•
From
Basic
to
SuperBASIC
In
a later chapter
we
will
explain how other graphics facilities, such
as
drawing circles,
THE
BASIC
SCREEN
can be handled but here
we
outline
the
pixel-oriented
features,
There
are
two modes
which may be activated
by
any
of
the
follOWing:
Low resolution
8 Colour Mode
256 pixels across, 256 down
High resolution
4 Colour Mode
512 pixels across, 256 down
MODE
256
MODE 8
MODE
512
MODE 4
•
In
both modes pixels
are
addressed
by
the range
of
numbers:
o-
511
across
and
0 - 255 down
Since mode 8 has only half the number
of
pixels across the screen
as
mode
4,
mode
8 pixels
are
twice
as
wide
as
mode 4
pixels
and sc
in
mode 8 each
pixel
can
be
specified
by two coordinates.
For
example:
o or 1 2 or 3
510
or
511
It
also
means that you use
the
same range
of
numbers for
addreSSing
pixels Irrespective
of
the mode, Always think 0-511 across and
0-255
down,
If
you
are
using a television then not
all
the pixels may be
visible.
The colours available
are:
COLOURS
MODE
256
Code
MODE
512
black
0
black
blue
1
red
2
red
magenta
3
green 4
green
cyan
5
yellow
6
white
•
white
7
You
may find the following mnemonic helpful
in
remembering the codes:
Bonny Babies Really Make Good Children,
You
Wonder
In
the hlgh-resolulion mode each colour can be selected by one
of
two
codes,
You
will
see
later how a startling range
of
colour and stipple (texture) effects can be produced
if
you have a goad quality colour
mOnitor.
Some
of
the screen presentation keywords are as
fallows:
INK colour foreground colour
BORDER
width, colour
12184
draw border
at
edge
of
screen
or window
PAPER
colour background colour
BLOCK
Width,
height, across, down, colour colour a rectangle which has
its
top left hand corner
at
position
across, down
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