%define COUNT   20
[bits   16]
[org    0x7c00]
start:
    cli
    xor ax, ax
    mov ds, ax
    mov es, ax
    mov ss, ax
    mov ax, 0x9c00
    mov sp, ax
    mov cx, COUNT
    sti
fizzbuzz:
    .printnumber:
        mov ax, cx
        call    putword
    .test3:
        mov ax, cx
        mov dh, 3
        div dh
        or  ah, ah
        jz  .fizz
    .test5:
        mov ax, cx
        mov dh, 5
        div dh
        or  ah, ah
        jz  .buzz
        jmp .testcx
    .fizz:
        mov si, fizz
        call    putstr
        jmp .test5
    .buzz:
        mov si, buzz
        call    putstr
    .testcx:
        mov si, crlf
        call    putstr
        or  cx, cx
        jz  hang
        dec cx
        jmp fizzbuzz
hang:
    cli
    hlt
    jmp $
putchar:
    mov ah, 0x0e
    int 0x10
    ret
putstr:
    .do_char:
        lodsb
        or  al, al
        jz  .done
        call    putchar
        jmp .do_char
    .done:
        ret
putnibble:
    cmp al, 10
    jl  .lt10
    add al, 'A' - 10
    call    putchar
    jmp .done
    .lt10:
        add al, '0'
        call    putchar
    .done:
        ret
putbyte:
    push    ax
    shr al, 4
    call    putnibble
    pop ax
    and al, 0x0f
    call    putnibble
    cmp bx, 0
    je  .done
    mov al, ' '
    call    putchar
    .done:
        ret
putword:
    push    bx
    push    ax
    mov al, ah
    mov bx, 0
    call    putbyte
    pop ax
    mov bx, 0
    call    putbyte
    mov al, ' '
    call    putchar
    pop bx
    ret
fizz:           db  "fizz", 0
buzz:           db  "buzz", 0
crlf:           db  13, 10, 0
times 510 - ($ - $$)    db  0
            dw  0xaa55