Chapter 8
Not too shabby for rank amateurs.
Here’s what happens:
Line 10 clears the screen.
Line 20 selects the “low memory”
HIRES page. This part of memory is
used for high-resolution graphics, while text is stored on a different ‘page’
of memory.
48K disk users have two different chunks of memory that can be used for
HIRES graphics. If we wanted, we could store 2 different pictures at the
same time. Refer to the Apple Programming Reference Manual for more
information.
Line 30 selects a color.
Lines 40 and 70 set up a loop for plotting a figure.
Line 50 calculates the radius as a function of the angle. We are using polar
coordinates in case you hadn’t guessed. If you don’t really care, it doesn’t
really matter - the picture is still pretty.
Line 60 converts from polar to rectangular coordinates and plots a single
point. Whew! It’s a good thing computers don’t require a good math
background.
Why All This Math?
Using Math equations to create graphics is easier than by doing it the hard way,
point-by-point. They do, however, restrict us to graphs or plots of natural
phenomena, and who among us will claim credit for creativity in that area‘?
Type:
TEXT
to return back to the TEXT page. Even though we can’t see it, the picture
remains stored in the HI-RES page of memory.
We can play with line 50 to get different figures. Try:
50 R=3 * A
and
72
