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DEC-12-FRZB-D

July 1970

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Document:	CREF12
Order Number:	DEC-12-FRZB-D
Revision:	0
Pages:	12
Original Filename:	http://bitsavers.org/pdf/dec/pdp12/diagnostics_set2/DEC-12-FRZB-D.pdf

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IDENTIFICATION

Product Code:

DEC-12-FRZB-D

Product Name:

CREF12

Date Created

July 1, 1970

Maintainer:

Software Services

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DEC-12-FRZB-D
July, 1970

1970 by Digital Equipment Corporation

The material in this handbook, including but not
limited to instruction times and operating speeds,
is for information purposes and is subject to change
without notice.

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

PDP
FOCAL
COMPUTER LAB

The equipment described herein is covered by patents
and patents pending.

For additional copies order DEC-12-FRZB-D from Program
Library, Digital Equipment Corporation, 146 Main Street,
Maynard, Massachusetts 01754
Price $1.00

1.0

INTRODUCTION

In many situations of assembling, debugging, and modifying programs, a crossreference listing is an invaluable aid.

This listing is particularly useful

when a programmer wishes to make changes in a large program or one he does not
know well.
A cross-reference is an alphabetical listing of all user-defined symbols with the
line numbers at which the symbol was defined and used.

Thus, the various places

that a tagged location or an equated symbol is used are easily identified.
C:REF12 provides this facility to the DIAL-Ms 1 user.

It should be noted that the usefulness of a CREF (CRoss-REFerence) is almost
directly proportional to the quality of the coding.

In particular, the follow-

ing principles should be used in new coding in order to make the best use of
r P.EF12:
Use symbolic references for beta registers, auto-index regi>ters,

page zero constants and temporaries, and fixed core locatioi1s.
2.

Avoid use of large displacements from a tag (e.g., TAD X+l2 or
JMP Y-6) because references to X and Y, respectively, rather than

the locations actually used, will appear in the CREF.
2.0

ENVIRONMENT

CREF12 (including its header) occupies seven blocks in the DIAL file area of any
unit.

It is loaded into locations J through 2777 of field 1 and is entered at

2§!1.0 rn field 1.
3.0

USING CREF12

cREF12 is fntended for use in conjunction with the LISTAPE pseudo-op of the
DIAL-MS AssernbleL.

L_ISTAPE (with a positive argument) produces a normal

assembler listing on a mass-storage device, rather than on the console Teletype(R)
or line printer.

The resulting data may then be processed by CREF12 to produce

a full cross-reference of user-defined symbols and, optionally, the assembly
listing.
To use CREF12, insert a LISTAPE n pseudo-op in the program of interest, where
n is an expression whose value is between /3 and 45, octal, and is taken as the
RTeletype is a registered trademark of Teletype Corporation.
1 LAP6-DIAL-MS is commonly referred to as DIAL-MS.

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unit number of a scratch tape
ing will be produced.

(fl-7)

or disk (ljK-45) on which· the Assembler list-

The user must exercise caution in assigning units for

LISTAPE because the listing information is written directly on the unit starting
at block zero without regard to anything else that may be on the same unit.
Therefore, unit n Should be either a scratch tape or a logical disk devoted to
scratch work.
Typing ret1rn at any time (after answering the "LISTING [Y OR N]? 11
causes CREF12 to return to DIAL-MS.

3.1

question

Operating Procedures
1.

Set all six sense switches on. Be sure the tape or disk unit
assigned by the LISTAPE pseudo-op is ready and WRITE ENABLEd.

Assemble the program with the LIST Command (refer to the LAP6-DIAL
Programmer's Reference Manual, DEC-12-SE2D-D).

If a printer is to be used for the CREF, it should be ready at
this time. When the Editor display returns, load CREF12 by
typing +LO CREF12 ,JK)

The following message is printed:
UNIT #?

Type an octal number between ~ and 45, followed by carriage return,
for the unit on which the listing was written.
The next message is

LISTING [YORN)?
Type Y if the full assembly listing and CREF are
the CREF is needed.

desired~

N if only

Assuming the specified unit is available and ready, CREF12 will then read the
listing (printing it if requested) and print the cross-reference table.
Output will be on. a .line printer if one is available and ready.
Otherwise, it will be on the console teletype.
3.2

Error Conditions
;

Under some conditions, CREF12 will not be able to produce the cross-reference
desired.
1.

If there were errors in the assembly, CREF12 may interpret the
program incorrectly, or may even be unable to process it at
all.
In the latter event, it will print "BAD INPUT" and return
to DIAL.:.;MS.

If there is· a large number of symbols and references, the cross-,
reference table may overflow.
In this case, CREF12 prints:

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·,;i:

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SYMBOL TABLE OVERFLOW AT LINE XXXX

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wh:,rc XXXX is the last line number processed. crmF'l2 t::hcn
pr .. nts the crqss-reference up to that line, and returns to
DIAL-MS. '!'his problem will arise if (NSYM*5 + NREF) is greater
than 4,094, where NSYM is the number of user-defined symbols in
the program, and NREF is the number of references to user-defined
s~mbols.
If t~ere are ~1ore than 8_1_0 10 symbols, this message
will occur during the first pass,
with XXXX equal to .0.0.0.0.
CREF12 will print "BAD INPUT" and return to DIAL-MS.

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3)

If the unit specified by the user is invalid, the DIAL-MS
I/O routines will display NO.

The user may type return to get back to DIAL.

If a program containing a LISTAPE pseudo-op is to be assembled without getting a
CREF, use the normal assembly procedure with the sense switches off; this
disables the LISTAPE function.
4.0
i. ter

INTERNAL DESCRIPTION
reading the

DIAL~MS

I/O routines into 7.0fiJ0-7777 of field 1, CREF'.1.2 requests

two parameters from-the user:

the unit from ,Jhich to read tile listing,

and whether the listing is to be pr:i.11.ted; CREF12 then begins its first
pass over the data.
The routine MAIN rewinds the input, initializes counters,
and cal·!:: t.he subroutines GETLIN and ENDLST to get a line of input and
check tt for tli.e separator between the listing proper and
the symbol table, respectively.

·1·nis separator is a line with one of two

messages, "NO ERRORS" or "XXXX ERRORS".

If the input runs out (indicated by a

word of zero) before the separator is found, the input is invalid and processing
is terminated with the message "BAD INPUT".
takes over and reads the symbol table.

If the separator is found, SYMBUILD

Each symbol is stored in stripped ASCII

form in field .0, followed by two words of zero.
When the end of data is found, control passes to PART2, which rewinds the input
file.

MAJOR calls GETLIN and ENDLST to get successive lines from the file and

test for the end of the listing proper.

After checking for the separator, MAJOR

flows into SCAN, which collects a symbol at NAME, calls NSERCH to search the
symbol table for it, and (if it finds the symbol) stores the line number with
the symbol in field ,0.

Control returns to SCAN until either carriage return,

slash, or "TEXT" is found.

Control then returns to MAJOR to get a new

line.
When a separ<'l.tor is found, control transfers to DUMP~ which prints a header, then
reads each symbol from the file.

Each symbol and its value.are printed, followed

by the line number at which the symbol was defined, and then the

lin~

numbers

at which the references to it were made.
Output is terminated, and control returns to DIAL-MS, when the end of the symbol

table is found.

The functions of minor routines are as follows:
BOP UP

Maintains SYSCOUN'r to keep track of field fl utilization and
issue the message "SYMBOL TABLE OVERFLOW AT LINE XXXX" when
the symbol table overflows. Called by SCAN when a reference is
to be added to the symbol table •.

CRLF

Go to a new line on the Teletype or line printer.

GETBLK

Get .8 blocks from the input file. {,Jsed by GETLIN when the inpur
buffer is empty, and by MAIN and PART2 to rewind the input and
read the first buffer load.

GETC

Obtain the next character from the current line and return it in
CHAR and the AC. Used by many routines.

GETLIN

Get a line (a string of characters terminated by zero or line
feed) from the input file.
If LISTSW is non-zero, print it.

I MOVE

Move a block of data across field boundaries.
to move a new entry into the symbol table.

I PUSH

Move. a portion of the symbol table down. Durinq SYMBUILD, the
symbol table is built by pushing previous entries down to lower
core addresses and entering each new symbol at the end of the
list (at the top of field~).
During SCAN, references to each
symbol are stored following the symbol.
IPUSH .is called to make
room for each entry.

ISNUM

Examine the first four characters of the current line.
If not
octal digits, return to P+l. Otherwise, convert them to binary,
store.binary at LINENO, and return to P+2. Called only by MAJOR.

I ZERO

Search.the symbol table, starting at the location addressed by
TEMP, for a word of zero.
If none is found, return to P+l.
Otherwise, return to P+2 with TEMP pointing to the zero.
Called by NSERCH to look for the next symbol and by SCAN to find
the .end of the references to the current symbol.

LIMIT

Compare the value in the AC to two limits.
If the AC is zero,
return to address in P+3~ if AC is out of limits, return to
address. in P+4.
If AC is within the limits, return to P+5.. Used
by many routines.

NSERCH

Find the symbol table entry which matches the symbol at NAME.
Return to P+l if no match is found, or to P+2 if successful.
Called only by SCAN.

POCTAL

Print the value in the AC, converted to octal characters. Used
by BOPUP to print the line number at which overflow occurs and
by DUMP to print the cross-reference line numbers.

PUTC

Print one character on the output- devl.ce.

TTY

Print a character string.

RE TC HU

Check. the keyboard flag and return to DIAL
if retµrn has been struck. Otherwise just
clear AC.

Used by SYMBUILD

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HOW TO OBTAIN SOFTWARE INFORMATION
Announcements for new and revised software, as well as programming notes, software problems, and document a·
lion corrections are published by Software Information Service in the following newsletters.

Digital Software News for the PDP·8 Family
Oigital Software News for the PDP·9/ l 5 Family
PDP-6/PDl'· I 0 Software Bulletin

!'Ill'"' newsklters con lain information applicable to software available from l>igital's Program Library.

l'lea:,e complete the card helow to place your r,ame on the newsletter mailing list.

Oue:;tiDm or problems concerning DEC Software should be reported to the Software Specialist at your nearest DEC
'"''•onal or district sales office. In cases where no Software Specialist is available, please send a Software Trouble
Ecport form with details of the problem to:
Software Inkn',1dli«11 '.)ervice
Digital Equipment Corpc·,1ati•.•n
14(> Main Street. Bldg. 3·5
Maynard, Mas>ad1usctts 01754
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llt"d hy lektypc output as wl'il as listings or tapes of the user program to facilitate a complete investigation. i\n
an',\V\'I will he sc·nt to the individual and appropriate topics of general interest will be prinlL'd in lhe newsletter.

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a \\I'll'<' list will ht• 111d11ded twice yt·arly. !Jirect all inq11irics and req11ests to.
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CREF12
READER'S COMMENTS

DEC-12-FRZ.13-D
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