Factorial in assembly

fact.asm

section .text
global _fact

_fact:
mov ecx, [esp+4]
mov eax,1
jmp for


for:
mul ecx
dec ecx
jnz for
ret

factorial.c

#include <stdio.h>
#include <conio.h>
int __cdecl fact(int);
int main(){
int num=10;
printf("%d", fact(num));
_getch();
return 0;
}