DaniWeb IT Discussion Community

Code Snippets (http://www.daniweb.com/code/)
-   asm (http://www.daniweb.com/code/asm.html)
-   -   Text Mode Bouncing Ball (http://www.daniweb.com/code/snippet850.html)

bad_dreams99 asm syntax
Apr 19th, 2008
This is a very simple program that uses text mode to display a boucing "ball." The ball is just a character that moves across the screen, erasing all in its path. It is coded to work like a screensaver, so the program ends when any key is hit.

NOTE: I am in no ways an assembly guru, if anything i'm a noob; however, if this code helps someone out, then thats great.

This could be good framework for coding in graphics mode. Just replace the ball character with a bit pattern. Anyways, enjoi.
 

  1. page 60,132
  2. ;--------------------------------------------------------------------------
  3. ; Name: Nathan Gallagher
  4. ; Description:  Creates a character (ball) that moves accross the screen, acts as a screensaver
  5. ;		    will end when a key is pressed
  6. ;--------------------------------------------------------------------------
  7.  
  8.  
  9.  
  10. ;-----------------------------------------------------------------------
  11. ;stack segment
  12.  
  13. sseg      segment para stack 'stack'
  14.           db   120 dup(?)    ;reserve 120 bytes for the stack
  15. sseg      ends
  16.  
  17. ;-----------------------------------------------------------------------
  18. ;constants
  19.  
  20.  
  21.  
  22. ;-----------------------------------------------------------------------
  23. ;data segment
  24.  
  25. dseg      segment para 'data'
  26.  
  27.           ball db 'O'		;create ball character
  28. 		  x db 01h			;create the x-coordinate variable
  29. 		  y db 01h			;create the y-coordinate variable
  30. 		  incX db 01h		;create the variable that moves x
  31. 		  incY db 01h		;create the cariable that moves y
  32. 		  eraser db ' '		;create an erasor to clear the ball character
  33.  
  34.  
  35. dseg      ends
  36.  
  37. ;----------------------------------------------------------------------
  38. ;code segment
  39. cseg      segment para 'code'
  40.  
  41. main      proc far               ;this is the program entry point
  42.           assume cs:cseg, ds:dseg, ss:sseg 
  43.           mov  ax,dseg           ;load the data segment value
  44.           mov  ds,ax             ;assign value to ds
  45.  
  46. 		call cursor		;Set up initial cursor
  47. 		;this runs until user hits the keyboard
  48. start:	mov dl,incX
  49. 			add dl,x
  50. 			mov x,dl		;increment X
  51. 		mov dl,incY
  52. 			add dl,y
  53. 			mov y,dl		;increment Y
  54. 		call cursor			;set up our cursor
  55. 		;see if we need to swap anything			
  56. 		call swapX				;swap our X inc value if needed
  57. 		call swapY				;swap our Y inc value if needed
  58.  
  59. 		;time to draw our ball!		
  60. 		mov dl,ball
  61. 		mov ah,2h		
  62. 		int 21h				;output the ball
  63. 		;delay
  64. 		call wait		
  65. 		;erase ball
  66. 		call cursor
  67. 		mov dl,eraser		;erase the ball
  68. 		mov ah,2h
  69. 		int 21h
  70.  
  71. keyboard:         mov ah,1		;loop at end to display results		 
  72. 		  int	16H
  73. 		  jnz	quit		;if a key is pressed, hit the bricks!
  74. 		  jmp start		 	;jump to start if key isnt hit
  75.  
  76. quit:     call cls				;clear screen before returning to DOS
  77. 		  mov  ah,4Ch            ;set up interupt
  78.           int  21h               ;Interupt to return to DOS
  79. main      endp
  80.  
  81. ;----------------------------------------------
  82. ; Delay process
  83. ;runs through multiple loops to make the wait more potent
  84. ;----------------------------------------------
  85. wait proc		
  86. 		mov cx,12000d
  87. delay1:	in al,61h
  88. 		and al,10h
  89. 		cmp al,ah		
  90. 		je wait
  91. 		mov ah,al
  92. 		loop delay1
  93.  
  94. 		mov cx,12000d
  95. delay2:	in al,61h
  96. 		and al,10h
  97. 		cmp al,ah		
  98. 		je wait
  99. 		mov ah,al
  100. 		loop delay2
  101.  
  102. 		mov cx,12000d
  103. delay3:	in al,61h
  104. 		and al,10h
  105. 		cmp al,ah		
  106. 		je wait
  107. 		mov ah,al
  108. 		loop delay3
  109.  
  110. 		mov cx,12000d
  111. delay4:	in al,61h
  112. 		and al,10h
  113. 		cmp al,ah		
  114. 		je wait
  115. 		mov ah,al
  116. 		loop delay4
  117.  
  118. 		mov cx,12000d
  119. delay5:	in al,61h
  120. 		and al,10h
  121. 		cmp al,ah		
  122. 		je wait
  123. 		mov ah,al
  124. 		loop delay5
  125. 		ret
  126. wait endp
  127. ;----------------------------------------------
  128. ;----------------------------------------------------------------------
  129. ;here's a procedure that sets the cursor
  130. ;----------------------------------------------------------------------
  131. cursor  proc
  132. 		 mov ah,02		;load sub function for int
  133. 		 mov bh,00		;sets page 0
  134. 		 mov dl,x		;sets the column based on x
  135. 		 mov dh,y		;sets the row based on y
  136. 		 int 10h		;calls interupt
  137. 		 ret
  138. cursor	endp
  139. ;----------------------------------------------------------------------
  140.  
  141.  
  142. ;Loops for changing incX and incY ------------------------------------------------------------------
  143. swapX proc
  144. 		cmp x,79d
  145. 		jge goLeft			;if x is at the limit, jump
  146. 		cmp x,0d
  147. 		jle goRight			;if x is at the limit, jump
  148. 		jmp Xbottom
  149.  
  150. goLeft:	mov incX,-1			;make the ball go left
  151. 		jmp Xbottom
  152.  
  153. goRight: mov incX,1			;make the ball go right
  154. 		 jmp Xbottom
  155.  
  156. Xbottom:	nop
  157. 		ret		 
  158. swapX endp
  159. ;---------------------------------------------------------------------------
  160. swapY proc
  161. 		cmp y,25d			;if y is at the limit, jump
  162. 		jge goUp
  163. 		cmp y,0d
  164. 		jle goDown			;if y is at the limit, jump
  165. 		jmp yBottom
  166.  
  167. goUp:	mov incY,-1			;make the ball go up
  168. 		jmp yBottom
  169.  
  170. goDown:  mov incY,1			;make the ballgo down
  171. 		 jmp yBottom
  172.  
  173. yBottom: nop	
  174. 		ret	
  175.  
  176. swapY endp
  177. ;---------------------------------------------------------------------------
  178. ;----------------------------------------------------------------------
  179. ; Here is a procedure that clears the screen
  180. ;----------------------------------------------------------------------
  181. cls		 proc
  182. 		 mov ax,0600h	;scroll screen
  183. 		 mov bh,07		;normal attribute
  184. 		 mov cx,0000	;start at 00,00
  185. 		 mov dx,184fh	;end at 24,79
  186. 		 int 10h		;call int 10
  187. 		 ret
  188. cls		 endp
  189. ;---------------------------------------------------------------------		
  190.  
  191. cseg      ends
  192.           end     main           ;Program exit point