CS401 assignment no 2 spring 2011

[saneha]

[org 0x0100]

jmp start

num: db 117 ; 8bit number
NumMask: db 255
start: mov bl, [num] ; Copies 117 to bx register
not bl ; Inverting number to get 1’s complement using NOT
add bl,1 ; adding 1 to 1’s complement to get 2’s complement

; Inverting bits using XOR
mov dl, [num]
xor dl, [NumMask]
add dl, 1

mov ax, 0x4c00 ; terminate program
int 0x21

Another solution of this question is

[org 0x100]
jmp start
number: dw 13

start:
mov ax,[number]
xor ax,0xffff
inc ax
mov ax,0x4c00
int 21h