extern  printf

SECTION .data

    p1_fmt: db  0xA,`\nOutput: %d\n`, 0xA, 0

SECTION .text

    global main

main:
;-------------------------------------------------------------------------------------------------------------------
fibonacci:
    push    ebp     ;Build Stack Frame(?)
    mov ebp, esp
    sub esp, 16

    mov eax, [ebp+8];   ;what is this, and what does it do?
    cmp eax, 2
    jae recur

    xor edx, edx    ;Set contents of edx to zero, why?
    jmp done
;-------------------------------------------------------------------------------------------------------------------
recur:
    sub eax, 2
    push    eax     ; compute fib(n-2)
    call    fibonacci
    mov [ebp-8], eax    ; save returned value in 8-byte local variable...
    mov [ebp-4], edx    ; ...in Little-Endian byte order.

    mov eax, [ebp+8]    ; get argument again
    dec eax
    push    eax     ; compute fib(n-1)
    call    fibonacci
    mov [ebp-16], eax   ; save returned value in 8-byte local variable...
    mov [ebp-12], edx   ; ...in Little-Endian byte order.

    mov eax, [ebp-8]
    mov edx, [ebp-4]    ; retrieve 1st computed value
    add eax, [ebp-16]
    adc edx, [ebp-12]   ; add 2nd computed value
;-------------------------------------------------------------------------------------------------------------------
done:
    pop edx
    push    edx
    push    p1_fmt      ;push address of format string
    call    printf      ;Call C function
    add esp, 12     ;adjust ESP to remove parameter

    mov esp, ebp
    pop ebp
    ret         ;return