Commodore Plus 4 - Page 106

50 FOR L = 0 TO 359 STEP A
60 BOX 1, 100, 30, 220, 130, L
70 NEXT L
80FORL-1 TO 2000: NEXT L
90 GRAPHIC 0,1
5 TRAP 60
10 GRAPHIC 2,1
20DEFFNA(X)=-- INT(RND(1)' X)
30 COLOR 1, FNA(15) + 1
40 BOX 1, FNA(320). FNA(160), FNA(320), FNA(160),, 1
50 GOTO 30
60
COLOR 1,2,3: GRAPHIC 0
Hi; return and type RUN after each program is completely en
tered Hold down the STOP key to end the program.
The second program draws different colored squares all over the
screen. You'll notice some parts of the screen changing when other
parts near them change. The reason for this was discussed earlier in
this chapter.
Drawing Your Plus'4 also has commands (or drawing circles. Like the BOX
Circles C0!r'mand. we can vary tne shape of the circle to form an oval (also
called an ellipse), and we can rotate the oval. We can also just draw
a section of the shape (called an arc)
This command draws a circle in the center of the screen: CIRCLE
1.160,100.50. This tells the Plus/4 to draw a circle with its center at row
160 and column 100, with a radius of 50. This actually produces an
oval, since the dots on the screen are taller than they are wide. To
change this to a real circle you must add a separate number to tell that
the height is different from the width, like this CIRCLE 1.160.100,50,42
The Plus/4 can also draw a square, triangle or other polygon using the
CIRCLE command. Just tell the computer how many degrees to go
between points on the circle, like this CIRCLE 1.160.100,50.42....120
This command draws a triangle, since each side is 120 degrees
(Omitting number values while including commas in a graphic com
mand causes the computer to read standard default values for the
missing number.) A simple formula to get the angle for a polygon with
N sides is 360/N.
Here's a quick program for drawing polygons