TITLE Cartesian Coordinates                 (Pixel2.asm)

; This program switches into 800 X 600 graphics mode and
; draws the X and Y axes of a Cartesian coordinate system.
; Switch to full-screen mode before running this program.
; Color constants are defined in Irvine16.inc.
; Last update: 12/14/01

INCLUDE Irvine16.inc

Mode_6A = 6Ah		; 800 X 600, 16 colors
X_axisY = 240    ;300
X_axisX = 10
X_axisLen = 600;;;700

Y_axisX = 320    ;;;400
Y_axisY = 10
Y_axisLen = 600;;;540

.data
saveMode BYTE ?
currY WORD ?
currX WORD ?
.code
main PROC
	mov ax,@data
	mov ds,ax

; Save the current video mode
	mov  ah,0Fh	; get video mode
	int  10h
	mov  saveMode,al

; Switch to a graphics mode
	mov  ah,0   	; set video mode
	mov  al,12h;;;Mode_6A	; 800 X 600, 16 colors
	int  10h

; Draw the X-axis
	mov  cx,X_axisX	; X-coord of start of line
	mov  dx,X_axisY	; Y-coord of start of line
	mov  ax,X_axisLen 	; length of line
	mov  bl,white	; line color (see IRVINE16.inc)
	call DrawHorizLine	; draw the line now

; Draw the Y-axis
	mov  cx,Y_axisX	; X-coord of start of line
	mov  dx,Y_axisY	; Y-coord of start of line
	mov  ax,Y_axisLen	; length of line
	mov  bl,white	; line color
	call DrawVerticalLine	; draw the line now
;draw a line
mov cx,y_axisX
mov dx,x_axisY
mov ax,200
mov bl,red
mov si,3
mov di,1
call DrawALine
mov cx,y_axisX
mov dx,x_axisY
mov ax,200
mov bl,red
mov si,-3
mov di,-1
call DrawALine
; Wait for a keystroke
	mov  ah,10h	; wait for key
	int  16h

; Restore the starting video mode
	mov  ah,0   	; set video mode
	mov  al,saveMode   	; saved video mode
	int  10h

	exit
main endp
;------------------------------------------------------
DrawHorizLine PROC
;
; Draws a horizontal line starting at position X,Y with
; a given length and color.
; Receives: CX = X-coordinate, DX = Y-coordinate,
;           AX = length, and BL = color
; Returns: nothing
;------------------------------------------------------



.code
	pusha
	mov  currX,cx	; save X-coordinate
	mov  cx,ax	; loop counter

DHL1:
	push cx	; save loop counter
	mov  al,bl	; color
	mov  ah,0Ch	; draw pixel
	mov  bh,0	; video page
	mov  cx,currX	; retrieve X-coordinate
	int  10h
	inc  currX	; move 1 pixel to the right
	pop  cx	; restore loop counter
	Loop DHL1

	popa
	ret
DrawHorizLine ENDP

;------------------------------------------------------
DrawALine PROC
;
; Draws a  line starting at position X,Y with
; a given length and color.
; Receives: CX = X-coordinate, DX = Y-coordinate,
;           AX = length, and BL = color
;di=xinc   si=yinc
; Returns: nothing
;------------------------------------------------------


	pusha
	mov  currX,cx	; save X-coordinate
	mov  cx,ax	; loop counter

DHL1:
	push cx	; save loop counter
	mov  al,bl	; color
	mov  ah,0Ch	; draw pixel
	mov  bh,0	; video page
	mov  cx,currX	; retrieve coordinates
	int  10h
	add currx,di
	add dx,si
	pop  cx	; restore loop counter
	Loop DHL1

	popa
	ret
DrawALine ENDP

;------------------------------------------------------
DrawVerticalLine PROC
;
; Draws a vertical line starting at position X,Y with
; a given length and color.
; Receives: CX = X-coordinate, DX = Y-coordinate,
;           AX = length, BL = color
; Returns: nothing
;------------------------------------------------------


	pusha
	mov  currY,dx	; save Y-coordinate
	mov  currX,cx	; save X-coordinate
	mov  cx,ax	; loop counter

DVL1:
	push cx	; save loop counter
	mov  al,bl	; color
	mov  ah,0Ch	; function: draw pixel
	mov  bh,0	; set video page
	mov  cx,currX	; set X-coordinate
	mov  dx,currY	; set Y-coordinate
	int  10h	; draw the pixel
	inc  currY	; move down 1 pixel
	pop  cx	; restore loop counter
	Loop DVL1

	popa
	ret
DrawVerticalLine ENDP
END main