

6.2

.REALR
FORM:

'. RE,ALR A, M, L, W, ADDR, P

VARlALLES:

A = .DAT slot number (octal radix)

f1
1

M = Data Mode
1

{

lOPS binary
Image binary
lOPS ASCII
Image Alphanumeric
Dump Mode

15-bLt buffer address

Line buffer word count (decimal radix) I
including the two-word header

(octal radix)

ADDR = IS-bit address of closed subroutine that
is given control when the request made by
the .REALR is completed.
P

API priority level at which to go to ADDR
P

Priority Level

fJ
4
5

Mainstream
Level of . REALR
API software level 5
API software level 6
API software level 7

6
7

EXPANSION:

LOC
LOC+l
LOC+2
LOC+3
LOC+4

CAL+lfJfJfJ~+M6-8+A9-17

IfJ
L

.DEC
-W
.OCT
ADDR+PO-2

/Decimal Radix
/Octal Radix

IData modes 5, 6 and 7 are passed to all I/O handlers.
2The subroutine specified by a .REALR, .REALW, .TIMER or realtime CTRL P should not be used at more than one priority level.
The subroutine is entered via a JMS and thus cannot be protected
against re-entry.

6-2

DESCRIPTION: The .REALR command is used to transfer
the next line of data from the device assigned to .DAT
slot A to the line buffer in the user's program.
In
this operation, M defines the modes of the data to be
transferred, L is the address of the line buffer, W is
the number of words in the line buffer (including the
two-word header), and ADDR is the address of a closed
subroutine which should be constructed as shown in the
following example.
EXAMPLE 1:
ADDR

STRUCTURE OF A REAL-TIME SUBROUTINE

/Entry point

DAC

S AVE AC

/Eave AC
/Any system Macro may
/be issued at this point.

6.3

LAC

SAVEAC

/Restore AC

.RLXIT

ADDR

/Return to interrupted
/point via Monitor CAL

.REALW
FORM:

.REALW A, M, L, W, ADDR, P

VARIABLES:

A = .DAT slot number (octal radix)

{

~ =

IOPS binary
1 = Image bina-i:y
2 = IOPS ASCII
3 = Image Alphanumeric
4 = Dump Mode

Ml=

Data Mode

IS-bit Line buffer address (octal radix).

Line buffer word count (decimal radix),
fucluding the two-word header

ADD~= IS-bit address of closed subroutine that

is given control when the request made by
the . REALvv is completed.

1 Da ta modes 5, 6 and 7 are passE~d to all I/O handlers.
2See footnote 2, page 6-2.

6-3

API priority level at which to go to ADDR
priority Level

Mainstream
Level of .REALW
API software level 5
API software level 6
API software level 7

4
5
6
7

EXPANSION:

LOC
LOC+l
LOC+2
LOC+3
LOC+4

CAL+l~~~~+M6-B+A9-17

L
.DEC
"'W
.OCT
ADDR+Po- 2

/Decimal Radix
/Octal Radix

DESCRIPTION: The .REALW command is used to transfer the
next line of data from the line buffer in the user's
program to the device assigned to .DAT slot A.
In this
operation, M defines the mode of the data to be transferred, L is the address of the line buffer, W is the count
of the number of words in the line buffer (including the
two-word header), and ADDR is the address of a closed subroutine which should be constructed as shown in EXAMPLE 1
above.
6.4

. IDLE
FORM:

. IDLE

EXPANSION:

LOC
LOC+l

CAL

DESCRIPTION: The FOREGROUND job in a Background/Foreground
environment can indicate that it wishes to relinquish
control to lower levels of the FOREGROUND job or to the
BACKGROUND job by executing this command. This is useful
when the FOREGROUND job is waiting for the completion of
real-time I/O from anyone of a number of I/O requests
that it has initiated or for completion of .TlMER requests.
The .IDLE is the logical end of the current level's processing; that is, control never returns to LOC+2.
If the .IDLE
is issued at a FOREGROUND API software level, it effects a
debreak (DBR) from that level so that pending real-time

6-4

routines at that level will not be executed until the
level is requested again. If the .IDLE is issued at
FOREGROUND Mainstream, control goes to the BACKGROUND
job.
If the .IDLE is issued at BACKGROUND Mainstream,
control is returned to the .IDLE CAL.
6.5

.IDLEC
FORM:

.IDLEC

EXPANSION:

LOC
LOC+I

CAL+I~J~JiY

DESCRIPTION: Identical to .IDLE except when issued at
the FOREGROUND Mainstream level. In this case, control
goes to the BACKGROUND job, and LOC+2 is saved as the
FOREGROUND Mainstream return pointer. The next time
control returns to FOREGROUND (at any priority level),
FOREGROUND Mainstream processing will resume at LOC+2
when Mainstream becomes the highest active FOREGROUND
level.
6.6

.TIMER
FORM:

.TIMER N, ADDR, P

VARIABLES:

~ = Number of clock increments

(decimal radix)

ADDlf= IS-bit add.ress of closed real-time subroutine to handle interrupt at end of
interval
P

API priority level at which to go to ADDR

lTo transfer control to subroutine ADDR at priority level P
immediately, N should be set equal to zero.
2The subroutine specified should not be used at more than
one priority level. The subroutine is entered via a JMS
and thus cannot be protected against re-entry.

6-5

priority Level

Mainstream
Level of .TIMER
API software level 5
API software level 6
API software level 7

6
7
EXPANSION:

LOC
LOC+I
LOC+2
LOC+3

CALI

14
ADDR+Po-2
.DEC
-N

/Decimal Radix

DESCRIPTION:
.TIMER is used to set the real-time clock
to N increments and to start it.
Each clock increment
represents 1/60s for 60 Hz systems and 1/50s for 50 Hz
systemi. When the Monitor services the clock interrupt,
it passes con"trol to location ADDR+l with the priority
level set to P.
The coding at ADDR should be in closed
subroutine fo:rm, as in EXAMPLE 1.
6.7

.RLXI':.'
FORM:

.RLXIT ADDR

VARIABLES:

ADDR = l3-bit entry point address of the
real-time subroutine from which an
exit is to be made.

EXPANSION:

LOC
LOC+I

CAL

ADDR

DESCRIPTION:
.RLXIT is used to exit from all real-time
subroutines that were entered via .REALR, . REALW , .TIMER
or real-time CTRL P requests.
The instruction just
preceding the .RLXIT call should restore the AC with
the value of the AC on entrance to this subroutine.
.RLXIT
will restore the link from bit ~ of the contents of ADDR .
. RLXIT protects against re-entrance to BACKGROUND or FOREGROUND Mainstream real-time subroutines. When the contents
of ADDR is non-zero, the subroutine is assumed active;
.RLXIT sets the contents of ADDR to ~, thus making it availlWhen bit 8 of CAI~ is set to I, an abort • TIMER is effected.
All intervals having the same address and priority level (LOC+2)
will be aborted.

6-6

able again.
NOTE:
Real-time subroutines should initially
hav.e their entry point register set to fO; and restart
-procedures, enteredvla CTRL P or after CTRL T, shOUTd
reset all entry pOlnts to ~.
6.8

MAINSTREAM REAL-TIME SUBROUTINES
Mainstream real-time subroutines in the Foreground are

not equivalent to those in the Background due to the manner
in which I/O busy situations are handled.

If the Background

becomes I/O busy, the Monitor "sits on" the Background CAL
instruction (while Background is in control) until it can be
processed.

Therefore, Background Mainstream real-time routines

can be executed despite the fact that Background Mainstream
is I/O busy.

If Foreground Mainstream is I/O busy, Foreground

Mainstream real-time routines cannot be executed until the busy
situation is terminated.

This is due to the fact that control

is given to the Background whenever Foreground Mainstream
becomes I/O busy_

The device handler responsible for the busy

situation is rememberod in the Foreground Mainstream busy flag.
Mainstream real-time routines cannot then be run because they
too could become busy.
This situation can be avoided either by usinq .REALR or
. REALW in conjunction with . IDLE or . IDLEC, or by usinq . v-7AITR
to prevent Foreground Mainstream from becoming I/O bound.

6-7

SECTION 7
WRITING DEVICE HANDLERS FOR THE BACKGROUND/FOREGROUND
MONITOR SYSTEM

7.1

INTRODUCTION
Writing a handler which will run in the Background/Foreground

Monitor environment requires adherence to certain established
conventions which differ from those in the Keyboard Monitor environment.

The CAL handler in the Monitor has been implemented

to do as @uch of the function processing as possible.

In giving

control to the I/O handler, the CAL handler will have set up
registers in the I/O handler with all pertinent information (arguments) of the CAL in the most accessible state, and will then
transfer control to the appropriate function processor via the
JMP table in the I/O handler which begins at word 208.

There

are three types of I/O device handlers that one may wish to develop
to operate under the Background/Foreground Monitor System:
1.

Single user --- This handler can be used by either
the Foreground job or the Background job but not
both during the same core load; that is, it is
dedicated to one job and the Monitor System will
not permit the other job to be connected to it.

Sequential Multi-user --- This handler can be connected to both the Foreground and the Background
job and they both can utilize it on a sequential,
first come-first served basis.

Multi-user --- This handler can be connected to
both the Foreground and the Backqround jobs with
the Foreground job having priority on usage.
If
the Background job is using the handler and Foreground requires it; the Background I/O will be
deferred until the Foreground I/O has been completed.

This section will be primarily devoted to describing the
development of single-user handlers.

After having done this,

it will show the transition fro:m single use to sequential multiuse.

7-1

I/O handler type 3 (Multi-user) is too involved to be
presented without example listings

(such as our Multi-user

DECtape handler) and personal consultation regarding the
philosophies of the Background/Foreground Monitor System.
Consultatio~

is available to customers whose applications

require type 3 handlers.
7.2

FORMAT OF DEVICE HANDLER'S CAL PROCESSOR
The first 37 (octal) words of the I/O handler must have

the format described in the following pages.

An assembly

listing of the Background/Foreground line printer handler
(LPA) is appended to this section for reference.
WORD~:

JMS

SWAP

/SWAP is in the I/O handler

The SWAP subroutine must execute WORDS which restores the
state of the program interrupt and DBK from level

of the API.

The presence of this routine becomes functionally necessary
for type 3 (Multi-user) handlers to accomplish swapping from
Background to Foreground usage.

The I/O device

independ~nce

of the system requires that all handlers look alike to the
outside world (namely, the CAL handler).
WORD 1:

Foreground Busy Register

must be assembled
with ~ contents

~=Not Busy
Non~=Busy (Current

.DAT slot number, 18 bits
if negative)

WORD

Background Busy Register
~=Not

Non~=Busy

must be assembled with
~ contents

Busy
(Current .DAT slot number, 18 bits
if negative)
7-2

The CAL handler checks the validity of the .DAT slot
number for this job (Foreground or Background), checking for
its existence, whether or not a device has been assigned to
it and if the appropriate handler was loaded.
The CAL handler then checks the appropriate busy register
and proceeds as follows:
1)

If the flag indicates that the handler is
already busy, the job becomes I/O bound at
this level.

If the flag indicates not busy, it is set
to busy and the CAL handler processes the
function and passes the request on to the
device handler.

Note that .WAIT's and .WAITR's are completely processed
by the CAL handler and are not passed on to the I/O handler
If the corresponding flag indicates:
1)

BUSY
a)

For .WAIT in the Foreground, control
is given to a lower Foreground level
or the Background.

For .WAIT in the Background, hang on
the CAL.

For .WAITR in either the Background or
Foreground, control goes to the address
in LOC+2 (which must be above the hardware memory protect bound if in the
Background) .

NOT BUSY - Fall through.

WORD 3:

Foreground .CLOSE register -- must be assembled
with fJ contents
!J=.CLOSE not in progress
NONfJ=.CLOSE in progress

7-3

WORD 4:

Background .CLOSE register --- must be assembled
with ~ contents
~=.CLOSE not in progress
Non~=.CLOSE in progress

WORD

ION or IOF (state of PIC on INTERRUPT or CAL entries).

WORD

Same as WORD 5 on CAL entries; DBR on INTERRUPT
entries.

WORD~:

WORD

l~:

Return pointer. The CAL handler places the
address of CALXIT in this register.
JMP FUNC

After checking the validity of function and subfunction
codes, the CAL handler places a JMP to the appropriate entry
in the function JMP table (words 2~-32) of the I/O handler
in this register.
WORD 11:

User CAL in progress.
register.

The CAL handler sets this

~=Foreground

l=Background
WORD 12:

.DAT slot number (IS-bits if negative).
CAL handler sets this register.

The

WORD 13:

Unit number for Multi-unit devices in Bits ~-2,
with bits 3-17 containing the address of the
CAL. The CAL handler sets this register.

lWhen a hardware interrupt occurs to this I/O device handler, the
interrupt processor must:
a)
Save the state of the program interrupt in Word 5
b) Place a DBR in Word 6
c) and place the interrupted program counter (with link,
extend mode and memory protect bits) in Word 7.

7-4

The CAL handler makes a general check for validity on:
a)
b)
c)
d)
e)
f)
g)

File type
Data Mode
MAGtape subfunction code
Transfer directions
.OPER subfunction code
All addresses
Word counts

and will pass on what appears to be legitimate values . . Each
handler must then make its own validity determination with
respect to the device it controls.
will always accept data modes

For example, the CAL handler

through 7; however, the device

handler may only accept a subset of these.

The contents of words Word 14 through Word 17 vary with
the function being processed.

l\.dj acent to what will appear

in each of these words is the limits on the values that will
be accepted and passed on by the CAL handler.

WORD 14:

.INIT --- File type

~=input

l=output
.READ, .REALR
.WRITE, .REALW - Data Mode 2

.MTAPE
.TRAN
.OPER

binary
l=imaqe binary
2=IOPS ASCII
3=Imaqe ALPHA
4=DUMP
5=DUMP ALPHA
6=are passed on
7=by the CAL handler

~=IOPS

--MAGtape function
--Transfer direction
--Subfunction code

7-5

(~-178)
(~-3

(1-3 )

WORD 15:

.INIT --- User restart address plus code bits (~-2)
.READ, .REALR
.WRITE, .REALW --- Line buffer address (checked
for memory violation on software protect
bound (SCOM+3l) if Background job .
. DLETE , .RENAM
.FSTAT, .ENTER, .SEEK --- Address of Directory
entry block (checked for memory violation
on .SCOM+31 if Background job) .
• 'rRAN --- Core starting address

(checked for
memory violation on .SCOM+31 if Background
job .

WORD 16:

. INIT --- Address of Register which is to have
standard buffer size placed in it (checked
for memory violation on .SCOM+31 if Background job) .
. TRAN, . READ , .REALR -- Line buffer word count
(from CAL ARG. LIST). Counts are checked
for core fit and negative value if Background job .
. WRITE, .REALW --- Line buffer word count (from
line buffer word pair ct., except for
dump mode and Mode 5 which use counts
from CAL argument list.)
Counts are
checked for core fit and negative value
if Background job.

WORD 17:

.TRAN --- Device address tBlock number)
.FSTAT --- Address of register which will have
the device code put in bits ~-2, (checked
for memory violation on . . SCOM+31 if
Background job) .
. REALR, .REALW --- Address to give control to on
completion of I/O request and priority
level in bi ts ~-2 1 , (checked for memory
violation on .SCOM+32, the hardware protect
bound, if Backqround job).

lIf--it is a Background CAL, bits ~-2 of this register will always
contain ~, which indicates Background Mainstream.
If it is a
Foreground CAL and there is no API, bits ~-2 contain 1, the Foreground Mainstream code.
7-6

Function JMP Table
Ignored functions, functions that do not issue lOT's at the
CAL level, and error functions must set up to have the Foreground or Background busy flag

(Words 1 a~d 2, respectively)

cleared during the protected exit routine (which begins at
LPTIO in the line printer handler).

WORD 32:

JMP INIT
/Function 1
/Function 2
JMP OPER
JMP SEEK
/Punction 3
/Punction 4
JMP ENTER
/Function 5
JMP CLEAR
/punction 6
JMP CLOSE
JMP MTAPE
/Function 7
JMP READ ( .REALR) /Function 1.0
JMP WRITE ( . REALW) /Punction 11
NOP
/.WAIT or .WAITR never get to
I/O handler
/Punction 13
JMP TRAN

WORD 33:

WORD 34:

SUBRF

WORD
WORD
WORD
WORD
WORD
WORD
WORD
WORD
WORD
WORD

2~:

21:
22:
23:
24:
25:
26:
27:
30:
31:

/Storaqe for .SCOM+35, the "in
an interrupt service" flag.
/Stop FGRD I/O subroutine

When the Foreground job terminates (.EXI1', tc, terminal error, etc.)
this routine in every Foreground device is called at Mainstream
level to effect the controlled shutting down of the device (see 7.4).
WORD 35:

/Stop BGRD I/O subroutine

SUBRF

For single user device handlers (devices that
cannot be shared by Foreground and Background) ,
the same subroutine can be used for FGRD and
BGRD STOP I/O.
WORD 36:

/Handler I.D. code

This word has other values (Non-0) for devices
that require special consideration from the CAL
handler.

7-7

7.2.1

. SETUP

On the first (and only on the first)

.INIT to a device handler,

the device handler must call .SETUP to connect the device handler's
interrupt service routine to the appropriate API channel register
or program interrupt skip chain entries.

The address of .SETUP

can be found in .SCOM+55 (155 ),
8
Calling sequence:
LAC *
DAC
JMS*
LSDF
LPINT

(. SCOM+55
LPTEMP
LPTEMP
/SKIP lOT
/ADDRESS OF INTERRUPT SERVICE

If this is not done, the first hardware interrupt for this device
will be deemed an illegal interrupt and processed accordingly.

It is imperative that all lOT's that initiate hardware operations be executed during protected (API level

IOF) exit from

the handler to assure that the exit takes place prior to the
hardware operation completing and causing re-entry to the handler
at the interrupt level for servicing.
CAL function requests that require more than one hardware operation should cause the 2nd throuqh Nth operations to be initiated
at the interrupt level durinq protected exit.

7-8

A handler should

not cause sitting on a CAL until the entire function is completed because this prevents opt.imum usage of central processor
time for the duration of the function.

The user cannot do

other things while the hardware operations proceed.
7.2.3

.OPER Functions

.OPER functions

(.FSTAT, .RENAM and .DLETE) are unique in

that they return information in the AC.

For device handlers

that wish to utilize this function, the method is as follows:
On completion of .OPER operation, the interrupt
service level of the handler sets the appropriate
close register (Word 3 if Poreground, Word 4 if
Background) to:
l=File not present
INFORMATION+l=File present (where information
is the device block number).
The information must not = -1
As at the completion of other I/O requests, it sets up to have
the appropriate busy flag (Word 1 if Foreground, Word 2 if Background) cleared during protected exit.
7.3

FORMAT OF DEVICE HANDLER'S INTERRUPT PROCESSOR
Figure 7-1 contains a detailed flow chart of the interrupt

service routine of a single-user handler.

This is the actual

flow chart of the LPA. handler whose listing is appended to
this section for reference.

7-9

fnterrupt Processor of Device
Handler in BACKGROUND/FOREGROUND
MONITOR Environment
LPINT
Save AC, PC, L, XM, MP
in WORD7 of handler.
Save status of PIC in WORD5.

len-tered WI. th-memory - -I
Iprotect disabled and
I
.- ...... "', at hardware level (API I
I~r_ PIcl...?~~e~ice_ _ _ .l

[Jfave contents of .SCOM+35
in WORD33 of handler
_ _ _ _ _ _ _ _ _ _- L_ _ _ _ _ _ _ _ _ _ _ _ _ _

non ~ to .SCOM+35
(on exit, .SCOM+35 is
returned to its saved state)

I When -:-SCOM+35 i-; no~"".01
lat least one interruptr
.- .- L:>ervic=- i~ in ..Erogre~l
Wh;n -locatio;-~ i s -;'on ~ I
lat least one interrupt
I
I~ervic-=- is .....in .J?rogr-=ss
I

Set location
to ~

")--L--~ ~

Clear
STOP I/O
Switch

Clear flag, enable PIC,
DBR to WORD6 of handler~------~

N
>--------:~

Process
Interrupt
Set up to issue
next lOT in protected (API and
~----~PlC) exit routine.

LPEMPT
L. _ _

Set up to have BGRD or FGRD
flag cleared during
protected exit routine.

~ busy

Figure 7-1

IWORD I 1 Ofhandlerl
lindicates BGRD orl
--I FGRD ownership ofl
1.2/~ reque.:..t ~ _ ..J

Interrupt Service Routine, Flow Chart
7-10

Ithi; is -the -commo~1
Iprotected exit fori
,interrupt and CAL I
I~ntr~s ______ ,

LPNOR
Check for device ready
prior to initiating I/O

LPTIO
FEh"Ts-was-an - ,
IRaise to API level ~, IOF
NOTE:
linterrupt
I
The addrese of
Iservice entry I
CALL4 is in
---:::;..-- --,./"
.SCOM+S4 (154 8 )
./"
CALL4 initiates
JMS CALL
an API (or
WORD7
pseudo API)
WORD33
level 4 interrupt with the
level 4 interrupt
processor
LPT.6
controlling
r----------------~------------~
restore .SCOM+3S from
BGRD to FGRD
WORD33 of handler
transitions
and realtime requests.
Clear BGRD and/or FGRD busy
flag as previously set up.

LPIOT
~l
execute setup lOT (IOF if
completE!d)

! J
Irestore AC DBK from level

execute WORDS which is the
exit status of PIC

jcxecute WORDG (DBR i f interrupt entry, same as WORDS if
CAL entry)

exit

Figure 7-1

(Cont.)
7-11

LPT3l
Raise
IOF
NOTE:
The address of
IOBUSY is in
.SCOM+52 (152 8 ).
If the FGRD job
became I/O bound
on this handler.,
IOBUSY will prime
the Monitor to
continue the
FGRD job on the
busy CAL.

/' /

ION
DBK from API level

(Check if-thi;-I
·Idevice involvedl
......1 it; .1/0. busy
I
I~F!:..u~t2:..0n ___ 1

LPNOR

Raise to API level
IOF

ICall real=- --I

I time processor 1
I with level/

I subroutine

I,
I""",

La~d~e~ J-~ AC .J

NOTE:
The address of
REALTP is in
.SCOM+Sl (ISla).
REALTP pr ilfles
the Monitor to
honor real-time
requests.

ION
DBK from API level

ITO determine whether the completed operation is real-time:
a)

WORDl~
WORD 3 ~

and WORDl7 must be

must contain a JMP to WORD27
(. WRI'rE or . REALW) .

(READ or .REALR) or

non-~.

Figure 7-1

7-12

(Cont.)

Please note that interrupt service routines (the
coda beginning at LPINT in the LPA. handler) must be set up
to operate with or without API.
7.4
7.4.1

SYSTEM ANNOUNCEMENTS
Errors

All device handler error messages should be terminal; that is,
should terminate the operation of user programs.

After the

printing of the error message, the user has the option of
typing CTRL P (to restart his program at the CTRL P restart
address), CTRL T (to return to DDT), CTRL Q (to take a dump
of memory), or CTRL C (to return to the Monitor to load
another job).
Device handlers that wish to set up an error condition should
use the following coding sequence:
(. SCOM+66
LAC*
TEMP
DAC
LAC
( 4~~2~~
ISA
IOF
CODE
LAW
JMS*
TEMP
AUXARG XX
DBK
ION
/CLEAR BUSY FLAG (WORD 1 or WORD 2)
/EXIT HANDLER VIA PROTECTED EXIT.

/POINTER'TO ERRORQ
/SUBROUTINE.
/RAISE TO API
/IJEVEL ~.
/SEE BELOW.
/CALL ERRORQ.
/AUXILIARY ARGUMENT.
/RETURN HERE.

The first argument, given in the AC to ERRORQ, may be loaded
either by LAW code or by LAC code in the following format:

7-13

Code
Bits ~-5 are ignored
Bit 6=1 means terminal error
Bit 7=1 means Background error l
Bit 8=1 means Foreqround error l
Bits 9-17 is a 3-diqit error code
The auxiliary argument, following the JMS to ERRORQ, will be
printed in the error message as a 6-digit octal number.

The

error message will be printed in the form:
.ERR NNN XXXXXX
where NNN = the 3-digit error code

xxxxxx = the 6-digit auxiliary information
The actual printing of the error message and processing of
the error will be done only after all interrupt processing
has ceased and when control is no longer in the CAL handler.
7.4.2

Recovery from I/O Device Not Ready Condition

The Background/Foreground monitor system is designed to handle
simultaneously one not-ready condition per job.

This is a

limitation but a reasonable one based on Keyboard Monitor
(single-user) experience.

I/O handlers that can encounter and detect not-ready conditions
must adhere to the following ground rules in their announcement
of the non-terminal error and in their continuation once the
condition has been corrected.
IBits 7 and ·8 may both be set if the error applies to both the
Foreground and the Background jobs.
7-14

Since all 1/0 in B/F handlers must be initiated in the common,
protected exit routine of the handler (the code beginning at
LPNOR in the line printer example), it is there and only there
where not-ready conditions should be checked and handled. 1
Prior to executing the desired IOT, check for not-ready with
the code at LPNOR which is as follows:
LPNOR

IDO WHATEVER IS NECESSARY
ITO DETERM,INE WHETHER
IDEVICE (UNIT) IS READY.
JMP LPRDY
IDEVICE READY.
IWITH THE DEVICE (UNIT) NOT READY IT
lIS NOW NECESSARY TO DEFER THE
IDESlRED lOT, ANNOUNCE THE NONITERMINAL ERROR, AND EXIT FROM. THE
IHANDLER SET UP TO CONTINUE WHEN
ItR IS TYPED O~ THE USEP'S CONTROL
ITELETYPE.
LPIOT
!Sl\VE DESIRED lOT.
LAC
LPIOTB
DAC
I
LAC
(IOF
IEXECUTE IOF IN
DAC
LPIOT
IPLACE OF lOT.
JMS
LPMSG
IINITIATE NOT READY MSG.
LPRDY

Where the code at LPMSG is as follows:
ISUBROUTINE TO CALL A ROUTINE IN THE RESIDENT
IMONITOR TO INITIATE A NOT READY MESSAGE.
ICALLING SEQUENCE:
I
JMS LPMSG
I
RETURN WITH LPCTLR NON-~ IF
I
REQUEST HONORED, OTHERWISE,
I
LPCTLR IS SET TO ~ AND A
I
TERMINAL ERROR WILL RESULT

IThe exception to this is when a handler can only determine not
ready at the interrupt level; that is, after it has issued the
desired lOT and an error flag results.

7-lS

LPMSG

LPARGl
LPARG3

/DETERMINE WHICH JOB (FGRD OR BGRD)
/IS CURRENTLY MANIPULATING THTS DEVICE.
LAC
LPA.+ll
/~=FGRD,l=BGRD
DAC
LPARGl
LAC
LPCTLR
/EXIT IF MESSAGE
SSA!CMA
/ALREADY REQUESTED
JMP*
LPMSG
/FOR THIS DEVICE.
DAC
LPCTLR
/SETtR FLAG.
LAC
UNITNO
/UNIT NUMBER (BITS
DAC
LPARG3
/~-2) IF APPLICABLE.
LAC *
(.SCOM+64
/POINTER TO tR
DAC
LPTMPl
/QUEUER IN MONITOR.
LAC
(4~~2~~
/RAISE TO API
ISA
/LEVEL ~ AND
IOF
/TURN OFF PIC.
JMS*
LPTMPl
/GO TO tR QUEUER.
XX
/~=FGRD, l=BGRD •
. ASCII
/LP/
/DEVICE NAME
.LOC
.-1
~
/UNIT NUMBER (BITS ~-2) IF APPLICABLE
LPFRA + 2~~~~~ /FGRDtR SUB AND DEVICE'S API LEVEL
LPFRA + 2~~~~~ /BGRDtR SUB AND DEVICE'S API LEVEL
DSM
LPCTLR /REQUEST NOT HONORED-TERMINAL ERROR.
ION
/PIC ON (RETURN HERE IF HONORED).
DBK
/DEBREAK FROM LV~
JMP*
LPMSG

Where the code at LPFRA is as follows:
/SUBROUTINE ENTERED AT API LEVEL 2, PIC OFF.
/WHEN tR IS INPUT FROM KEYBOARD, EVEN IF DEVICE IS
/ONLY CONNECTED TO PIC, AN API HARDWARE
/LEVEL (~,1,2,OR 3) MUST HAVE BEEN SPECIFIED.
LPFRA
~
DSM
LPCTLR
/CLEAR tP FLAG
/DO WHATEVER IS NECESSARY
/TO DETERMINE WHETHER DEVICE (UNIT)
/IS READY
/IF STILL NOT READY, CALL LPMSG
/TO CAUSE NOT READY MESSAGE TO BE
/OUTPUT AGAIN.
LPMSG
JMS
JMP
LPFOUT
/BYPASS lOT.
LPIOAC
LAC
/AC FOR lOT IF APPLICABLE.
LPIOTB
XX
/DEFERRED lOT.
LPFOUT
ION
/PIC ON.
DBR
/DEBREAK FROM LEVEL ~.
JMP*
LPFRA
/'rTfF. CONTROL R(fR) IN PROGRESS FLAG
/MUS'.r TNI'l'IALLY BE CLEARED IN THE
/S'J'OP I/O ROUTINE.
r,PC'rLH
ftJ
/tR FLAG
7-16

7.5

STOP I/O TECHNIQUE
In the Background/Foreground Monitor environment, it is

necessary to have some orderly means of stopping I/O
in progress.

(.EXIT, tc, terminal error,

When a job terminates

('te.), Ul(\ Monitor SYf:;tem must

assurc~

is rdlUt down before!

t:h(~

from

cor~.

i.t

rcmovns

that is

that all I/O for that job

associatQd device handlers

This is accomplished via the following method:

Word 34 of every device handler points to the
Foreground STOP I/O subroutine which is
internal to the handler.

Word 35 of every device handler points to the
Background STOP I/O subroutine which for
single-user handlers can be the same as the
Foreground STOP I/O routine.

When a job terminates, the Monitor calls the
appropriate STOP I/O subroutine at Mainstream
level which actually accomplishes the orderly
shut down of I/O.

For devices that can sf:op I/O hardwarewise,
via an lOT, this plus steps 4, 5, 6, and 9
must be done.

For devices that cannot stop I/O hardwarewise via an lOT,
the following procedure can be used:

Raise to level fJ of the API and turn off the
program interrupt to protect against getting
interrupted in mid-decision.

Check the fR flag.
If it is set, clear the
software flag that will be tested in Step 8
and bypass Step 3.
This is done because no
I/O is under way if this handler is waiting
on a tRw

7-17

Check the appropriate busy register (WORDl
WORD2).
If it is not set, no I/O is in
progress; therefore, we do not have to wait
tor its completion.
If it is set, set a
software flag that will be tested in Step 8.
o~

Clear the appropriate busy register (WORDl
or WORD2).

Clear the appropriate .CLOSE register (WORD3
or WORD 4 ) •

Clear the tR flag (see Section 7.4.2).

Debreak (DBR) from API level ~ and turn on
the program interrupt to allow servicing of
hardware flags that may have or will occur.

If the appropriate busy register had been
set, sit in a tight loop testing the
software flag that was set in Step 3 above,
I.E.

LAC
SSA
JMP

FLAG

.-2

FLAG is the STOP I/O switch that must be
cleared (SET=~) by the interrupt service
routine on all interrupts that are final.
Final means that no other flags will occur
without more I/O being initiated via an lOT.
The interrupt service routine must also
make a decision whether or not to initiate
more I/O. When the appropriate busy register (WORDl or WORD2) has been cleared,
(Step 4) this should indicate that no new
I/O should be started.
(See the flow chart
in Section 7.3).
9)

Exit from the STOP I/O subroutine.

7-18

7.6

SEQUENTIAL MULTI-USER DEVICE HANDLER
To accomplish the transition from a single-user device

handler to a sequential multi-user device handler, the following procedures must be adhered to:
a)

The device handler mus"t be the "A" version;
that is, LPA., MTA., etc. as the Background/
Foreground Moni tor Sys"tem will only allow "A"
versions to be connected to both jobs simultaneously. Also, this shareability must be
specified to the B/F system"at generation
time.

The SWAP subroutine (pointed to by WORD~ of
the handler) must set both busy registers
(WORDI and WORD2) to prevent the Foreground
job from forcing itself in before the Background job has completed its operation.
This is in addition to and prior to its
normal duties as outlined in 7.2.

There must be two unique stop I/O subroutines,
one for Foreground (pointed to by WORD34) and
one for Background (pointed to by WORD35) .
Before executing the STOP I/O procedures, both
subroutines must first determine if the I/O
belongs to their respective job. This is done
by testing WORDII, (~=Foreground I/O, I=Background I/O).
They should do nothing if the
other job is in control.
In Step 2 of the stop I/O Routine, if the tR
flag is set, the I/O busy routine in the Moniter (pointed to by .SCOM+52) must be called in
CUHC the Foreground job is I/O bound on this
d(~vice .

Bacause the SWAP ~jubrou"tine sets both busy
registc~rs
(WORDI and WORD2), the CLEAR BUSY
FLAG routine that sets up to have the flags
cleared during protected e~it from the device
handler must always set up to have both flags
cleared. The STOP I/O subroutines should also
clear both busy registers.

7-19

7.6.1

.WAITR

When a sequential multi-user device handler is being used by
the Background job, the Foreground job will become I/O bound
if it attempts to use the same handler.
The .WAITR monitor function affords both the Foreground job
and the Background job a means of determining that the handler
is available before requesting I/O from and to it.

This

feature is only useful when the job has other things which
can be performed while it is waiting for the handler to free
up.
7.7

DEVICE HANDLER LISTING

A listing of the Background/Foreground line printer device
handler (LPA) is given on pages 7-21 through 7-34 of this
section.

7-2Q

PAGE

D A
~

.., •

70 65 0 1
706502

706566
706526
706546
706601

A·
A
A
A

706602
706606

A
A

706626

0000133

., .•

,TITLE LPA.
ED IT ~4 , .•. 2 DEC 69

ILPA.---8AC~GROUND/FOREGROUND MONITOR SYSTEM.
ILPA.=LINE PRINTER (647) HANDLER,
ICALLING SEQuENCE:
ICAL+.OAT SLOT (9-17)
IFUNCTION
IN ARGUMENTS, WHERE N IS A FUNCTION OF FUNCTION.
INORMAL RETURN
LSDF=7e6501
ISKIP ON DONE FLAG -CONNECTED TO INTERRUPT
LPCB=7e6502
ICLEAR DONE FLAG, CLEAR PRINTER BUFFER,
ISET aONE FLAG
ILOAD PR!NT[R RUFFER 1 CHAR (Ae 12-17)
LPL1=706566
ILOAD PRINTER RUFFER 2 CHAR (AC 6-11. 12-17)
LPL2=706526
ILOAD PRINTER BUFFER 3 CHAR (AC 0-5.6-11,12-8)
LPLD=706546
ISKIP ON ERROR FLAG -NOT CONNECTED TO
LSEF=706601
IINTERRUPT
ICLEAR DONE FLAG
LPCF=706602
ICLEAR DONE FLAG, SELECT PRINTER,
LPPB=706606
IPRINT BUFFER, CLEAR BUFFER, SET ~ONE FLAG
ILOAD SPACING BUFFER CAC 15-17), SPACE
LPLS=706626
15ET DONE FLAG
.MED=3
.SCOM=10~

kHHH:'0
~'~HH"1

000e2

R
R
R

000~3

001304
000e5

00e~6

000?-7
00010

130011
00012
1301313
00014
00015
00016
00017
00020
00021
00022
e~0?3

R
R
R

R
R
R
R
R
R
R
R
R

~W024

0~025

tL~026

00027
00030
~"~I.3J

100525

001Zl00~

7413040
7 4 0040

A
A
A
A
A
A
A

74004(]J
740040
740040
740040
740040
740040
740C!l40
740040

A
A
A
A
A
A
A
A

600046
600523
600 Ci 12
600523

R
R
R
R
R

000000
000000
0000013
740~40

600'523
600V140

R
R

600'123
600512
600167

R
R
R

]~!'~~~

LPA.

.GLOBL LPA.
JMS
SWAP

o
€I

'"
LPSWCH
XX
LPWRD6
XX
LPTOUT
XX
1ST ART OF OATA REGISTERS.
IFOR SINGLE-USER DEVICES,
LPWD10
XX
XX
LV2WC
XX
LPSVAC
XX
LPWPC
XX
LPLBHP
XX
LP8CT
XX
LPWo17
XX
lEND OF DATA REGISTERS.
IBEGIN~"G OF FUNCTION DISPATCH TABLE.
JMP LPIN
JMP LPIGN
JMP LPERR
JMP LPIGN
JMF LPIGN
JMP LPCLOS
JMF LPIGN
JMP LPERR
LWRITE
JMP LPWRT
LV2FC
XX

IFOREGROUND BUSY REGISTER.
IBACKGROUND BUSY REGISTER
IFOREGROUND .CLOSE REGISTER.
IBACKGROUND .CLOSE REGISTER.
lION OR IOF
lION OR IOF OR DBR
IRETURN POINTER
IJMP FUNCTB
ICAL OWNER (0=F,1=B)
1.0AT SLOT NUMBER
IUNIT NUMBER (BITS 0-2) CAL ADDRESS (BITS 3-17)
IW14
IW15 - LiNE BUFFER ADDRESS.
IW16
IW17
I. I NIT
I.OPER - IGNORED.
I.SEEK - ERROR.
I.ENTER - IGNORED.
I.CLEAR - IGNORED.
I.CLOSE
I.MTAPE - IGNORED
I.READ <.REALR) - ERROR
I.WRITE <.REALW)
I.WAIT (.WAITR) PROCESSED COMPLETELY BY CAL HANDL

PAGE

LPA.

........,
I

N
N

2
Jr~P

0/032
00033
00034
00035
00036
00037

R
R

00040
00041

140:;'12
140434
750001
04043'3

R
R
A
R

R
R

~0042

R
R
R

00043
00044
00045

R
R
R

00046
00047
00050
00051

R
R
R
R

740v:4?

~v0531.

0?0000

R
R
A

~HHH'0e

~W~531

200M~2

600\764

750001

04\iW12
040e'31
2e0Mn

R
R
R

00052

00053
00054

060016
220604

040~53

00055

00056
00057
00060
00061
00062
00063
00064

R
R
R
R
R
R
R

120053
706501
000350
200062

040053
600063
200605

0401H'

R
R
R
R

A
R
R
R
R
R
R

SCOM35
LP~ERO

I.TRAN - ERROR
1ST OR AGE FOR .SCOM+35
IFGRD STOP 1/0 SUBROUTINE
18GRO STOP 1/0 SUBROUTINE
IHA"'JOLER 10

LPERR

LPSTP
LPSTP

171
LPTMPl
I.CLOSE LPT ROUTINE
DlM LV2WC
LPCLOS
O~M PGECNT
CLA!CMA
DAC LPIOAC
LAC (LPLS
LPSPCE
JMP LPCOMD
IINIT LPT ROUTINE.
LPIN
CLA!CMA
DAC LV2WC
DAC LV2FC
LAC (64
DACo LPA.+16
LAC* <.SCOM+55
LPIN2
OAC LPIN2
JMS* LPIN2
LP57T
LSDF
LPINT
LPWORD
LAC • +2
DAC LPIN2
LPHRTB
JMP .+1
LP3CHR
LAC (LPCB
LPCO~D
DAC LPIOT
ICOMMON EXIT SEQUENCE FOR CAL
lAND INTERRUPT LEVEL ENTRIES.
I
I

00065
00066
00067
00070
00071
011'072
011'073
00074
00075
00076
00077

R
R
R
R
R
R
R
R
R
R
R

00100

R
R

00101
00102
00103
00104.
00105
QhH06
00107

00110
00111
00112

R
R
R

100120
220606
040037
100571
200006
54016'5
741000
600100
120037
000007
000033
200033
060607
74017100
74\iH?00
21710f10

R
R

R
R
R
R

R
R

LPT.6

A
A
R

LPFCLR
LPBCLR

0401V12

0401 (~3
20043'5
74004"0
200(}13
703304

R
R
A
R
A

R
R

LPTIO

R
R
A

R
R
R

LPNOR

LPIOT

JMS
LAC*
DAC
JMS
LAC
SAO
SKP
JMP
JMS*
LPA.+7
SCOM35
LAC
DAC*
NOP

LPNRDY
(.SCOM+54
LPTMP1
LPRAIS
LPWRD6
LPDSR
LPT.6
LPTMPl

IFORM FEED.
IINITIALI2E #LINES/PAGE COUNTER
ISET UP TO 00 1/0 DURING
IPROTECTED EXIT.

ISET UP FOR FORM FEED ON INTERRUPT FROM LPCB.
152 (DECIMAL)---RETURN

ISTANDARD LINE BUFFER SItE TO USER.
- ONCE ONLY CODE.

I.SETUP - THESE 6 REGISTERS ARE OVERLAYED.

LEVEL

ICHECK IF DEVICE READY.
IADDRESS
10F CALL4
IRAISE TO API LEVEL 0, TURN PIc OFF.
IINTERRUPT
ICAL
IPC

SCOM35
<.SCOM+35

Nap

(NOP
LAC
LPFCLR
DAC
LPBCLR
OAC
LPIOAC
LAC
XX
LAC LPSVAC
DSK

IRESTORE IN INTERRUPT
IHANDLER FLAG.
INOP IF FGRD BUSY FLAG NOT TO BE CLEARED
INOP IF BGRD BUSY FLAG NOT TO BE CLEARED
IRESET
ISWITCHES.
lAC FOR lOT
IIOF OR lOT
IRESTORE AC.
IFROM LEVEL 0.

LPA.

0?121
00122

62:1271

R
R
R
R
R
A
A
R

00123

2?\~11~

0e124
00125

R
R

04v1163
2et1574

;:' \:' 11_ 3
114

4'70'70"i

~,~,

4e07l~fl

Z?115
V'Z116
0Z117

4e1011'"
4Q'10117

0v12~

e'70':'(A91

620?,~iJ7

7i'6f~1

e~126

~:;"1011 ~

e0127
00130

1010131
62012(11

R
R
R
R

XC'T

lION
lION

LP~.+5

XCT LPA.+6

OR rOF
OR lOF OR D8R

XCT
+.
XC T • + 1.

JMC".
LPNRDY

LPA.+7

0
LS~F

JMP~ LPNRQY
IDEVICE READY.
LAC LPIOT
ISAVE lOT.
OAC LPIOTB
LAC LP!OF
IEFFECTIVELY DEFER lOT,
D/lC LPIOT
JMS LP~SG
IINITIATE NOT READY REQUEST.
Jt-1 P * LPNROY
ISUSROUTINE TO C_lL A ROUTINE IN THE RESIDENT MONITOR TO
IINITIATE A ~OT READY REQUEST.
ICALLING SEQUENCE:
I
JMS LPMSG
I
RETURN wITH LPcTLR NON-0 IF REQUEST
I
HO~OREJ; 0 OTHERWISE.

N
\.N

00131
00132
021133
00135
100136
00137
100140
100141
010142
1010143
00144
1010145
010146
010146
vHH oi 6
00147
el01~el

1O{,0Vl~0

R
R
q
q

2010556

R
R
R

R
R

R
R
R
R
P
R
R

740201

A
R
A

LPMSG

LAC

620131

JMFo

1040556
200011
0410144
220611
1040037
1010571
1210037
7 4 10040
462 4 00
000000

DAC
LAC
DAC

LAC~

R
R
R

DAC
JMS

1000NH'
2(110154
200154

A
R
R

LPCTLR

S~A:C~A

JMS~

LPARG1

LPCTLR
LPA.+11
LPARGl
(.SCOM+64
LPTMPl
LPRAIS
LPTMPl

R
R

ITO API LEVEL 0, PIC OFF
IGO TO tR QUEUER
10=FGRD, l=BGRD

.LOC

140556
1010576
620131

IPOINTER TO tR QUEUER

.ASCII ILPI

.-1

LprRA+20~0~0

LPFRA+20~~00

100151
010152
1010153

ItR FLAG.
IAVOID DUPLICATE CALL.
I.ERR 4 ALREADY REQUESTED.
ISET tR IN PROGRESS FLAG.
10=FGRO, l=BGRD

LPCTLR
LPLOhR
LPMSG

R
R

IUNIT NUMBER
IRE TURN ADDRESS AT LEVEL 2
/SAME FOR RGRO
ITERMINAL ERROR. REQUEST NOT HONORED
IPIC ON, OE8REAK FROM LV 0

ISUBROUTINE FNTEREO AT API LEVEL 2. PIC OFF. WHEN tR FROM KEYBOARD
lIS ASSOCIATED WITH LINE PRINTER.

LPFRA

00154
0?155

000vH:~(II

140')56

rt~

~01'56

7066011

A
R
R
R
R
A

LSEF

~Wl157

6N~16?

00160
00161
..,0162

R
R

100131
600164
2lH,435

iHH63

740Vt4Vl

JMP
JMS
JMP

LPIOTB

LAC
XX

LPCTLR

ICLEAR tR FLAG

.+3

LPf'4SG
LPIOTB+l
LPIOAC

INOT REAnY CONnlTION
INOT CORRECTED.
lAC FOR lOT
IEXECUTE SAVED lOT.

PAGE

~1 ~116 4

f.'?
00166

R
R

7i7J07:42
703344

J v1 16 7

(",1170

R
R

(~0171

~Q1172

LPA.
~h~ 1

0"173
00174
""0175
00176
00177
00200
100201
00202
~~02(j13

00204
00205
00206
00207
00210
00211

R
R
R
R
R
R

R
R
R
R

7'? kHlVl 1

lil4~4')(Jl

R
R
R
R
A
R
R
R
R
R
R
R
R
A
R
A
R
R

0410212

777775
040062
140060

R
R

6?01~4

200(1"114
540612
6010176
765007
600513
220 01 15
500A13
04(1H"14
140012
440015
44V'l015
140V131
777770

I 0 ~\

A
LPOSR
IWRITE
LPWRT

LPOK

LPTSTR

'-I
I

..c:-

00212
0v.l213
00214
00215
00216
00217
00220
00221
00222
00223
00224
00225
1016226
160227
00230
~0231

00232
00233
V'~234

00235
00236
00237

R
R
R
R
R
R
R

R
R
R
R
R
R

777770
040016
200614
040304
440450
60023')
7770010
340014
0413014
741300
600301
22001t;
eJ40~~55

440015

A
R
R
R
R
R
A
R
R
A
R
R
R
R
R

2?VW1t;

R
R

040V'15A
440(i11t;

77777~

R
R
R

0 4 16 4 50
777770040057
200056

R
A
R
R

LPCONV

R
LPGET5
LPGET6

IFROM LEVEL 2
JMP".
LPFRA
LPT RDUTINE.
CLA!CMA
I IN! T REFORE CALL TO .LPCONV
OAr LP'5Cf-,
IDATA ~OOE SITS 15-17
LAC LPA.+14
SAn ( 2
JMP LPOK
IIOPS ASC I I
LAw 50~7
IILLEGAL DATA MODE.
JMP
LPER06+1
IWPC
LAC* LPLSHP
AND (3770100
DAC LPwPC
O~M LV2WC
IMOVE L. B. POINTER ( ! N USER'S
IS~ LPLBHP
IAREA) TO 1ST DATA WORD.
1St LPLBHP
O~M LV2FC
IIOPS ASCII MODE NO FORM CONTROL
LAW 177710
IINITIALltE SWITCH AT LPCONV
OAC LPCONV
LA~ 17775
13 CHAR. COUNTER FOR
13/6 WORD.
DAG LP3CHR
DiM LPWORD
ICLEAR DATA WORD.
ITHIS ROUTINE GETS THE
INEXT 7-BIT ASCII CHAR.
IF ROM THE 5/7 LINE BUFFER (USER'S AREA)
lIT RETURNS WITH IT RIGHT
IJUSTIFIED IN AN OTHERWISE
ICLEAR AC.
ILP5CH MUST BE SET TO
1777777 BEFORE THE INITIAL
ICALL TO LPCONV, LPWPC TO WPc INCLUDING HEADER,
ILPLBHP TO 1ST DATA WORD IN L.B.(USER'S AREA)
IINITIALI2ATION
LAW 17770
IFOR
DAC LP8CT
ICONTROL CHAR.
LAC (SAD LPCTAB
ISCANNING.
DAC LPVTST
IS~ LP5CH.
IMODIFIED FOR HOR. TAB.
JMP LPGET5
ITHIS 5/7 PAIR NOT EXHAUSTED.
LA~ 17000
TAO LPWPC
ISKIP ON NON 0.
DAC LPWPC
SNA!SPA
IWORD PAIRS EXHAUSTED
JMP LPEND
IPICK UP NEXT
LAC* LPL8HP
IWORO PAIR
OAC LP57T
IS~ LPLBHP
LAC* LPLBHP
OAC LP57T+1
ISl LPLBHP
LAW 17773
IRESET CHAR. COUNTER
IFOR THIS WORD PAIR
DAC LPt;CH
LAW 17770
DAC LP57T+2
IGO THROUGH SHIFT LOOP 7 1/2 TIMES .•
LAC LP'57T+l
n8f<

LPA.

PAG~

;. :124 0,

vW2 4 1

242
V10243

R
R

(:2244

VI~245

00246

R
R
R
R
R
R
R
R
R

74 Vi:' ~?
44 0v' =:; 7
6V10?4t:;
5(iH101 '5
6i'0?5:;
040V'5f.
2 C' .~ ,? 5"5

(,1.rl

~0247

002')0
00251
00252
00253
0.¥'l254
0.0255
0.0.256
00.25.7
00260
0121261
0.0.262
0.0.263
0.026 4
00265
1210266

HAL
~

ISf LP,)7T+2

JMP

R
R
R

ANn (177

04,' 7::;')

R
R
R

6eV?37
540fl::;
600.212
340.3,)7

741101?

R
R

340616

R
R

340.617

500621

7411~H~

A
R

240.?6(~

4409\62

R
R
R
R

6e0273

R
R
R

440012
040 4 35
20062?
600.064
742010
742010
7 4 2(i'lV'
51iH'l616

R
R
R
R
A
A

34~~62~

""'-.I
I

N
V1

0.CiJ267
00270
0121271
00272
00273
00274
00275
00276
00.277
0031il0

R
R
R
R
R
R
R

003vH
003~2

00303

013304
00305
00306
00307
00310
00311
00312
00313
00314
0111315

00316
00317
00320

04006~

R
R

600212

200t-2~

040012
60.0332

R
R

740?4!i1
600316
440304
440016
600304
540446
600301
540447

A
R
R
R

R
R
R

600212

R
R
R
R
R

R
R

2e0~1r,

04~H)31

600212

R
R

R
R
R
R

600.~21

LPCON1

6~0.30.4

IGOT CHARACTER.

LPCONl
DAC LP,)7T+1
LAC LP,)7T
RAL
DAC LP')7T
JMP LPGET6
SAD (177
JMP LPCONV
TAU LPM40
SPA
JMP LPVTST
TAD (777700
SPA.
TAn ( 4\11
TAD (1 00
AND (77
XQR LPWORD
1S2 LP3CHR
JMP LPCON3
JMF)

74 .,? 1.0

. +,

LPCON2

IDELETE RUBOUTS.
1-40

ICHAR. (.d0.---CONTROL CHAR.
1-1"H!1
1140-176 MAPPED INTO 100-136
16-BIT TRIMMED.
ICONSTRUCT 3/6 WORD.
13 CHARAcTER COUNTER.

IDATA. WORD COMPLETE.
IINDEX DATA WORD COUNT
1St: LV2WC
OAC LPIOAC
LAC (LPLO
JMP LPCOMD
ISHIFT CHARS. LEFT
RTL
LPCON3
RTL
RTL
lIN CASE LINK WAS ON.
AND (777700
OAC LPWORD
IGET NEXT CHAR.
JMP LPCONV
lEND OF CHARACTER STRING OR CARR. RETURN ( lOPS ASCII)
LPEND
LAC (47
OAC LV2WC
IpAD LAST WORD WITH SPACES.
JMP LPHT3
CHAR. IN AC.
ICONTROL CHARACTER ROUTINE.
XX
IS AD LPCTAB-SAD LPCTAB+7
LPVTST
IVERTICAL FORM CONTROL CHAR,
JMP LPFORM
ISAO LPCTAB+N-SAD LPCTAB+N+l
IS~ LPVTST
1St: LP8cT
JMP LPVTST
SAO LPCTAB+l?1
ICARRIAGE RETURN.
JMP LPEND
SAD LPCTAB+l1
IHORI~ONTAL TAB.
JMP LPI-IT
IDELETE MEANINGLESS CHAR.
JMP LPCONV
ICO~PUTE FORt-' CONTROL CODE A.NO PLACE
lIN LV2FC
LPFORM
LAC LP8CT
1 ... ,3. H. IN D. B.
OAC LV2FC
JMP LPCONV
ICONVERT HOR. TAB TO N SPACES, WHERE N IS THE NUMBER

LPA.
003:;Jl
0(11322
0032:;
~0324
~03?5

00326
00327
00330
00331
00332
00333
Vl0334
00335
00336
00337
00340
00341
00342

PAGE

2?0V,1?

744:i'1~

R
R

340r1?

340t'24

R
R

34006?

R
R
R

740300600326
34042'5
0 4 0(7;61
200626
0 4 0212
761004'"
440061
600263
77777111
040212
600212

R
R

R
R
R

00343
00344
00345
00346
00347
00350
00351
00352
00353
00354
00355
00356
00357
00360
00361
00362
00363
00364
00365
12!12!366
00367
00370
00371
1210372
00373
00374
00375
00376
1210377

R
R
R
R
R
R
R
R
R
R
R

0040~1

1210401

R
p

00402
00403

1210404

R
R
R

R
R

R
R
R
R

R
R

340f,2S

04QHH3
220~36

R
R
R
R
R

A
R
R
A

R
R
R

040007
200372
600361
600343

04~W13

R
R
R
R
A
A
A
R
R
R
R

200350
040007
140350
700314
750100
777740
340372
040005
220607
040033
750001
060607
2~0350

7412!21210
160036
706602
700042
200165
040006
140555
200001
340VlC1!?
74120V1

R
R
R

R
R
A
R
A
A
R
R
R

R
R
A

6004S1

200012
741200,
600451

R
A
R

INECrSSARY T (I HAVE THE NEXi CHAR. I r--. COLUr--~ 11.21,31.41.51 ...• 111.
LPHT
IOATA ~ORO GOU~T
LAC LV?WC
IX2
CLL!RAL
IX3
TAU LV2WC
TAn ( 4
TAn LP3CHR
ICURRE/lJT ",ORO CHAR, COUNTER.
TAn (777766
1-1~ (DECIMAL)
SMA!StA
JMP • -2
TAD LPOVRP
OAC LPHRTB
LPHT3
LAG (JMP LPHT2
nAC LPCC~~V
LAW 40
LPHT2
1St: LPHRTB
JMP LPCON2
LAW 17770
DAC LPCONV
JMP LPCONV
IINTERRUPT HANDLER.
DAG LPSVAC
ISAVE AC
LPPIC
LAC* LPtERO
ISAVE PC, L, EM, MP
DAC LPTOUT
LAC LPION
JMP LPSTON
IPIC ENTRY.
JMP LPPIC
LPINT
IAPI ENTRY, SAVE AC.
DAC LPSVAC
IPC, L, EM, MP
LAC LPINT
·DAC LPTOUT
DtH
LPINT
10=API ENTRY
IREAt) 1/0 STATUS
10RS
SMA!CLA
IPIC OFF -- SUlLO JOF
LPM40
LAW 17740
/PIC ON -- ION
TAD LPION
LPSTON
OAC LPSWCH
LAC* <.SCOM+35
OAC SCOM35
CLA!CMA
OAC* <.SCOM+35
LPINT
LAC
StA
IPIC ENTRY
LPtERO
DtM*
ICLEAR LPT DONE FLAG
LPCF
ION
IENABLE PIC
LPION
LAC LPOBR
DAC LPr4RD6
ICLEAR STOP 1/0 SWITCH
OtM
LPSTPS
LAC
LPA.+1
TAD
LPA.+2
SNA
100 NOT CONTINUE I/O IF
IBOTH 8USY FLAGS ARE 0
LPEMPT
JMP
IINITIATE MORE OUTPUT IF APPROPRIATE.
LAC LV2WC
LPTOK
SNA
JMP LPEMPT

LPA.

PAGE

4f115

7411(i1?

V'\" 4 fi'!6

6(~041?

JMP LPCLSE

~q407

540A27

SAil

0\'1410
00411
00412
e0413
00414
00.4:15
00416

60041~

JMP LPSPPR

600.?07

R
R
R

14k~01?

R
R

0~417

00420
00421
00422
.00423
00424
00425
100426

77772f:

34\434
74(:?01

R
R

21012P31
5410425

60.0430

500630

540630
140434

040435
777776

R
A

1040.031
60.0044

14001?
440434
2010('31

R
R

A
R
R
R

100427

IOl1430
00431
010432
100433

R
R
R

60.0064

R
R

010434

0000.100

00435

1010436

010437

R
R
R

777752
777761
777762
777753

A
A

777763

010440
010441
00442
100443
1010444
1010445
1010446
1010447
10104510

R
R

777764
77776rJ1
777754
777755
777751

100100.100.

A
A
A
A
A
A

1010451

11010476

220A3?
040.037

R
R

100571

R
R

004'12

100453
00454
00455
010456

R
R
R
R

12100.37

00457

11010576

2010633

R
R

SPA
(50

IBUFFER FULL,

JMP LPTSTR
LV?WC
lIS PAGE FULL?
177106
TAO PGECNT
IYES - FORM FEED
StA!CMA
LAC LV2FC
SAD LPOVRP
IOVERPRINT.
JMP LPOVER
AND (7
SAO (7
IINIT #LINES/PAGE CNT
DiM PGECNT
IVERT. SPACING BEFORE PRINTING
OAC LPyOAC
LPVMOV
LAl-i 17776
LPOVRP
OAC LV2FC
JMP LPSPCE
IWORD COUNT EXHAUSTED.
LPOVER
DtM LV~WC
IINCREMENT #LINES/PAGE CNT
1St PGECNT
IPRINT BUFFER.
LAC (LPPB
JMP LPCOMD
o
IINITIALltED TO 0 WHEN AT TOP OF FORM
PGEC"lT
I1NCREMENTED BY 1 UNTIL 58(1~) LINES
I
HAVE BEEN OUTPUT OR FORM FEED IS ENCOUNTERED
LPIOAC
o
ITABLE OF ASCII CONTROL CHAR'S'SCANNEO BY LPT IN lOPS ASCI I MODE
777752
ILF-EVERY LINE 0
---12
LPCTAB
---21
777761
IOC1-EVERY 2ND LINE 1
---22
777762
IDC2-EVERY 3RD LINE 2
---13
777753
IVT-EVERY 6TH LINE 3
---23
777763
IDC3-EVERY 10TH LINE 4
---24
777764
IDC4-EVERY 20TH LINE 5
777760
IDLE-OVER PRINT 6
---2~
---14
777754
IFF-TOP ON NEXT FORM 7
777755
ICR
---15
777751
IHT
---11
LP5CH
~
15/7 COUNTER
ISET UP SWITCH IN EXIT ROUTINE TO
ICLEAR FOREGROUND OR BACKGROUND BUSY REGISTER AS
IA FUNCTION OF WORD11, AND PLACE 10F IN LPT
IIOT REGISTER SO THAT NO ·NEW 1/0 WILL BE STARTED.
LPEMPT
JMS
CLFLAG
lIS THiS DEVICE INVOLVED IN 1/0 BUSY SITUATION.
IADDRESS OF
LPT31
LAC*
(.SCOM+52
IIIO BUSY TESTER
nAC
LPTI1Pl
IRAISE TO LEVEL 0 AND TURN OFF PIC
JMS
LPRA!S
LAC
(LPA.
JMS*
LPTMPl
JMS
LPLOWR

LPCLSE
LPSPPR

Dttl.l
LAW

IROUTINE TO DETERMINE 1F THIS 1/0
tWAS A REAL TIME REQUEST OR NOT.

LPA.

LAC
R
R
R

JMP
LAC
SA.G
SKP
JMP

0(~463

0~464

R
R

54W~1111

R
R

600065
220635
040037
Hi0"571

0~473

0V'474

00475

60QlVti"5
2Vi0f.,4

741?~(i'

465
0;'Q66
00467
0.0470
00471
0,0472

N
00

S:\J A

F
P

(i1,,~

"""-J

t?461
0(11462

00476
00.477
00500
00501
00502
00503
00504

00505
005~6

00507
005113
0~511

R
R
R

R
R

74H~9J(i\

200~17

120037
100576
6~~0.65

A
R
R
R
R
R
R
R
R

000~100

R
R
R
R
R
R
R
R
R
R
R

200.574
1340110

A
R
R

200CJ.11

740200
613135137
21313543
1340102
620.476
2013544
1340103
620476

R
R
R
R
R
R

IF REAL TIME.

LPW017

INOW

LPNOR
(JMP UIR I TE

INOT .REALW

LPW010

IJMP FUNCTION
/.REALw
INOT REAL TIME REQUEST.
IAOOR. OF
IREAL TIME PROCESSOR

LPNOR
<.SCOM+51
OAC
LPTMPl
JMS
LPRAIS
LAC
LPWD17
JMS*
LPTMPl
J~lS
LPLOWR
JMP
LPNOR
ISUBROUTINE TO SET UP CLEARING OF THE
IAPPROPRIATE BUSY FLAG (AT PROTECTED EXIT TIME)
lAND NULL (IOF) LINE PRINTER lOT
IREGISTER.
CLFLAG
0.
IIOF
LPIOF
LAC
LPIOT
OAC
IWORO 11 OF LIVE REGS.
LAC
LPA.+11
/0=FGRO, l=BGRD
S2A
JMP
.+4
IFOREGROUND
LPFBSY
LAC
LPFCLR
OAC
CLFLAG
JMP*
IBACKGROUND
LPBBSY
LAC
LPBCLR
DAC
JMP*
CLFLAG
LAC~

00516
00.517
00520
130521
00522

R
R

000512
765006
13413037
2013013
0413566
2130011
7413200
2013636
2413037
11313557

00523
00524

R
R

1130476
60006"5

005?5

~00~00

0~526

R
R

400V0"5

R
A

00512
00513
130514
~0515

R
R
R
R

R
R

LPERR=.
LPER06

IILLEGAL FUNCTIONS

(3131313

IBGRO

LAC

513136
LPTMPl
LPSVAC
LPTAUX
LPA.+11

SlA
LAC
XOR
JMS

LPTMPl
LPTERR

R
R
R
R

R
R

LA~

OAC
LAC
OAG

R
R

00.527
00530

70330.4
6213525

00531

0.013000

R
A

LPIGN

JMS
CLFLAG
JMP
LPNOR
ITHIS SUBROUTINE IS EXECUTED BY THE
ICAL HANDLER VIA WORD 0 OF THIS I/O
IHANOLER JUST PRIOR TO GIVING CONTROL
ITO THE HANDLER AT THE APPROPRIATE
IENTRY IN THF FU~CTION DISPATCH TA8LE.
SWAP
~
XCT
LPA.+5
ISTOP 1/0 SURROUTINE
LPSTP
~

lION OR IOF

IFROM LEVEL 0

OB~

.)MP *

ICLEAR BUSY FLAG

SWAP

LPA.
,/,,~5~2

VJ?33
fi~534

0:1535
~jl~536

0~537
0C~54Vl

00541
0Vl542
00543
00544
~H154 5
00546
00547
00550
00551
005')2
00553
00554
00555
00556

PAGE

R
R

lH~C:;;71

.)MS

2(7;\I!')5A

LAC
StA:CLA
JMP
LAC
TAr
SlA!CLA
CMA
OAC
OlM
OtM
OtM
OlM
alM
jMS
LAC
StA
jMP
jMP*
0

w
R
R

7'50?'i'?

6'?!0')4?

R
R

R
R
R
R
R

3407;0?
75J20V'

R
R

R
R
R

R
R

R
R
R
R

200001

74 l CJ,0:1

R
A
A

04 55')

14~i 'Hoi

140002
140 0 03
140004
140556
10!0576
200555
740200
600'551
620531
000000
000000

R
R

LPCLER
LPFBSY
LP88SY

R
R

R
A
R

R
A

LPSTPS
LPCTLR
I
I

'J
I

1..0

00557
00560
00561
00562
00563
00564
00565
00566
00567
00570

R
R
R

R
R
R
R
R

R
R

000~00

040564
220637
040037
100571
740040
120037
740040
100576
620557

A
R
R
R
R
A
R
A
R
R

LPRAIS
LPCTLR
LPCLER
LPA.+1
LPA.+2
LPSTPS
LPA.+1
LPA.+2
LPA.+3
LPA.+4
LPCTLR
LPLOWR
LPSTPS
.-2
LPSTP

0~575

00576
'00577
00600
0060.1

000000

R
R
R

200640
705504
7VHHl02
620571

vH~0~eJeJ

703304
700042
620576

R
R

R
A

706(:.2f>

A *L IT
A *L IT

0vHH'64

00604
~0605

706')02

006Q'6

000154

00607

00013~

0~603

R
A

0e100~~

R
R
R

0060~

0001')~

*LIT
-L IT
A *LIT
A -LIT
A
A

IIF 1/ 0 IS UNOrR WAY SET
ISTOP SwITCH.

ICLEAR

1/0

BUSY SWITCHES.

ICLEAR CLOSE SWITCHES.

/'R FLAG
IALLOW INTERRUPTS.
IWAIT UNTILL I/O IS DONE.

/STOP I/O SWITCH,
/,R IN PROGRESS IF NON-0.

ISUBROUTINE TO CAUSE OUTPUTTING OF ERROR MESSAGE.
LPTERR
0
/LAW CODE
LPTLAW
OAe
<.SCOM+66
LAC*
LPTMPl
OAC
IRAISE TO API LEVEL 0 AND TURN OF PIC.
JMS
LPRAIS
ILAW CODE
XX
LPTLAW
jMS*
LPTMPl
XX
LPTAUX
JMS
LPLOWR
jMP*
LPTERR
I

00571
00572
00573
00574

IPROTECT
100 "JOT HANG IF
IfR IN PROGRESS.

ISUBROUTINE TO RJ\ISE TO API LEVEL 0
lAND TUR~ OFF PIC.
LPRAIS
0
(400200
LAC
ISA
LPIOF
IOF
jMP*
LPRAIS
ISUBROUTINE TO DEBREAK FROM API LEVEL 0
lAND TURN ON PIC.
LPLOwR
0
OBK
ION
LPLOWR
JMP*
.END

LPA.

PAGE
0'1610

740·~?'0

0~611

~~ .~ 61 '2
vH613

R
R

0?0:lf:l4
000V02

IiL"'614

0'~615

R
R

t~616

"""'J
I

\.N

011617
00620
00.621
00622
00623
0vl624
00625
00626
00627
00630
00631
00632
00633
00634
00.635
00636
00.637
00640

R
R
R

R
R
R
R
R
R
R
R

R
R
R
R

R
R

377000
5421 4 36
000.177
77770,11
000c:'!40

000100
000077
706546
00.017>47
1000((1;;'4
777766
600335
0000'50
000007
706606
000152
000000
600030
000151
003000
000166
400:?00

A *LIT
A *LIT
A

*LIT

A *LIT
R *LIT
A *LIT
A *LIT

A *LIT
A *LIT
A *LIT
A *LIT
A *LIT
A *LIT
1. *LIT
R *LIT
A *L IT
A *LIT
A *LIT
A *LIT
R *LIT
R *LIT
A *LIT
A *LIT
A *LIT
A *LIT

NO ERROR LINES

LPA.

'-J
I

~
~

PAGE

11
p

CLC:-L~~:

~Q'476

LP aRC>.
LPA.
LPR8S'

;')0144

~~~V1~

0V'!544

LP8CL~

?'V"H13
706502

LPCB
LPCF
LPCLER
LPCLOS
LPCLSE
LPCOM[)
LPCONV·
LPCO!'-41
LPCON2
LPCON3
LPCTAB
LPCTLR
LPOSR
LPEMPT
LPEND
LPERR
LPER06
LPF8SY
LPFCLR
LPFORM.
LPFRA
LPGET5
LPGET6
LPHRTB
LPHT
LPHT2
LPHT3
LPIGN
LPIN
LPINT
LPIN2
LPIOAC
LPIOF
LPION
LPIOT
LPIOTB
LPLBHP
LPLO
LPLOwR
LPLS
LPL1
LPL2
LPMSG
LPM4e
LPNOR
LPNROY
LPOK
LPOVER
LPOVRP
LPPB

7066V'2

00542
0""040

0~412

00064
00212
00252
00263
00273

R
R

~'le4~6

R
R
R
R

0~5'56

0~165

R
R

00451
003V'1

000512
00512
00543
00102
00316
00154
00235
00237
00061
00321
00335
00332
00523
000 4 6
00350
00053
00435
00574
00372
00110
00163
00015
706546
00576
706626
706566
706526
00131
00357
0~065

00120
00176
0e430
00425
706606

R
R
R
R
R
R
R
R
R
R

R
R
R
R
R
R

R
R
R

R
R
R
A

R
A
A
A

R
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R
R
R
A

"""-J

I
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LPA.

PAGE

LPPIC
LPRAIS
LPSPCE
LPSPPR
LPSTOI\J
LPSTP
LPSTPS
LPSVAC
LPSWCH
LPTAUX
LPTERR
LPTIO
LPTLAW
LPTMP1
LPTOK
LPTOUT
LPTSTR
LPT.6
LPT31
LPVMOV
LPVTST
LPWD10
LPWD17
LPWORD
LPWPC
LPWRD6
LPWRT
LPZ!ERO
LP3CHR
LP5CH
LP57T
LP8CT
LSDF
LSEF
LV2FC
LV2WC
LWRITE
PGECNT
SCOM35
SWAP
.MED
.SCOM

00343
00571
00044
00413
00361
00531
00555
00013
00005
00566
00557
00070
00564
00037
,00402
00007
00207
00100
00452
00424
00304
00010
00017
00060
00014
00006
00167
0f(1036
00062
00450
00055
00016
706501
706601
00031
00012
00030
00434
00033
00525
000003
000100

12
~

R
R
R
R

R
R
R

R
R
R
R
R

R
R
R
R

R
A

A
R
R

R
R

R
R
A

LPA.

PAG~

LPA.
,MEO

01'2>71

00?l7~

A
.-<

LPSWC~1

0ee?5

LPwR06
LPTOUT

0re26
0ee(7
0?312
0??12

LPW01~

LV2WC
LPSVAC
LPWPC
LPLBHP
LP8CT
LPW017
LWRITE
LV2FC
SCOM35

""-J
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'-."4

~ 3

q
Q

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R
q
q

00014
0NH5

R
R

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0~~17

000:;2

R
Ii

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LP~ERO

00036

LPTMPl
LPCLOS
LPSPCE
LPIN
LPIN2
LP57T
LPWORO
LPHRTB
LP3CHR
LPCOMO
LPNOR
LPTIO
LPT.6
.SCOM
LPFCLR
LPBCLR
LPIOT
LPNROY
LPMSG
LPARG1
LPFRA
LPIOTB
LP08R
LPWRT
LPOK
LPTSTR
LPCONV
LPGET5
LPGET6
LPCONl
LPCON2
LPCON3
LPENO
LPVTST
LPFORM
LPHT
LPHT3
LPHT2
LPPIC

01!'037

R
R
R

00.043

00033

00044

00046
00053
000'55
00060
00061

R
p

0~062

R
R
R

00064
00065

00070
00100
000100
00H".2
00103
00110
00120
00131
00144
00154
00163

R
R

R
R
A

R
R
p

R
R

R
q

~0165

00167

0~176

00207
00212
00235
00237
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00273

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0~304

ee316
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00332
00335
00343

R
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p

R
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"""-J
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\JJ
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LPA.

PAGE:

LPI"r
LP"'4'?
LPSTO\
LPION
LPTOK
LPCLSE
LPSpPR
LPVMOV
LPOVRP
LPOVER
PGECNT
LPIOAC
LPCTA8
LP5CH
LPEMPT
LPT31
CLFLAG
LPERR
LPER06
LPIGN
SWAP
LPSTP
LPCLER
LPFBSY
LP88SY
LPSTPS
LPCTLR
LPTERR
LPTLAW
LPTAUX
LPRAIS
LPIOF
LPLOWR
LSDF
LPCB
LPL2
LPLD
LPL1
LSEF
LPCF
LPPB
LPLS

003'50
00357
00361
0e372

14
R
R

R
R

00402
00412
00413
00424
00425
00430
00434

0~435

R
R
R

00436
00450
00451
00452
00476
~00512

00512
00523
00525
00531
00542
0~543

00544
00555
00556
00557
00564
00566
00571
00574
00576
706501
706502
706526
706546
706566
706601

R
R

R
R
R

R
R
R
R
R
R

R
R
R
R
R

R
R
R
R
R
A
A

A
A
A

7066~2

A
A

706606
706626

A
A

SECTION 8
SYSTEM GENERATION
The system utility program .SGEN, used to tailor a
Background/Foreground tape to operate in different hardware configurations, is not available at this time.

8-1

APPENDIX I
.SCOM REGISTERS

The function of the .SCOM (§ystem COMmunication) Registers
is to provide, among the various program elements of the
Background/Foreground Monitor System, an easily accessible
set of registers which contain communication pointers, data
words, and program flags indicating the state of the system.
The .SCOM table begins at location lfiYfiY8 within the Resident
Monitor.

Location lfiYfiY is referred to as .SCOM or .SCOM + •

and the (N+ l)th register is referred to as .SCOM + N.
Each .SCOM register has a special meaning and format.
present, there are about 115

such registers.

Slots at the

end will be allotted for future expansion as needed.
REGISTER DEFINITIONS:

The following list indicates the

contents of each .SCOM register.

Those which are fixed at

assembly or system generation t:ime and never changed are
marked by (F).

Some .SCOM registers must have a Foreground

value and a Background value.

Therefore, their contents must

be swapped from one to the other, depending upon which job
has control.

They are flagged by (S).

have been reserved for future software.

Some .SCOM registers
If their contents

(format) a:e as yet unspecified, they will be flagged with
(U) •

.SCOM + fiY

(F)

Pointer to the highest register in core
(37777, 57777, or 77777).

I-I

.SCOM + 1

(a) Address just above the Resident Monitor
when the Non-resident Monitor has been loaded
for Foreground.
(b) Address just above the Foreground job
when the Resident Monitor has loaded the Nonresident Monitor in the Background.
If the
system program PIP is called, this will be
the first location of its .DEV table.
(c)
For DDT in the Background this points
to the start of its symbol table.

. SCOM + 2

(S)

(a)

Same as (a) for .SCOM + 1 .

(b)
Normally used by user and system programs to indicate the first (lowest) location
in free core.
(c)
For DDT in the Background this points to
the first location after the symbol table,
which is also the first Location of free core.
.SCOM + 3

(S)

.SCOM + 4

Normally used by user and svsteIl! prog.rams ___ _
to indicate the last (highest) locatIOn--fn
free core. For the Foreground, this is also
the highest location allocated to the Foreground job.
Bits indicate machine configuration:

(F)
(F)

(F)
(U)
(F)
(F)

Bit ~l
Bit 1
Bits 2-5
Bit 6 2

fJ=NO API; I=API
fJ=No EAE i l=EAE
fJ
(Reserved and unused)
~=7-channel MAGtape
1=9-channel MAGtape
Bit 7
~=Bank Mode (PDP-9)
Bits 8-13 Unassigned
Bit 14
l=Background/Foreground
Bits 15-17 Drum size for RM~9=
~=No drum
1=32K (RM,0'9A)
2=6SK (RM,09B)
3=13IK(RM,eJ9C)
4=262K(RM~9D)

5=S24K(RM,09E}
lThe presence or lack of EAE is determined dynamically by the
Resident Monitor.
27/9-channel default operation may be set by Foreground Keyboard
command.
1-2

.SCOM + 5

(a)
Initially this points to RESINT, the
address of the initialization section in
RESMON.
The paper tape bootstrap loader
transfers control indirectly through this
location.
(b)
When calling the System Loader to
bring in a system program, the Non-resident
Monitor stores here the code number of the
program to be loaded.
(c) When running a system program, its
start address is stored here.
(a)
When the Non-resident Monitor calls
the System Loader to load user programs,
bits ~ - 2 indicate which command was
,given to the Monitor:

.SCOM + 6

$LOAD, $GLOAO, $DOT, or $DDTNS.
Bit ~
1 if $OOT or $DDTNS (DDT load)
Bit 1 = ~ if $LOADi Bit 1 = 1 if $GLOAD
Bit 2 = ~ if $DDTi Bit 2 = 1 if $DDTNS
(b)
When the user programs have been
loaded, the start address of the main
program is stored here.
The load command
code bits (~-2) remain as in (a).
The interrupted PC plus L,XM,MP are saved
here for DDT in the Background when CTRL T
has been typed .

.SCOM + 7

. SCOM +

(S)

The interrupted PC plus L,XM,MP are saved
here after a. NORMAL CTRL P has been typed
and honored .

. SCOM + 11 (F)

Bootstrap restart instruction .

. SCOM + 12 (F)

Pointer to the 339 Pushdown list within
the Resident Monitor.

1-3

·SCOM + 1) (F)

Pointer to the .IOIN 1 table in the Resident Monitor.

.SCOM + 14 (F)

Pointer to the .MUD 2 table in the Resident Monitor.

. SCOM + 15 (F)

Pointer to the .BFTAB 3 table in RESMON .

.SCOM + 16 (F)

Pointer to .DATF 4 , Foreground .DAT slot
~, in the Resident Monitor.

.SCOM + 1'7 (F)

Pointer to .DATB 4 , Background .DAT slot
~, in the Resident Monitor.

. SCaM + 2fJ (U)

Reserved for PDP-15 .

. SCOM + 21

MAGtape status register .

. SCOM + 22

Reserved for MAGtape handler •

.SCOM + 23 (F)

Twos complement size of the Monitor's transfer
vector table (used by system generator) .

. SCOM + 24 (F)

Pointer to the Monitor's transfer vector
table (used by System Generator).

1.IOIN is the table which indicates which I/O devices are in core,
which units on each device are spoken for, and which job (Background
or Foreground) owns them.
2. MUD is a table listing all available multi-unit device handlers,
with pertinent information about those handlers.
3. BFTAB is a buffer table containing pointers to and the sizes of
all external I/O buffers that were set up by the loaders.

4.DATF is the Device ~ssignment Table for Foreground .
. DATB is the Device ~ssignment Table for ~ackground.

1-4

(a)
Prior to loading the Foreground job,
the amount of free core requested by the $FCORE
command is stored here.
If no $FCORE command
is given, the default assumption is 2 registers.

·SCOM + 25

(b)
After the Foreground job has been loaded,
this register contains a pointer to the register immediately above the Foreground core area .
. SCOM + 26

(S)

Contains ~ if Foreground is in control and 1
if Background is in control .

. SCOM + 27

(F)

Pointer to lOT Skip literal table in the
Monitor (used by System Generator) .

. SCOM + 3.0 (F)

Pointer to PI Skip Chain.

.SCOM + 31

(a)
The Software Memory Protect Bound set
from .SCOM + 25 after the System Loader has
loaded the Foreground job.
(b)
Set to point just above the Background
I/O handlers and I/O buffers after the Background job has been loaded.

.SCOM + 32

(a)
Pointer to the Hardware Memory Protect
Bound (or where it should be set).
Contents
(. SCaM + 32) 3 contents (. SCaM + 31).

. SCOM + 33

Background Program Counter, including L,XM,MP .

.SCOM + 34 (F)

Address of the resident teletype handler

.SCOM + 35

Interrupt Service Flag. Non-~ indicates that
control is in some interrupt service routine .

. SCOM + 36

(F)

(TTA).

Bits to tell the teletype handler which units
are model 33 (specific bit = ~) and which
model 35 (specific bit = 1). Bit ~ corresponds
to unit ~; bit 1 to unit 1; and so on.

1-5

.SCOM + 37 (F)

. SCOM +

. SCOM + 41

Pointer to CALER. Used to detect attempt
to re-enter CAL handler and to trap CAL*
instructions .
CAL Flag. Non-~ if control is in the CAL
handler (indication necessary for interrupt
servicing) .
"Who's running in the Background" Flag .

Bit ~ = 1 if a Loader is running.
Bits 1-17:

17777
~

2
3

4
5
6

7
10
11
12
13
14
15

Non-resident Monitor
user program or DDT
EDIT
MACRO
PIP
F4
SGEN
DUMP
UPDATE
CONV
MACROA
F4A
EXECUTE
CHAIN
PATCH

. SCOM + 42

Level 5 (API, Foreground) busy register .
Zero indicates level 5 non-busy. Non-zero
indicates that Foreground level 5 is idle
waiting for some I/O to complete. Set non-~
with the initial address of the device handler
doing the I/O.
If the device is teletype,
the unit number + 4~~~~~ is stored here instead .

. SCOM + 43

Same as .SCOM + 42 for Foreground level 6 .

. SCOM + 44

Same as .SCOM + 42 for Foreground level 7 .

. SCOM + 45

Same as .SCOM + 42 for Foreground Mainstream
level.

I-6

·SCOM + 46

Foreground level 5 I/O satisfied flag.
Zero indicates that level 5, which was I/O
bound, can be started up again .

. SCOM + 47

Same as .SCOM + 46 for level 6.

. SCOM + 5.0

Same as .SCOM + 46 for level 7 .

. SCOM + 51 (F)

Pointer to REALTPI in the Resident Monitor .

. SCOM + 52 (F)

Pointer to IOBUSy 2 in the Resident Monitor .

. SCOM + 53 (F)

Pointer to LV4 Q 3 in the Resident Monitor .

. SCOM + 54 (F)

Pointer to CALL4 4 in the Resident Monitor .

. SCOM + 55 (F)

Pointer to .SETUp s in the Resident Monitor .

. SCOM + 56 (F)

Pointer to GETBUF 6 in the Resident Monitor .

lREALTP is a subroutine to process real-time requests.
2 IOB USY

is a subroutine to check for I/O busy termination.

3 LV 4Q queue is a list of I/O handlers which are waiting to complete their interrupt service processing at API level 4.

4CALL4 is a subroutine to initiate an API level 4 request.
5. SETUP is the routine initially called by all I/O handlers
to set up skips in the PI skip chain or API channel registers.

6GETBUF is a routine called by the I/O handlers which assigns
buffer areas to the handlers via .BFTAB.

1-7

.scaM + 57

non-~,

a pointer to the entry point of

the last Mainstream Foreground real-time

subroutine in the chain of subroutines to
be run when Foreground Mainstream gets control .
. SCOM + 6,0

Pointer to the entry point + 1 of the first
subroutine in the chain of Foreground Mainstream real-time routines to be run when
Foreground Mainstream gets control.

. SCOM + 61

Same as .SCaM + 57

for Background .

. SCOM + 62

Same as .SCaM +

for Background .

.scaM + 63

Argument for API instruction ISA when interrupts at API software levels are to be requested.

. SCOM + 64

(F)

.scaM + 65

. SCOM + 66

Pointer to CR.QR l

in the Resident Monitor .

Set non-~, while a Foreground user program is
running, to indicate that the resident buffer
may not be used by the Foreground. The resident buffer must be available to the Background,
which presumably changes jobs more often, for
U:3e by the Monitor and the Loaders.
(F)

Pointer to ERRORQ2 in the Resident Monitor .

.SCOM + 67 (F)

Pointer to Foreground control character table
in TTA .

. SCOM + 7,0 (F)

Pointer to Background control character table
in TTA.

lCR.QR is a routine called by I/O handlers to initiate a devicenot-ready request.
2ERRORQ is a routine called to enter information in the Foreground
and/or Background error queue. and to set the error flags in
.SCOM + 71.

1-8

.SCOM + 71

.SCOM + 72

Error flag.
The following conditions exist
if the respective bit = 1:
~ - Background error
1 - Foreground error
2 - Background terminal error
3 - Foreground terminal error
(F)

Pointer to the Foreground error processing
subroutine plus the 2~~0J0 bit to turn on
extend memory after a DBR .

. SCOM + 73 (F)

Same as .SCOM + 72 for Background error
subroutine .

. SCOM + 74

Saved argument for Foreground error routine
ISA instruc·tion .

. SCOM + 75

(F)

Contains JMS IGNORE, a call to a dummy interrupt service routine, used during error processing .

. SCOM + 76 (F)

Twos comple:ment count of the number of teletypes on the machine.

.SCOM + 77

$SHARE Flag (to allow Background to share
Foreground I/O bulk storage units. Nonzero indicates that SH~RING is allowed.

. SCOM + 100 (F)

Pointer to ENTERQl in the Resident Monitor .
Will contain ~, instead, if ENTERQ routine
not assembled into the Monitor .

. SCOM + 101

If set non-zero by the Foreground keyboard
command, $MPOFF, Background enters EXEC
mode.
The memory protect boundary register
is zeroed to allow Background to modify and
transfer to any location in core. Background
IOT's will still trap to the Monitor but the
IOTws will be executed.

lENTERQ is a subroutine which makes entries in the API queue.

1-9

1~2

(U)

Unused

.SCOM + 1~3 (U)

Unused

· SCOM + 1~4

Unused

· ;;COM +

(U)

. SCOM + 1.05 (F)

Twos complement size of the PI skip chain .
(Used by System Generator) .

· SCOM + 1.06 (F)

Pointer to the register immediately above
the Resident Monitor (set by the Non-resident
Monitor after it has built the .MUD table) .

.SCOM + 1.07
.SCOM + 11.0
. SCOM + 111

Used to store the file directory entry
block of the XCT file to be EXECUTE'd
in the Foregr?und .

.SCOM + 112
.SCOM + 113
. SCOM + 114

Used to store the file directory entry
block of the XCT file to be EXECUTE'd
in the Background .

.SCOM + 115 (F)

Maximum number of teletypes allowed, which
is a function of an assembly parameter in the
Monitor (Used by System Generator).

1-10

APPENDIX II
ERRORS

ERROR HANDLING IN BACKGROUND/FOREGROUND
The processing of errors detected by the Resident Monitor,
I/O handlers, the Linking Loader and the System Loader has
l>(~(~n

chanqcd in the Background/Foreqround Sys tern from the way

they are treated in the Keyboard and I/O Monitor Systems.
The most significant chang'e is the introduction of terminal
and non-terminal errors.

A terminal error stops execution of the

job associated with the error.

This causes all I/O handlers

assigned to that job to be called to stop I/O that may be in
progress and all Monitor queues to be cleared of entries for
that job (Background, Foreground or both).
A non-terminal error is one that does not necessarily
warrant aborting the operation of the offending job.

A non-

terminal error message is entered into a queue for the appropriate job and is printed on the appropriate control teletype
when that unit is free.

While the printing of non-terminal

error messages is pending or in progress, operation of the offending job is suspended.

Thi~j

restriction does not apply to

I/O handlers, which may continue interrupt processing.
The format for error messages generated by the Resident
Monitor, I/O handlers and the Loaders is:
.ERR

HNN

XXXXXX

11-1

where NNN = error code
XXXXXX = auxiliary information
These errors are tabulated on pages 2-4,-5,-6 and-7.
Errors detected by the FORTRAN Object Time System (OTS) are
formatted as follows:
.OTS NN
where NN

error code

OTS errors are listed on page 2-8.
CONTINUATION AFTER ERROR
.OTS errors are terminal errors.

After OTS has printed

the error message, it exits to the Monitor.

Therefore, after

an .OTS error the user does not have the option of restarting
his program.
Non-terminal .ERR errors do not terminate the operation of
user programs.

Continuation, following the printing of the error

message, is automatic.
Terminal .ERR errors terminate the operation of user programs.
After the printing of the error message, the user has the option
of typing CTRL P (to restart his program at the CTRL P restart
address), CTRL T (to return to DDT), CTRL Q (to take
a dump of memory), or CTRL C (to return to the Monitor to

11-2

load another job).

If the error occurred while control was

in the Non-resident Monitor or in a Loader, the user does not
have the options indicated above.

The Monitor will automatically

be reloaded.
ERROR CALL
Routines that wish to set up an error condition, I/O device
handlers for example, should use the following coding sequence:
LAC *
DAC.
LAC
ISA
IOF
LAW
JMS*
AUXARG XX
DBK
ION

(.SCOM + 66
TEMP
(4~f02~fO

CODE
TEMP

/POINTER TO ERRORQ
/SUBROUTINE.
/RAISE TO API
/LEVEL ~.
/SEE BELOW.
/CALL ERRORQ.
/AUXILIARY ARGUMENT.
/RETURN HERE.

The calling program must be operating with memory protect
disabled in order to be able to issue lOT's.
The first argument, given in the AC to ERRORQ, may be
loaded either by LAW code or by

Code

h~C

code in the following format:

Bits fO-5 are ignored
Bit 6
fO means non-terminal error
Bit 6
1 means terminal error
B-Lt 7
1 means Background error
nit 8
1 means Foreground error
Bits 9-17 is a 3-di g it error code

both bits (7 and 8)
may be set to 1

To avoid the possibility of future conflicts, user programs
and device handlers should utilize codes 6fOfO - 777.

1I-3

The auxiliary argument, following the JMS to ERRORQ,
will be printed in the error message as a 6-digit octal number.
The error message will be printed in the form:
.ERR

NNN

XXXXXX

where NNN = the 3-digit error code
XXXXXX = the 6-digit auxiliary information
The actual printing of the error message and processing
of the error will be done only after all interrupt processing
has ceased and when control is no longer in the CAL handler.

BACKGROUND/FOREGROUND MONITOR ERRORS (.ERR)
The following abbreviations are used below in describing
the auxiliary information:
L - bit ~ is the status of the link
XM- bit 1 is the status of extend memory
MP- bit 2 is the status of memory protect
CAL AI,DR - bits .3-17 contain the address of the CAL in error.

ERROR NO.

AUXILIJ>..RY
INFORMAT.ION

TERMINAL

ILLEGAL CAL FUNCTION

L, XM, MP, CAL ADDR

YES

CALl ILLEGAL

L, XM, MP, CAL ADDR

YES

.DAT SLOT ERROR (erroneous
.DAT slot number or .DAT
slot not tied to an I/O
handler)

L, XM, MP , CAL ADDR

YES

ILLEGAL INTERRUPT

ERROR

XM, MP,

YES

IThe auxiliary information, depending on the source of the error,
is sometimes UNIT i, CAL ADDR.

11-4

ERROR NO.
~~4

AUXILIARY
INFORMATION

ERROR

TERMINAL