SUB

Syntax: SUB R

Where R can be any of the general purpose registers (A,B,C,D,E,H andL)

Byte: 1byte

Addressing Mode: Register Addressing

Working: 

1. 

2. 

3. 

4. Flag

Example: SUB B 

where [B] = 11H 

and [A]= 22H

After execution of SUB B

[A] = 11H 

[B] = 22H

Program: write an ALP for 8bit subtraction  of values present in Registers A and B where A carries 44H and B carries 30H. Store result at memory location 5000H.

Label  Mnemonics  Comments

Start: SUB B 

          STA 5000H 

 Stop: HLT

Output: [5000H]= 14H

LXI H, 4000H ; 4000= 90h

MOV A,M ; a= 90h

INX H ; 4001h where 4001= 40h

MOV B, M ; b= 40h

SUB B ; a= a - b ... A = 90 - 40= 50h

INX H ; 4002h

MOV M,A ; 4002h = 50h

HLT