Commodore 16 - Page 38

When
you
RUN this
program. (he screen
background changes to
a
lighl
blue, and ihe
spectrum ol Commodore 1
6
colours
is shown al each
luminance
level. You'fl notice
Ihat
black is
Ihe same
al
all luminance
levels.
NOTE: Like most
ol
the
BASIC graphic lerms
reviewed in this
chapter.
COLOR may be referred
to as a
statement
or command
interchangeably.
THE GRAPHIC COMMAND
The graphics you've seen
so
tar
use
only the
keyboard
without
really
taking
advantage of your computer's capabilities.
The BASIC language
of your
Commodore 1
6
contains commands
to
draw
shapes
and
forms
through programs.
To use the graphics-related commands
of you'
computer,
you must enter
a
new
mode,
the
GRAPHIC mode. Graphic
mode can
be
considered the
drawing mode, since all
the drawing
commands are "activated".
You can't use these
commands until you
specify exactly what graphics mode
you want
to use; you specify
which type ot graphics mode
you
want
by using the GRAPHIC
command.
There
are
three different modes:
normal text,
high-
resolution graphic and
multi-colour graphic modes.
Wllh the
GRAPHIC command,
you can even have part-text, part-graphic
screens
that 'ol you can write
on
one
pari ol Ihe screen and draw
on the
rest.
The command to enter this new mode is
GRAPHIC
In
general
the GRAPHIC command looks like this
GRAPHIC mode, clear
-*
— this part is optional
Mode number Effect
1
2
Texl
High-resolution graphics
High-resolution
graphics + text
Multi-colour graphics
Multi-colour graphics
+
text
Clwr
number Effect
1
Don't
clear screen
Clear
screen
72
I
I
I
I
I
1
1 1
1 1
( (
1
I
( I
1 1
1 1
1
1
I
1
f
'
(
1 (
(
! 1
1 I
1
'
'
!
1
'
f
1
1
1 (
1
1
I
f
i 1
To switch from the normal graphics
(of text mode) to high-resolution,
just type the command
GRAPHIC 2,1 and
press
HETORH The screen
goes
blank
and Ihe cursor reappears near
the
bottom of
the
screen
Your Commodore
1 6
screen
is
divided
into 2 separale sections:
Ihe top
for graphics
and Ihe bottom
live
lines
lor
text.
It
you don't wanl the
bottom
five lines
for text,
you
can
use
the command
GRAPHIC
1,1,
but you
won't
be
able
to see
any
commands
you type.
You
can switch
back and forth from graphics
to
text
using
the
GRAPHIC command
The
command GRAPHIC switches the screen
back to text, while
GRAPHIC 2
switches
back to hign-res without erasing Ihe screen
Adding ,1 after the
command erases the screen
There
is another way to clear
the
high-resotulton
screen. The
command
SCNCLR erases the screen without changing
the
graphic
mode Once
you use
high-resolution
graphics, Ihe computer sots aside
1 0K of memory for your high-res screen. This
memory is taken
trom
the BASIC program
area. When you are through using graphics,
you
can reclaim this memory
by using
ihe
command GRAPHIC CLR.
HIGH RESOLUTION GRAPHICS
Your Commodore 1
6
screen contains
25 rows
of 40 characters
each.
or
1
000 total character positions on
the
screen.
Each
character is
formed out ol single dots, with
8
rows of
8 dots
each making an entire
character. Your screen has
a
total of 320 dots on each row, and 200
rows of
dots, or
64.000
dots
all
together. The high
resolution graphics
on
your Commodore
1
6
give
you
control over every single
dol
Using normal graphics,
you have
limited
control over me
Individual
dots Drawing
a
racing stripe or
a
playing card is
a
nice little exercise,
bul
your creation
is
limited
to using the characters (letters,
graphic
symbols,
etc.)
on your computer
keyboard. You
can slill create all
kinds of shapes and figures but
just a
fraction of what you could do if
you could control each
dot by
itself The high resolution graphics
capability
of
your
Commodore 16
lets
you do |ust that
Resolution
73