182 The VIC 20
User
Guide
location you are POKEing
is
correctly set. The next section describes how to
do
this.
Color
Memory
Earlier in this chapter
we
mentioned
that
the colors
of
the characters
on
the screen are kept in a special area called color memory. As
our
most recent
example shows,
an
understanding
of
how
to
use color memory
is
essential
when using
POKE
in displays. So, before proceeding further with POKEing
screen memory, let's take a look
at
color memory.
FINDING
COLOR
MEMORY
Like screen memory, color memory "moves,"
but
the factors
that
determine its location are different.
To
find the start
of
color memory, use
the following formula:
10
CB=37888+256*(PEEK(648)
AND
2)
The section entitled
"VIC
Chip's Window into Memory" near the end
ofthis chapter includes more information
on
how the VIC chip locates color
memory.
CONTENTS
OF
COLOR
MEMORY
As with screen memory, there
is
one location in color memory for each
character
on
the screen. The order
of
character colors
is
the same as
that
of
the characters themselves, so the formula used
to
find a character's location
in color memory
is
like the one used
to
locate the character in screen
memory.
Color memory location = start of color memory + column +
22
• row
The color
of
each character
is
stored in color memory as a number from
o to
7.
The colors produced by these numbers are as follows:
o Black
White
2 Red
3 Cyan
4 Purple
5 Green
6 Blue
7 Yellow
To help you remember these numbers, you can use the following rule:
fhe
POKE
value
to
set a color
is
one less
than
the value
of
the number key
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