name "vga"

; this program draws a tiny rectangle in vga mode. 

org  100h

jmp code

; dimensions of the rectangle: 
; width: 10 pixels 
; height: 5 pixels 

w equ 10
h equ 5


; set video mode 13h - 320x200 

code:   mov ah, 0
        mov al, 13h
        int 10h


; draw upper line: 

    mov cx, 100+w  ; column 
    mov dx, 20     ; row 
    mov al, 15     ; white 
u1: mov ah, 0ch    ; put pixel 
    int 10h

    dec cx
    cmp cx, 100
    jae u1

; draw bottom line: 

    mov cx, 100+w  ; column 
    mov dx, 20+h   ; row 
    mov al, 15     ; white 
u2: mov ah, 0ch    ; put pixel 
    int 10h

    dec cx
    cmp cx, 100
    ja u2

; draw left line: 

    mov cx, 100    ; column 
    mov dx, 20+h   ; row 
    mov al, 15     ; white 
u3: mov ah, 0ch    ; put pixel 
    int 10h

    dec dx
    cmp dx, 20
    ja u3


; draw right line: 

    mov cx, 100+w  ; column 
    mov dx, 20+h   ; row 
    mov al, 15     ; white 
u4: mov ah, 0ch    ; put pixel 
    int 10h

    dec dx
    cmp dx, 20
    ja u4


; pause the screen for dos compatibility: 

;wait for keypress 
  mov ah,00
  int 16h

; return to text mode: 
  mov ah,00
  mov al,03 ;text mode 3 
  int 10h



ret