Texas Instruments TI-99/4A - Page 176

Bouncing Ball
This program moves a ball and bounces it off the edges of the
screen. Each time the ball hits any side, a tone sounds. and the ball
is d~flected. The following special character is used to define the
ball.
Block
Codes
Examples:
x
X
X
X
X
X
X
X X
X
X X
X
X
X X X
X
X X
X
X
X
X X
X
X X
X X X X X
X
X
X
X
X
X X X
X
X
X
X
X X X
X
X
X X
3C
7E
FF
FF
FF
FF
7E
3C
:>NEW
These statements clear the SCreen and define character 96 as the
ball.
These statements allow you to input the color of the ball and the
screen background color. N ate that defining the screen color by
using character set 1. which includes character 32 (the blank
space), gives definite limits for the screen edge. The screen is
cleared
when the colors have been entered.
These statements give the starting position for the ball and set the
parameters which will control the X and Y direction.
These statements compute the next ball position. The direction the
ball moves
depends on the current values 01 XDIR (+ 1 indicates
right,
-1 indicates left) and YOIR (+ 1 indicates up. -1 indicates
down).
These statements test to see if the new ball position is still on the
screen.
If either the row (Y) or column (X) value is out of range,
then the program transfers to line 310 (eolumn out of range) or line
360 (row out of range} to change the ball direction.
111-20
>100 REM BOUNCING BALL
>110 O.LL CLEAR
>120 CALL CHAR(96,"3C7EFFFFFF
FF7E3C"}
>130
INPUT "BALL COLOR? ":C
>140 INPUT "SCREEN COLOR? ":S
>150 CALL CLEAR
>160 CALL COLOR(9,c,S)
>170 CALL COLOR(1,S,S)
>180 X"'16
>190 Y"'12
>200 XDIR"'1
>210 VOIR=1
>220 X=X+XDIR
>230 V~V+VDIR
>240 IF X<1 THEN 310
>250 IF X>32 THEN 310
>260 IF Y<1 THEN 360
>270 IF Y>24 THEN 360
User's Reference Guide