Objective
Write a Program to Multiply Two 16 Bit Numbers in Assembly language . Program will ask for two numbers to be multiplied and should store those numbers in AX and BX Registers . Now it should implement certain logic to both numbers to find the result.
Consider that a word of data is present in the AX register and 2nd word of data is present in the BX register. We have to multiply the word in AX with the word in BX. Using MUL instruction, multiply the contents of the 2 registers. The multiplication of the two 16 bit numbers may result into a 32 bit number. So result is stored in the DX and AX register.
The MSB of result is stored in the DX register and LSB of result in AX register.
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AX = 1234 H
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1234 H
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BX = 0100 H
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´
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0100 H
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23400 H
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Algorithm to Multiply Two 16 Bit Numbers
Step I : Initialize the data segment.
Step II : Get the first number in AX register.
Step III : Get the second number in BX register.
Step IV : Multiply the two 16 bit numbers.
Step V : Display the result.
Step VI : Stop
Multiply Two 16 Bit Numbers Flow Diagram
Program to Multiply Two 16 Bit Numbers
.model small
.data
a dw 1234H
b dw 0100H
.code
mov ax, @data ; Initialize data section
mov ds, ax
mov ax, a ; Load number1 in ax
mov bx, b ; Load number2 in bx
mul bx ; multiply numbers. Result in dx and ax
mov si, ax
mov bx, dx ; Result in reg bx
mov dh, 2
l1: mov ch, 04h ; Count of digits to be displayed
mov cl, 04h ; Count to roll by 4 bits
l2: rol bx, cl ; roll bl so that msb comes to lsb
mov dl, bl ; load dl wth 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
dec dh
cmp dh, 0
mov bx, si
jnz l1
mov ah, 4cH ; Terminate Program
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 . More assembly language codes can be found here.
C:\programs>tasm 16-mul.asm
Turbo Assembler Version 3.0 Copyright (c) 1988, 1991 Borland International
Assembling file: 16-mul.asm
Error messages: None
Warning messages: None
Passes: 1
Remaining memory: 438k
C:\programs>tlink 16-mul
Turbo Link Version 3.0 Copyright (c) 1987, 1990 Borland International
Warning: No stack
C:\programs>16-mul
00123400
Rambo says
It’s Label
Master says
where is l4 ?