Goto - Radio Shack TRS-80 User Manual

Let
There Be
Light
Let's light
up a spot on the screen, then interrogate that
point and
see
what
happens. Type:
10
Y=1:N=0
20 IN.
"DO
YQU
WISH
TO
LIGHT THE BLOCK
(Y/N)"jQ
30
CLS
40 IF
Q
= GOTO 80
50 SET(75,20)
60
GOTO
100
80
RESET(75,20)
100
IF
POINT(75,20)
=
1
P.AT200,X(Y,
" IS LIT"
200
IF
POINT(75,20> =
P
.
AT200
,
X
;
Y
,
"
I
S
DARK
"
999
G.
999
And
RUN
several times.
Answer
either
YES
or
NO,
following the
program
action to see
what
is
happening. Pretty simple
isn't it?
Really sort
of
a
status-reporting system.
Think
what
we
could
do
if
we
set
something
like this
up
in
2 nested
FOR-NEXT
loops so
we
scanned
the entire screen
and got a
status
report
on each
point.
Hmmm.
Almost
like
a radar
scan of the terrain.
Hmmm
some more.
2001 Here
We Come
Snug up your
seat belt,
type and
RUN
the following program, then
sit
back and watch
POINT
in
action.
Study
the display very carefully as
it
runs,
looking for the
many
things
that occur. This
3%
minute "moving
picture" really
tells all
you need
to
know
about the
POINT
statement.
10
REM
*
DEMONSTRATION
OF
GRAPHICS 'POINT
1
STATEMENT *
20 P=15
:
L=l 19
30
CLS
40
P.AT5 ."THIS
IS A
DEMONSTRATION
OF
THE POINT STATEMENT
";
138
Y
and
N
stand
Cor
Yes and No.
Your
input
can be
.
.
.«itteeir¥orY^,,N,.ar
:
No
i
: "<^.^rj;^>:^^i>^:^£is^s$