Bouncing Ball

title Bouncing Ball										(bounce.asm)

; Dani Horowitz
; CSC111 x86 Assembly Programming

; This program displays a bouncing ball on the screen

INCLUDE Irvine32.inc

;--------------------------------------------------
.stack			; begin stack segment

;--------------------------------------------------
.data			; begin data segment

	ball			byte	'O'			; ball character
	row				byte	10			; starting vertical location of ball
	column			byte	30			; starting horizontal location of ball
	xvector			byte	1			; direction of X vector (1=right, 0=left)
	yvector			byte	1			; direction of Y vector (1=down, 0=up)
;--------------------------------------------------
.code			; begin code segment

;--------------------------------------------------
;--------------------------------------------------
flipx PROC
;
; Flips X vector if necessary
;--------------------------------------------------
	cmp		column, 70		; did we reach right boundary?
	jge		FlipLeft		; if yes then goto FlipLeft
	cmp		column, 0		; did we reach left boundary?
	jle		FlipRight		; if yes then goto FlipRight
	jmp		Done

FlipLeft:					; set X vector left
	mov		xvector,-1
	jmp		Done
	
FlipRight:					; set X vector right
	mov		xvector,1
	
Done:
	ret
;--------------------------------------------------
flipx ENDP
;--------------------------------------------------


;--------------------------------------------------
;--------------------------------------------------
flipy PROC
;
; Flips Y vector if necessary
;--------------------------------------------------
	cmp		row, 30			; did we reach bottom boundary?
	jge		FlipUp			; if yes then goto FlipUp
	cmp		row, 0			; did we reach top boundary?
	jle		FlipDown		; if yes then goto FlipDown
	jmp		Done

FlipUp:						; set Y vector up
	mov		yvector,-1
	jmp		Done
	
FlipDown:					; set Y vector down
	mov		yvector,1
	
Done:
	ret
;--------------------------------------------------
flipy ENDP
;--------------------------------------------------


;--------------------------------------------------
eraseball PROC
;
; Positions the cursor at the correct screen coordinates
; and then draws an empty string
;--------------------------------------------------
	mov		dh, row
	mov		dl, column
	call	Gotoxy			; goto row,column coordinates
	mov		al, ' '
	call	WriteChar		; print empty string
	ret
;--------------------------------------------------
eraseball ENDP
;--------------------------------------------------


;--------------------------------------------------
drawball PROC
;
; Positions the cursor at the correct screen coordinates
; and then draws a ball
;--------------------------------------------------
	mov		dh, row
	mov		dl, column
	call	Gotoxy			; goto row,column coordinates
	mov		al, ball
	call	WriteChar		; print ball to screen
	ret
;--------------------------------------------------
drawball ENDP
;--------------------------------------------------


;--------------------------------------------------
moveball PROC
;
; Determines new coordinates for ball
; Updates row and column values
;--------------------------------------------------

TestHorizontal:
	call	flipx			; flip xvector if necessary
	cmp		xvector,1		; is xvector set to right?
	je		GoRight			; if yes goto GoRight
	jmp		GoLeft			; goto GoLeft
	
TestVertical:
	call	flipy			; flip y vector if necessary
	cmp		yvector,1		; is yvector set to down?
	je		GoDown			; if yes goto GoDown
	jmp		GoUp			; goto GoUp
	
GoRight:
	inc		column			; move right
	jmp		TestVertical	; prepare to move up or down

GoLeft:
	dec		column			; move left
	jmp		TestVertical	; prepare to move up or down

GoDown:	
	inc		row				; move down
	jmp		Done

GoUp:
	dec		row				; move up

Done:
	
	ret
;--------------------------------------------------
moveball ENDP
;--------------------------------------------------


;--------------------------------------------------
take5 PROC
;
; Take a break! Pauses screen
;--------------------------------------------------
	mov		eax,100
	call	Delay
	ret
;--------------------------------------------------
take5 ENDP
;--------------------------------------------------


;--------------------------------------------------
main proc
;--------------------------------------------------
	call	Clrscr			; clear screen
BounceBall:
	call	drawball		; draw ball to the screen
	call	take5			; pause
	call	eraseball		; erase ball from current location
	call	moveball		; determine new coordinates for ball
	jmp		BounceBall		; loop
	
EndBounce:
	exit
	
main  endp
end main
;--------------------------------------------------