Basic Computer Instruction Formats
Adapted from Figure 5-5, Computer System Architecture, Third Edition by M. Morris Mano, 1993, Prentice Hall.

 

Basic Computer Instruction Set

Symbol

Hexadecimal code

Description / binary (register operations)

 

I = 0, I = 1

 

AND

0xxx 8xxx

AND memory word to AC

ADD

1xxx 9xxx

Add memory word to AC

LDA

2xxx Axxx

Load memory word to AC

STA

3xxx Bxxx

Store content of AC in memory

BUN

4xxx Cxxx

Branch unconditionally

BSA

5xxx Dxxx

Branch and save return address

ISZ

6xxx Exxx

Increment and skip if zero

CLA

7800

Clear AC /
0111100000000000

CLE

7400

Clear E /
0111010000000000

CMA

7200

Complement AC /
0111001000000000

CME

7100

Complement E /
0111000100000000

CIR

7080

Circulate right AC and E / 0111000010000000

CIL

7040

Circulate left AC and E / 0111000001000000

INC

7020

Increment AC /
0111000000100000

SPA

7010

Skip next instruction if AC positive / 0111000000010000

SNA

7008

Skip next instruction if AC negative / 0111000000001000

SZA

7004

Skip next instruction if AC zero /
0111000000000100

SZE

7002

Skip next instruction if E is 0 /
0111000000000010

HLT

7001

Halt computer /
0111000000000001

INP

F800

Input character to AC

OUT

F400

Output character from AC

SKI

F200

Skip on input flag

SKO

F100

Skip on output flag

ION

F080

Interrupt on

IOF

F040

Interrupt off

Adapted from Table 5-2, Computer System Architecture, Third Edition by M. Morris Mano, 1993, Prentice Hall.

BACK