Assignment 9

section .data
msg1 db "Factorial Of Given Number : "
len1 equ $-msg1 msg2 db "Given Number : " len2 equ$-msg2
msg0 db "Factorial of 0 : 1",10
len0 equ $-msg0
newline db 10,13
factorial dd 1

section .bss
final resb 8
result resb 4
counter resb 4
num resb 4
numh resb 4
numlen resb 4

%macro print 2
mov eax, 4
mov ebx, 1
mov ecx, %1
mov edx, %2
int 0x80
%endmacro

%macro read 2
mov eax, 3
mov ebx, 0
mov ecx, %1
mov edx, %2
int 0x80
%endmacro

section .text
global _start
_start:
xor eax, eax
mov dword[num], eax
print msg2,len2
pop ecx
pop ecx
pop ecx
mov edx, 00
up:
cmp byte[ecx + edx], 0
jz l1
inc edx
jmp up
l1:
mov esi, ecx
mov eax, dword[esi]
mov dword[num],eax
mov dword[numlen], edx
print num,dword[numlen]
print newline, 1

		mov esi, num
		call packnum		;convert ascii to hex
		mov dword[numh], ebx
		cmp dword[numh], 0
		jne next2
		print msg0, len0
		jmp exit
		
	next2:
		mov ecx, dword[numh]
		call facto
		mov edx, dword[factorial]
		mov dword[result],edx
		call ascii
		print msg1, len1
		print final, 8
		print newline, 1
		
	exit:
		mov eax, 1
		mov ebx, 0
		int 0x80
		
	packnum:
		mov eax, 0
		mov ecx, dword[numlen]
		mov dword[counter],ecx
		mov ebx, 0
		back:
			mov al, [esi]
			rol ebx, 4
			cmp al, 39h
			jbe next
			sub al, 7h
		next:
			sub al,30h
			or bl, al
			inc esi
			dec dword[counter]
			jnz back
		ret
		
	ascii:
		mov esi, final
		mov dword[counter], 8
		mov eax, dword[result]
		bck2:
			mov ebx, eax
			rol ebx, 04
			mov eax, ebx
			and bl, 0fh
			cmp bl, 9h
			jbe next1
			add bl, 7h
		next1:
			add bl, 30h
			mov [esi], ebx
			inc esi
			dec dword[counter]
			jnz bck2
		ret
		
	facto:
		push ecx
		cmp ecx, 01
		jne next3
		jmp exit1
		next3:
			dec ecx
			call facto
		exit1:
			pop ecx
			mov eax, ecx
			mul dword[factorial]
			mov dword[factorial], eax
		ret