8086 Program for 2's Compliment of a number

    

Explanation :

·          We have a number. Let this number be stored in register AX. Our task is to find 2’s complement of this number. We use NEG instruction. It replaces the number in AX with 2’s complement of the number in AX, directly.

                        eg. :  AX = 1234 H.

NEG AX  =

1110

1101

1100

1100

= EDCC H

·          2’s complement of 1234 H = EDCC H

     Algorithm :

Step I       :    Initialize the data memory.

Step II     :    Load the number in AX.

Step III   :    Find 2’scomplement of number.

Step IV    :    Display the result.

Step V     :    Stop.

Flowchart:

 Program :                                                                                           

.model small                                                            

.data

a dw 1234H

.code

       mov     ax, @data               ; Initialize data section 

       mov     ds, ax

       mov     ax, a                      ; Load number1 in ax                          

       neg      ax                         ; find 2's compement. Result in ax

       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

Result :

C:\programs>tasm 2'scomp.asm

Turbo Assembler  Version 3.0  Copyright (c) 1988, 1991 Borland International

Assembling file:   2'scomp.asm

Passes:            1

Remaining memory:  438k

C:\programs>tlink 2'scomp.obj

Turbo Link  Version 3.0 Copyright (c) 1987, 1990 Borland International

Warning: No stack

C:\programs>2'scomp

EDCC

C:\programs>