PLOT
Unlike the L 0
CAT
E command,
PLO
T may be used to determine the position of the
graphics cursor, using pixel co-ordinates.
(A
pixel is
the
smallest possible segment of
the screen).
Note
that
the
graphics cursor is not visible and is different from
the
character cursor.
There
are
640 horizontal pixels by 400 vertical pixels. The x,y co-ordinates
are
positioned with respect to
the
bottom left corner of the screen, which has x,y
co-ordinates of
0,0. Unlike the
LO
CAT
E command used for characters, the
co-ordinates
do
not
differ between modes 0,1, or
2.
To
see this, first reset
the
computer using [CONTROL]
[SHIFn
[ESC],
then
type in:
pLot
320,200
A small dot will appear
in
the
centre of
the
screen.
Now change the mode by typing in:
mode
0
pLot
320,200
You will see
the
dot is still
in
the
centre
but
is now larger. Change
the
mode again and
type
in
the
same command to see
the
effect
in
mode
2:
mode
2
pLot
320,200
The
dobs
still
in
the centre,
but
is now much smaller.
Plot several dots over
the
screen
in
various modes,
in
order to accustom yourself with
this command. When you have finished,
return
to mode 1 and clear the screen by
typing in:
mode
DRAW
First
reset
the
computer using [CONTROL]
[SHIFn
[ESC]. The D
RAW
command
draws a line from
the
current
graphics cursor position.
To
see this
in
more detail,
draw a rectangle on
the
screen by using
the
following program.
We
start
by repositioning
the
graphics cursor with a
PLO
T command,
then
DRAWing
a line from
the
graphics cursor position, up towards the top left corner,
then
from
there
to
the
right
corner etc, etc. Type in:
Chapter
1 Page
58
Foundation Course
I
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