how-to-do-addition-and-subtraction-in-assembly-language
assembly-language-math-operations-addition-subtraction
code:
.model small
.stack 100h
;for defining varaiable
.data
a db 'Enter the first number:$'
b db 'Enter the secont number:$'
c db 'add: $'
d db 'sub: $'
.code
main proc
mov ax,@data ;initialize data segment
mov ds,ax ;move to the data segment register
;print first string
mov ah,9
lea dx,a ;it loads the address of a variable or memory location into a register.
int 21h
;input first number from the user
mov ah,1
int 21h
mov bl,al
;Backup first user input for subtract part
mov bh,bl
;for new line
mov ah,2
mov dl,10
int 21h
mov dl,13
int 21h
;print the second string
mov ah,9
lea dx,b
int 21h
;input secont number from the user
mov ah,1
int 21h
mov cl,al
;Backup second user input for subtract part
mov ch,cl
;for new line
mov ah,2
mov dl,10
int 21h
mov dl,13
int 21h
;--------adding part---------
;for print result string
mov ah,9
lea dx,c
int 21h
;for add
add bl,cl
;convert ascii for display
sub bl,48
;for print
mov ah,2
mov dl,bl
int 21h
;-------subtract part--------
;for new line
mov ah,2
mov dl,10
int 21h
mov dl,13
int 21h
;print result string
mov ah,9
lea dx,d
int 21h
;restore orginal input from backup
mov bl,bh
mov cl,ch
;subtract
sub bl,cl
;check if result is negative
js negative_result ;jump if sign sf = 0 positive, sf=1 negative
;if rusult is positive
add bl,48 ;convert to ascii for display
;for print sub result
mov ah,2
mov dl,bl
int 21h
jmp done
negative_result:
neg bl ;make the result positive
add bl,48 ;convert to ascii for display
mov ah,2
mov dl,'-'
int 21h
mov dl,bl ;print the number
int 21h
done:
exit:
mov ah,4ch
int 21h
main endp
end main
result:
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