2] Arithmetic Instructions
The instructions in this group are used to perform various arithmetic operations on 8/16 bit data. The instructions in this group affect conditional flags (CF, AF, PF, SF, OF) in flag register.
1] ADD
This
instruction is perform addition of destination & Source and stored result
in destination. The source can be 8/16 bit register, memory location or
immediate data (number). Destination can be 8/16 bit register, memory location.
This instruction affect all 6 conditional flags.
Destination =
Destination + Source
Example, ADD
AL,04H ……(AL = AL + 04)
ADD
AL,BL ……(AL = AL + BL)
ADD
AH,[2000]
ADD
[4000],AX
1) Program Title: - WALP to 44H & 57H in AL & BL register
respectively, perform the addition & store the sum on memory location
[2000]. DS = 0200H
Register & Memory Address Used: - AL, BL & [2000]
Data: - 44H, 57H &
0200H
|
Address |
Op-code |
Label |
Mnemonic |
Operand |
Comments |
|
|
|
|
MOV |
AX,0200 |
Initialization of DS |
|
|
|
|
MOV |
DS,AX |
|
|
|
|
|
MOV |
AL,44H |
;COPY 44H IN AL |
|
|
|
|
MOV |
BL,57H |
;COPY 57H IN BL |
|
|
|
|
ADD |
AL,BL |
;ADD CONTENTS OF BL WITH AL
& RESULT SOTRED IN AL |
|
|
|
|
MOV |
[2000],AL |
COPY CONTENTS OF AL ON MEMORY
LOCATION [2000] |
|
|
|
|
INT |
03 |
STOP |
Result:-
DS : OFFSET : DATA
0200: [2000]
: 9B
2) Program Title: - WALP to 1122H in AX & 4455H in SI register,
perform the addition & store 16 bit result of addition on memory location
[3000]. DS = 0400H
Register & Memory Address Used: - AX, SI & [3000]
Data: - 1122H, 4455H &
0400H
|
Address |
Op-code |
Label |
Mnemonic |
Operand |
Comments |
|
|
|
|
MOV |
AX,0400 |
Initialization of DS |
|
|
|
|
MOV |
DS,AX |
|
|
|
|
|
MOV |
AX,1122H |
;COPY 1122H IN AX |
|
|
|
|
MOV |
SI,4455H |
;COPY 4455H IN SI |
|
|
|
|
ADD |
AX,SI |
;ADD CONTENTS OF AX WITH SI
& RESULT SOTRED IN AX |
|
|
|
|
MOV |
[3000],AL |
COPY CONTENTS OF AL ON MEMORY
LOCATION [3000] |
|
|
|
|
INT |
03 |
STOP |
Result:-
DS : OFFSET : DATA
0400: [3000]
: 77H
0400: [3001]
: 55H
3) Program Title: - WALP to 99H & 88H in AL & BL register
respectively, perform the addition & store the result of sum on memory
location [2000]. DS = 0200H
Register & Memory Address Used: - AL, BL & [2000]
Data: - 99H, 88H &
0200H
|
Address |
Op-code |
Label |
Mnemonic |
Operand |
Comments |
|
|
|
|
MOV |
AX,0200 |
Initialisation of DS |
|
|
|
|
MOV |
DS,AX |
|
|
|
|
|
MOV |
AL,99H |
;COPY 99H IN AL |
|
|
|
|
MOV |
BL,88H |
;COPY 88H IN BL |
|
|
|
|
ADD |
AL,BL |
;ADD CONTENTS OF BL WITH AL
& RESULT SOTRED IN AL |
|
|
|
|
MOV |
[2000],AL |
COPY CONTENTS OF AL ON MEMORY
LOCATION [2000] |
|
|
|
|
INT |
03 |
STOP |
Result:-
DS : OFFSET : DATA
0200: [2000]
: 21 H
2] ADC
Syntax –
This
instruction is perform addition of destination & Source plus Carry Flag
(CF) and stored result in destination. The source can be 8/16 bit register,
memory location or immediate data (number). Destination can be 8/16 bit
register, memory location. This instruction affects all 6 conditional flags.
Destination
= Destination + Source + CF
Example, ADC
AL,04H ……(AL = AL + 04 + CF)
ADC
AL,BL ……(AL = AL + BL + CF)
ADC
AH,[2000]
ADC
[4000],AX
4) Program Title: - WALP to 99H & 88H in AL & BL register
respectively, perform the addition & store the 16 bit result of sum on
memory location [2000] & [2001]. DS = 0200H
Register & Memory Address Used: - AL, BL, [2000] & [2001]
Data: - 99H, 88H &
0200H
|
Address |
Op-code |
Label |
Mnemonic |
Operand |
Comments |
|
|
|
|
MOV |
AX,0200 |
Initialization of DS |
|
|
|
|
MOV |
DS,AX |
|
|
|
|
|
MOV |
AL,99H |
;COPY 99H IN AL |
|
|
|
|
MOV |
CL,00H |
;COPY 00H IN CL |
|
|
|
|
MOV |
BL,88H |
;COPY 88H IN BL |
|
|
|
|
ADD |
AL,BL |
;ADD CONTENTS OF BL WITH AL
& RESULT SOTRED IN AL |
|
|
|
|
ADC |
CL,00H |
;00H ADD WITH CONTENTS OF CL &
CARRY FLAG (CF) |
|
|
|
|
MOV |
[2000],AL |
COPY CONTENTS OF AL ON MEMORY
LOCATION [2000] |
|
|
|
|
MOV |
[2001],CL |
COPY CONTENTS OF CL ON MEMORY
LOCATION [2001] |
|
|
|
|
INT |
03 |
STOP |
Result:-
DS : OFFSET : DATA
0200: [2000]
: 21 H
0200: [2001]
: 01 H
3) SUB
Syntax: - SUB Destination, Source
This instruction subtracts operand from destination
operand and stores result in destination operand. The source can be 8/16 bit
register, memory location or immediate number. The destination can be 8/16 bit
register or memory location. This instruction affects all 6 conditional flags.
For example
SUB
AL, 04H
SUB
AL, BL
SUB
AL, [2000]
SUB
AX, BX
SUB
[2000], CL
SUB
AL, [SI]
4) SBB
Syntax:- SBB Destination, Source
This instruction subtracts source operand
from destination operand and also subtracts carry (borrow) flag from result.
The result is stored in destination operand. The source can be 8/16 bit
resister memory location or immediate number. The destination can be 8/16 bit
resister or memory location. This instruction affects all conditional flags.
For Example
SBB AL,BL
5) MUL
Syntax :- MUL Source
This
instruction is used to perform multiplication of data stored in al or ax
register & source operand. The result of multiplication is stored in AL or
AX. The source can be 8/16 bit register or memory location. (for 8/16 bit
multiplication one number is in AL/AX & another number is given in source
operand.) The multiplication of two 8 bit numbers can be of 16 bits. Therefore
the result of multiplication is stored in AX register. Similarly the result of
multiplication of two 16 bit numbers can be of 32 bits. Therefore for 16 bit
multiplication the result in stored in AX and DX register. The LSW (least
significant word) of result is stored in AX register & MSW (Most
Significant Word) of result is stored in DX register. This instruction affects
only carry flags.
For
example
MUL BL I.e.
AX=AL*BL
MUL BX i.e.
DX:AX=AX*BX
MUL [2000] i.e.
AX=AL*[1000]
6) DIV
Syntax :- DIV Source
This instruction is used to perform division of a 16 bit number stored in AX and 8 bit number specified in source operand OR a 32 bit number stored in DX:AX registers and 16 bit number specified in source operand. In 8086 only two division operations i.e. 16/8/ and 32/16 are allowed.
For 16/8 division the result is stored in AX register. For 32/16 division the result is stored in DX: AX registers. The source can be 8/16 bit register or memory location. This instruction affects all conditional flags. For example
DIV BL i.e. AX= AL/BL
DIV BX i.e. DX: AX = DX: AX/BX
7) CMP
Syntax :- CMP Destination, Source
This instruction is used to compare number in destination operand with number in source operand. The comparison is actually performed by subtracting source operand from destination operand. But the result of comparison is not stored anywhere. The source can be 8/16 bit register, memory location or immediate number. The destination can be 8/16 bit register or memory location. The result of comparison is reflected (shown) in 3 flags i.e. carry flag, sign flag and zero flag. Table below shows status of this 3 flags after compare instruction
CF SF ZF
Destination =Source 0 0 1
Destination >Source 1 0
0
Destination <Source 1 1 0
The examples of this instruction are
CMP AL, 05H
CMP AL, BL
CMP AL, [1000]
CMP
AX, BX
0 Comments