factorial_no_recursion.asm

default rel
bits 64

segment .data
    fmt db "%d", 0xd, 0xa, 0

segment .text

global main
global factorial

extern _CRT_INIT
extern ExitProcess
extern printf


factorial:
    push    rbp
    mov     rbp, rsp
    sub     rsp, 32

    test    ecx, ecx    ; n
    jz     .zero

    mov    ebx, 1       ; counter c
    mov    eax, 1       ; result

    inc    ecx

.for_loop:
    cmp    ebx, ecx
    je    .end_loop

    mul    ebx          ; multiply ebx * eax and store in eax

    inc    ebx          ; ++c
    jmp    .for_loop

.zero:
    mov    eax, 1

.end_loop:
    leave
    ret


main:
    push    rbp
    mov     rbp, rsp
    sub     rsp, 32

    mov     rcx, 5
    call    factorial

    lea     rcx, [fmt]
    mov     rdx, rax
    call    printf

    xor     rax, rax
    call    ExitProcess