Search code examples
assemblyx86-16factorial

Factorial of a number in assembly

I am trying to find Factorial of a number but a unexpected output is coming. for 5 it should be 120 but 00 is coming. please Help in the following code Sometimes it goes into infinite loop.

.model small
.stack 100h
.data
buffer db 10 dup('$')
n dw 5  
.code
main proc 

    mov ax , @data
    mov ds ,ax
    mov ax , n
    mov bx , offset buffer
    mov cx , 1 

 l1 : 

inc cx  
mul cx
cmp cx , n
jne l1

l2 : 
mov dx, 0 
mov cx ,10  
div cx 
add dl,48 
mov [bx], dl 
inc bx
cmp ax, 0 
jne l1      

mov dx , offset buffer ; moving address to dx
mov ah,9 ; printing string
int 21h

mov ax, 4c00h
int 21h


main endp
end main
Solution

  • The jump at the end of your l2 loop is incorrect. You're jumping to l1 when you should be jumping to l2.

    Also, in your l1 loop you inc and mul before you decide whether to exit the loop. So in the case where n is 5 you'll get 5 * 2 * 3 * 4 * 5 (which is 600).