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Commodore Plus 4 - Page 207

Commodore Plus 4
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Graphics
Programming
in
BASIC
195
Multicolor
Graphic
Mode
Multicolor
graphic
mode
is
normally
used
when
the
color
restrictions
of
high
resolution
are
unacceptable.
It
is
accessed
with
GRAPHIC
Z.clearflag
The
clear
flag
is
optional
(1
clears
the
multicolor
graphic
screen,
0
or
absence
leaves
the
screen
intact).
This
statement
creates
a
multicolor
bit-mapped
screen
on
which
the
pro
grammer
can
draw
graphics
with
the
Plus/4's
graphics
statements:
BOX,
CIR
CLE,
DRAW,
and
PAINT.
A
section
of
memory
(12K
bytes)
is
set
aside
for
this
use
and
is
therefore
not
available
for
the
BASIC
program.
The
text
screen
area
of
memory
is
left
intact.
Therefore,
you
can
PRINT
on
the
text
screen
behind
the
graphics
screen,
and
the
PRINTed
data
are
revealed
when
you
return
to
text
mode.
The
Split-Screen
You
can
create
the
multicolor
bit
map
and
view
the
upper
portion of
it
and
the
lower
five
lines
of
the
text
screen
simultaneously
with
the
command:
GRAPHIC
4,ciear
flag
Again,
both
the
text
and
the
multicolor
bit
map
areas
of
memory
are
reserved.
The
use
of
this
statement
merely
reveals
the
lower
five
lines
of
the
text
screen
and
conceals
the
corresponding
portion
of
the
multicolor
bit
map.
When
the
clear
flag
is
set
to
1,
both
the
graphics
and
text
screen
are
cleared
and
the
text
cursor
is
placed
at
the
left
of
the
first
visible
text
line.
The
Coordinate
System
The
multicolor
graphic
screen
is
normally
addressed
by
a 160
by
200
coordinate
matrix.
The
horizontal
(or
x)
coordinate
ranges
from
0
at
the
left
of
the
screen
to
159
at
the
right.
The
vertical
(or
y)
coordinate
ranges
from
0
at
the
top
of
the
screen
to
199
at
the
bottom.
The x
coordinates
used
on
the
multicolor
graphic
screen
are
exactly
one-half
of
the
corresponding
x
coordinates
on
the
high-resolution
screen.
Only
the
CHAR
statement
(which
plots
characters
on
the
multicolor
graphic
screen)
uses
the
text
rows
and
columns
for
its
coordi
nates.
The
CHAR
x
and
y
are
related
to
the
multicolor
graphic
x
and
y
by
CHARy-ooordinate
-
INTimulticolor
graphicy-coordinate/8*)
and
CHAR
x-ooordinate
=
INT(inulticolor
graphic
x-coordinate/ty

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