GCD of Two Numbers program in Assembly Language
Write a Program to find the GCD of Two Numbers in Assembly Language . Program should load two registers with two Numbers and then apply the logic for GCD of two Numbers . GCD of two numbers is performed by dividing the greater number by the smaller number till the remainder is zero. If it is zero, the divisor is the GCD if not the remainder and the divisor of the previous division are the new set of two numbers. The process is repeated by dividing greater of the two numbers by the smaller number till the remainder is zero and GCD is found.
Algorithm for GCD of Two Numbers
Step I : Initialize the data segment.
Step II : Load AX and BX registers with the operands.
Step III : Check if the two numbers are equal. If yes goto step X, else goto step IV.
Step IV : Is number 1 > number 2 ? If yes goto step VI else goto step V.
Step V : Exchange the contents of AX and BX register, such that AX contains the bigger number.
Step VI : Initialize DX register with 00H.
Step VII : Perform the division operation (contents of AX / contents of BX).
Step VIII : Check if there is remainder. If yes goto step IX, else goto step X.
Step IX : Move the remainder into AX register and goto step IV.
Step X : Save the contents of BX as GCD.
Step XI : Display the result.
Step XII : Stop.
GCD of Two Numbers Algorithm Snapshot
Program code for GCD of Two Numbers
.model small
.stack 100
.data
no1 dw 0120
no2 dw 0090
gcd dw 0h
.code
mov ax,@data ; initialize DS
mov ds, ax
mov ax, no1 ; get the first number
mov bx, no2 ; get the second number
again: cmp ax, bx ; check if nos are equal
je endd ; if equal, save the GCD
jb exchg ; if no,
; is AX ; if yes interchange
l2: mov dx, 0
div bx ; check if ax is
; divisible by bx
cmp dx, 0 ;
je endd
mov ax, dx ; mov the remainder
; as no1 data
jmp again
exchg : xchg ax, bx jmp l2
endd : mov gcd, bx
mov ch, 04h ; Count of digits to be
; displayed
mov cl, 04h ; Count to roll by 4 bits
l12: 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 ; INT 21H
; (Display character)
int 21H
dec ch ; Decrement Count
jnz l12
mov ah, 4ch
int 21h
end
How to Run this Program
For Running this program you should have installed Tasm on you computer . If you have not installed Tasm yet please install from Here .
C:\programs>tasm gcd.asm
Turbo Assembler Version 3.0 Copyright (c) 1988, 1991 Borland International
Assembling file: gcd.asm
Error messages: None
Warning messages: None
Passes: 1
Remaining memory: 437k
C:\programs>tlink gcd
Turbo Link Version 3.0 Copyright (c) 1987, 1990 Borland International
C:\programs>gcd
001E
