178
The VIC 20 User
Guide
In
step 2, after clearing the screen, type RVS ON (CTRL-9),
SHIFT-£,
and
C::-*
.
. In step 3, type
C::_*
and
SHIFT-
£.
When you list the program, you will notice
that
the first
SHIFT-
£ has
changed
to
normal,
but
the
C::_*
has not.
10
PRINT"n,.
213
PRINT"'"
Now
run
the
program,
and
observe the effect
of
the reversedC::-*:The
second line has turned cyan.
To
change the program so it displays what
we
originally wanted, follow
these steps: List the program to display it
on
the screen. Position the cursor
over the
SHIFT-
£ in line
10
and
press
SHIFT-INST.
This inserts a space
and
temporarily puts the VIC in quote mode. Type CTRL-9 (RVS ON). Since it
is
in
quote mode, the VIC will insert the
RVS
ON in the
PRINT
statement (dis-
played as a reversed "R") instead
of
switching to reversed characters. When
the
PRINT
statement
is
executed, the reversed
"R"
will be recognized and the
VIC will start displaying reversed characters. Change the reversed
C::-*
to a
normal one so it won't
turn
the screen cyan again. Move the cursor over and
type a
C::
-*
over the old one.
The program should now look like this.
Ie
PRINT"~
213
PRHH"'"
Run
the
program
again,
and
you will see
that
the diamond
is
now
correctly displayed.
Adding Color to Your Display
Like reversed characters, color displays require special care. The prob-
lem here
is
slightly different: The VIC simply forgets the color
of
a character
once it is off the screen. This happens because the color
is
not actually
part
of
the character in
your
program. As mentioned earlier, there
is
an
area in
memory set aside to hold the colors
of
the characters
on
the screen. When
you list
your
program, the VIC sets the color for each character
to
the active
character color. When first powered on, VIC uses blue for the character
color.
In
Chapter
2,
you learned how to change the color from the keyboard
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