Without
the semicolons. the
PET
performs a carriage return after each statement
and the top line
will
look like this:
r
-,
The other three sides
are
drawn in a sequence similar to lines 10 and
15.
Line 20 begins the next sequence. then converts the linear segment to
FOR
...
NEXT/PRINT statements. calling the time delay subroutine in that
PRINT
loop. Don't forget to include the cursor controls to compensate for the automatic
right cursor movement inside the
FOR
...
NEXT
loops for the vertical sides of the
square:
F'RHlT"
'00"
right
si
de
PRINT<RIGHT
L1NE VERT.
><CURSOR
L.
>
<CURSOR
DOWN>
F'RINT"-I
••
"
botlom
PRINT<BOTTOM
L1NE
HORIZ.><CURSOR
L.>
<CURSOR
L.
>
F'F<:INT"lln"
leftside
PRINT<LEFT
L1NE VERT.
><CURSOR
L. >
<CURSOR
UP>
The program listing looks like this:
5
F'R
1
NT":']"
.;
1
(1
F'R
1
NT"
r".;
:
GOSLIE:
1
(1JC:1
15
FOR
l=lTO
5:F'RINT"-".;
: GOSUB
l(t(t:NEXT
1
2(1
F'R
1
tH"
1".;
: GOSUB 1
JC:1(t
25
FOR 1= 1
TO
5:
F'R
1
t·lT"
'[!!l".; : GOSUB 1€l(t :
NE>~T
1
30
F'RItH
"...J"
.;
:GOSUB
1130
35
FOF.:
1= 1TO
5:
F'R
1
NT"
-1.1";
:GOSUB 1
(10
:
NEXT
1
413
F'R
1
NT"
L".; :
GOSLŒ
1
(113
45
FOR
l=lTO
S:F'RIHT"lln".;
: GOSUB
l(t0:NE>::T
1
5(1
ENII
11313
FOR
S=
1
TO
113:
l'~E;:'::T
~T:
RETURN
Now. try a trial
run.
Does your square look like this?
1
Il
F.:EAII'y'. 1
1 1
1 1
1 1
LI
__
If this design appeared instead of a perfect square. some of the
cu
rsor controls
were left out. The
PET
did exactly
what
it
was programmed to
do.
so
where
is
the
problem?
Take
a closer look at the program.
We
included cursor controls
within
the
FOR
...
NEXT
loops for ail four sides of the square. Now look at the screen. The
problem
is
not
with
the sides. The problem. therefore. must
be
in
the corners.
Look at statements 20. 30. and 40. We forgot the cursor controis after each corner
234
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