cs401 assignment 3 solution fall 2019 2020

Question:

Suppose we want to draw a square on our computer screen as shown below.

name “vga”

; this program draws a square in vga mode.

org  100h

jmp code

; dimensions of the square:

; width:  50 pixels

; height: 50 pixels

w equ 50

h equ 50

; set video mode 13h – 320×200

code:   mov ah, 0

mov al, 13h

int 10h

; draw upper line:

mov cx, 100+w  ; column

mov dx, 20     ; row

mov al, 0010     ; green

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, 0001     ; blue

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, 35      ; pink

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, 20    ; gray

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