2s Complement of a Numbers Assembly Program
2s Complement of a Numbers Algorithm
Step I : Initialize the data memory.
Step II : Load the number in AX.
Step III : Initialize counter = 16 in CX.
Step IV : Rotate number by 1 bit position to left with carry.
Step V : Complement carry.
Step VI : Decrement count.
Step VII : Check if count = 0. If not goto step IV
Step VIII : Rotate once again by 1 bit to restore original carry back.
Step IX : 2’s complement = 1’s complement in AX + 1
Step X : Display result.
Step XI : Stop.
2s Complement of a Numbers Assembly Code
.model small
.data
a dw 1234H
.code
mov ax, @data ; Initialize data section
mov ds, ax
mov ax, a ; Load number1 in ax
mov cx, 16 ; Load CX with count
up: rcl ax, 1 ; Rotate ax by 1bit to left with carry
cmc ; find 1's complement of bit
loop up ; check if all bits complemented, if not goto up
rcl ax, 1 ; return carry back to original position
add ax, 1 ; 2's complement=1's complement+1
mov ch, 04h ; Count of digits to be displayed
mov cl, 04h ; Count to roll by 4 bits
mov bx, ax ; Result in reg bx
l2: rol bx, cl ; roll bl so that msb comes to lsb
mov dl, bl ; load dl with data to be displayed
and dl, 0fH ; get only lsb
cmp dl, 09 ; check if digit is 0-9 or letter A-F
jbe l4
add dl, 07 ; if letter add 37H else only add 30H
l4: add dl, 30H
mov ah, 02 ; Function 2 under INT 21H
; (Display character)
int 21H
dec ch ; Decrement Count
jnz l2
mov ah, 4cH ; Terminate Program
int 21H
end
