Radio Shack TRS-80

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