; common.inc -- tiny output helpers shared by the demo programs (DOS .COM, NASM syntax)

; print the '$'-terminated string at DS:DX  (INT 21h, AH=09h)
puts:
    mov ah, 09h
    int 21h
    ret

; print CRLF
crlf:
    mov dx, s_crlf
    jmp puts
s_crlf db 0Dh, 0Ah, '$'

; print AX as four hex digits using INT 21h AH=02h
puthex16:
    push ax
    mov al, ah
    call puthex8
    pop ax
puthex8:
    push ax
    shr al, 1
    shr al, 1
    shr al, 1
    shr al, 1
    call nib
    pop ax
    and al, 0Fh
nib:
    add al, '0'
    cmp al, '9'
    jbe .ok
    add al, 7
.ok:
    mov dl, al
    mov ah, 02h
    int 21h
    ret

; print AX as unsigned decimal
putdec:
    push bx
    push cx
    push dx
    xor cx, cx
    mov bx, 10
.d1:
    xor dx, dx
    div bx
    push dx
    inc cx
    test ax, ax
    jnz .d1
.d2:
    pop dx
    add dl, '0'
    mov ah, 02h
    int 21h
    loop .d2
    pop dx
    pop cx
    pop bx
    ret