APPENDIX FIVE _____________________________________________________________



Color

Color is a very important aspect in the Atari computers; you may not
fully appreciate it unless you've spent a long time working with
computers or monitors with monochrome displays. The Atari has
sixteen colors available for display in eight different luminance
(brightness) factors. These colors are stored in memory locations 704
to 712. The first four of these registers are used to determine the color
of your players and missiles. The second five determine the color of the
playfields, background, lines drawn and areas filled.

The Atari has a default value for each of the five playfield registers that
is assigned on powerup:

Playfield   Location  Color            Value
0           708       Orange             40
1           709       Light green       202
2           710       Dark blue         148
3           711       Red                70
4 (BAK)     712       Black               0

The figure in the value category represents the number you would get
if you PEEKed into that location. For discussion of the locations, refer
to the Memory Map.

To change these colors, you can use either a POKE statement or the
BASIC command SETCOLOR (abbreviated to SE). You should refer to
the description in the earlier Memory Map text. SETCOLOR has three
parameters: the register to change (which always corresponds to one
of the memory locations above); the hue (a number from zero to fifteen
which corresponds to the available colors); and the luminance (an
even number between zero and fourteen). The Atari will treat any odd
number as if it were the next lowest even number where luminance is
concerned. Your statement might look like this:

SETCOLOR 0,2,8

This will produce the orange color in playfield zero. To change it to
red, you would use:

SETCOLOR 0,4,6

Unless you are changing the background or border or you are
changing a register which has already been used for drawing on the
screen, you won't see any change from using SETCOLOR. The effect
comes when you follow up with a COLOR command, telling the Atari
which register to use for the DRAWTO or fill command. You can easily
POKE the location with the proper color value by using this formula:

COLOR = HUE * 16 + LUMINANCE

So the orange in the above example would be obtained by: