Digital PDFs

DIGITAL-8-22-U

December 1965

4 pages

Original

0.2MB

Document:	digital-8-22-u-d
Order Number:	DIGITAL-8-22-U
Revision:
Pages:	4
Original Filename:	https://svn.so-much-stuff.com/svn/trunk/pdp8/src/dec/digital-8-22-u/digital-8-22-u-d.pdf

OCR Text

IDENTIFICATION
I .I

Digi’rGI-8-22-U-Sym

Unsigned Decimal Print

I .3

June 7, I965

PUP-B
LIBRARY

Digital-8-22-U-Sym
Page 2
2

AB? TRACT

This subroutine permits the typeout of the contents of a computer word as a

4—digit, positive, decimal integer.
3.
3:

REQUIREMENTS
I

Storage
This subroutine requires 38 core locations.

3.3

Equipment
Basic PDP—8 with ASR 33.

USAGE

4.I

Loading
The subroutine may be placed in core by use of the

Digital-8-2-U-Rim for full details.
user

4.2

Binary Loader.

See

The symbolic tape provided is either assembled with the

program or separately with the proper origin setting.

Cialling Sequence
The subroutine is called by the usual JMS instructionwith the number to be

printed in the AC.

Return to the location following that of the calling JMS.

RESTRICTIONS (Not Applicable)

DESCRIPTION

6.I

Discussion

This is a basic subroutine used to obtain decimal output corresponding to binary
words in memory.

The program operates in a straightforward manner.

First the binary equivalent

negative result is obtained. A count is
kept of the number at subtractions necessary to accomplish this, thus yielding the most significant
decimal digit.
This process is repeated—-using the proper power often, to give the three re—
maining decimal digits.

of IOOO is subtracted from the original number until

METHOD

7.I

Discussion

This method of binary to binary coded decimal conversion is compact and easily
The latter consideration is of little consequence since the

understood if it is not sophisticated.

subroutine is output limited.

Digital-8—22-U-Sym
Page 3
8.

FORMAT

8.3

Output Data

Output is in the form of four consecutive decimal digits. No sign is printed.
Spacing, tabulation, carriage return, etc. are not provided for in this subroutine. See
Digital—8-19-U-Sym, which contains short subroutines for the latter purposes.
9.

EXECUTION TIME

9.3

Average
This subroutine is output limited.

10.

PROGRAM

10.4

Program Listing

/PDP-8 UNSIGNED DECIMAL PRINT
/CALL WITH NUMBER TO BE TYPED IN AC
/RETURN TO LOCATION FOLLOWING CALLING JMS
0200

0000

0201

3243

DCA VALUE

0202

3244

DCA DIGIT

0203

1235

TAD CNTRZA

DECPRT,

0204

3245

DCA CNTRZB

0205

1234

TAD ADDRZA

0206

3213

DCA ARROW

0207

7410

SKP

0210

3243

DCA VALUE

0211

7100

CLL

0212

1243

TAD VALUE

0213

1235

0214

7430

0215

2244

ISZ DIGIT

0216

7430

SZL

0217

5210

JMP ARROW-3

0220

7500

CLA

0221

1244

TAD DIGIT

0222

1242

TAD K250

0223

5041

TSF

0224

5223

JMP .—1

0225

5045

ARROW,

TAD TENPWR

/SAVE INPUT
/CLEAR

/SET COUNTER To FOUR
/SET TABLE POINTER

/SAVE

/SUBTRACT POWER OF TEN

SZL

/DEVELOP BCD DIGIT
/LOOP
/HAVE BCD DIGIT
/GET DIGIT
/MAKE IT ASCII
/OR TAD DIGIT
/JMP TDIG: SEE 8—19-U—SYM
/TYPE DIGIT
=

Digifa 1 -8-22-U-Sym
Page 4
0226

7600

0227

3244

DCA DIGIT

0230

2213

ISZ ARROW

CLA

0231

2245

ISZ CNTRZB

0232

5212

JMP ARROW-1

0233

5600

JMP l DECPRT

0234

1236

TAD TENPWR

0235

7774

0236

6030

ADDRZA,
CNTRZA,
TEN PWR,

—4

4750

0237

7634

-0144

0240

7766

—0012

0241

7777

-0001

0242

0260

0243

0000

0244

0000

0245

0000

11.

DIAGRAMS (N01L Applicable)

12.

REFERENCES

K260,
VALUE,
DIGIT,
CNTRZB,
$

/CLEAR
/UPDATE POINTER
/DONE ALL FOUR?
/NO:CONHNUE
/YES: EXIT
/ONE THOUSAND
/ONE HUNDRED
/TEN
/ONE

260
o
o

Digital-8-19-U—Sym. Teletype Output Subroutines