Chapter
6:
Graphics 201
reusing it with screen editing
to
avoid rolling the sample characters off the
top
of
the screen.
POKE
7168,56
POKE
716!M!6
POKE
7170,16
POKE
7171,124
POKE;
7172,16
POKE
7173,16
POKE
7175,40
As each
PO
KE
is
entered, one row
of
the @ character
is
changed until the @
sign
is
replaced with
our
stick man. Now, type CTRL-RVS ON, then
@;
the
VIC will display a stick mail. Press the
CRSR LEFT key until the cursor
is
over
the stick man. Instead
of
changing back
and
forth between reversed and
nonreversed
@ signs, the character changes from @ to
our
stick man and
back.
Now you're ready
to
experiment with characters
of
your own design.
Simply follow the steps
we
outlined above: POKE the values you calculated
on the worksheet into character memory, and use
CTRL-RVS
ON
to make the
VI C display your character from the reversed portion
of
character memory.
We recommend
that
you experiment with several characters before putting
them to work in programs.
Design
Aids
for
Custom
Characters
If
you expect
to
make extensive use
of
custom characters, you will find
it helpful
to
have a character editor utility to help you. Such a program
should display the character in
both
normal and magnified views, allow you
to change individual dots, and calculate the POKE values and locations for
you. You can write your own utility
or
you can purchase one, such as
Commodore's "Programmable Character Set and Game Graphics Editor."
If
you wish to write your own utility, several parts
of
the program can
be taken from the examples in Chapters 5
and
6
of
this book. The Character
Magnifier program
in
this chapter can be used
to
display the character, and
the Moving
Dot
program can be used as a base for the subroutine to change
the dots. (Hint: Use a delay loop to flash the magnified
dot
off and on, and
use the Fire button on the joystick to change the dots.)
If
you plan to use custom characters only occasionally, using the
worksheet to
layout
your characters and calculating the POKE values by
hand should be sufficient.
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