Silly Circles

Mike Aston


Issue 2

Feb/Mar 83

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Explore the Atari Display Lists with this shape changing program. Here's how it works.

LINE 10 - establishes a standard display list for mode 7.

LINES 20 to 60 - draw a circle.

LINE 100 - sets the pointer to the display list.

LINES 150 to 250 - change the display list a line at a time from the standard 4 colour mode with 96 vertical rows to a 4 colour mode with 192 vertical rows on a full screen. This effectively halves the height of the circle producing an elliptical shape.

Try changing LINE 150 to Z=-1, or Z=-2. or Z=-3.

Add more colours to the circle or change the original shape. You could also try starting off in a different graphics mode but don't forget to make LINE 10 specify the mode with the largest RAM requirement that you are going to use.

AtariLister - requires Java