Radio Shack TRS-80 User Manual page 107

Chapter 20
And
It
Draws
Pictures
Too!
Your
TRS-80
can
draw
an
endless variety
of pictures
on
the
Video Display
screen.
You
will
learn
some
of the
basic
procedures
and
capabilities in this
Chapter. Later
on
there's
even
more
pictures!
After
that,
what you
create
is
limited only
by your
own
imagination.
Who
knows
. . .
you
may
write
a
graphics
program
artistically
equivalent to the
Mona
Lisa.
Now,
on
to 2
of the 4 graphic commands:
SET
turns
on
(or
lights
up
if
you
will) a particular section,
block or "light" on the screen,
RESET
turns off (or blackens) a
particular "light".
For graphics, the screen
is
divided into a large
number
•
of sections.
See the Video
Display
Worksheet on
the next page.
Each
"light"
is
a
rectangular
block 2 dots wide
by
8
dots high;
and
each
has
its
own
"address".
For example
:
SET (55,32)
means
—
"turn on
the light"
at
the junction of
55th
"X"
Street
and 32nd
"Y"
Avenue.
X
is
the horizontal address counting
across
from the left-hand
side
of the
screen.
Y
is
the
vertical
address,
counting
down from
the top
of the
screen.
So everything
starts
from
the
upper left-hand corner.
Type
in
50
SET
(
55
,
32
)
Clear the screen
and
RUN
.
There
it
is!
The
light
came
on.
Check
the
Video
Display
Worksheet
carefully
to find the
address
of
that
light.
Did
it
show up
in
about the right place??
ARTIST
105