[Assembly] 어셈블리어 팩토리얼 소스코드 구현하기

[ 하루 일 어셈블리 코딩 ]

nasm intel 32bit assembly

descriptor : factorial을 구현해보자

 
%isdnclude "asm_io.inc"
 
segment .bss
    number resd 1
 
segment .data
    outmsg1 db "input your number : ", 0
    format1 db "%s", 0
    format2 db "%d", 0
 
segment .text
    extern printf
    extern scanf
    global main
    global factorial
 
main:
    push ebp
    mov ebp, esp
    push outmsg1
    push format1
    call printf
    add esp, 8
 
    push number
    push format2
    call scanf
    add esp, 8
 
    xor eax, eax
    push dword [number]
    call factorial ;factorial함수 호출 
    add esp, 4
 
    push eax
    push format2
    call printf
    add esp,8
    call print_nl ;개행 
    pop ebp
    ret
 
factorial:
    push ebp
    mov ebp, esp
    cmp dword [ebp+8], 0 ;input값이 0일시 
    je end    
    mov ebx, [ebp+8]
    sub ebx, 1 ;n-1 
    push ebx
    call factorial ;다시 호출 
    add esp, 4    
    imul eax, [ebp+8] ;return f(n-1) * n 
 
    pop ebp
    ret
 
end:
    mov eax, 1 
    pop ebp
    ret