Variables with Graphics

The previous program did arithmetic as part of a graphics statement. You can use variables with graphics statements as well. Here is a program to draw four circles at the center of the screen, but this time done with variables:

' Draw four circles at the center of the screen
SCREEN 12
'
LET CENTERX = 640 / 2
LET CENTERY = 480 / 2
LET RADIUS = 25
'
COLOR 4
CIRCLE  (CENTERX, CENTERY), RADIUS
'
COLOR 8
CIRCLE  (CENTERX, CENTERY), RADIUS * 2
'
COLOR 9
CIRCLE  (CENTERX, CENTERY), RADIUS * 3
'
COLOR 10
CIRCLE  (CENTERX, CENTERY), RADIUS * 4
END

This new program does same thing as the previous version. But by using variables it is more clear what it does, and the program is more easily modified.