global factorial
section .text

; Input in ECX register
; Output in EAX register
factorial:
  mov   eax, 1  ; default argument, store 1 in accumulator

.base_case:
  test  ecx, ecx
  jnz   .inductive_case  ; return accumulator if n == 0
  ret

.inductive_case:
  mul   ecx         ; accumulator *= n
  dec   ecx         ; n -= 1
  jmp   .base_case  ; tail call