Commodore 16 - Page 41

lo lake the p'ace Ql
the angie,
even though you don't want the box
rotated This
ts
so your
computer reads the
comma as the DEFAULT
value, which means that It interprets your lack ot response
as
an
instruction
II you don't Include the comma, the 1
at
the end ol the line
Is read as the
angle
lor the box to be rotated.
Some typical forms of the BOX
command are:
Command Effect
BOX on. column 1 , row 1 , column 2, row 2
BOX
on,
col 1 .
row
1 ,
col
2,
row
2,
angle
BOX
on. col 1
,
row l
,
col
2,
row
2, .
fill
BOX off, col
t
, row
i
, col 2, row 2. angle.
Ill
Outline
Rotated
Solid
box
Erase area
of screen
Column 1 , row 1 , etc.
are
screen positions
of
endpolnts that you
specify. Column 1
,
row
1
is
the upper
left corner
of the
box while row
and
column
2 is the bottom right corner
Here
Is a
program
that
illustrates
the BOX command
(line
60)
10 COLOH 0,1
20 COLOR 1,2
30 GRAPHIC 2,1
40 A
=
RND(1)'20+ 10
50
FOR
L=0 TO 359 STEP A
60 BOX 1, 100, 30, 220, 130, L
70 NEXT L
80 FOR L« 1 TO 2000: NEXT L
90 GRAPHIC 0,1
Drawing
Circles
Your
Commodore 16 also has commands lor drawing circles Uke the
BOX command,
you
can vary the shape of the circle (to form an oval or
an ellipse), and you can rotate the oval. You can
also
just draw a
section
ol me shape
(called
an arc).
78
1
1
i
i
'
r
i
i
! 1 1
1
I
1
1
1
1 1
I
I
I
1 I
1
'
1
1
l
1
!
1 1
1
i
(
1 1
1 ! 1
(
1 1
I
I
(
I
The usual forms
of
the CIRCLE command
are:
Commam! Effect
CIRCLE on. centre column, centre row, radius
CIRCLE on, c-col, c-row, width,
height
CIRCLE on, c-col, c-row,
wid,
hi,
start, finish
CIRCLE on,
c-col,
c-row,
wtdth, height., .angle
CIRCLE
on.
c-col. c-row. wid, ht....point angle
circle
wa
arc
rotated oval
polygon
This commano draws a
circle
in
the centre of the screen:
CIRCLE
1, 160, 100,50. This
tells your computer
lo
draw
a
circle with its centre at
column 160 and row 100. with
a
radius of 50. This may
actually
produce an oval, since the dots on some TV's and monitors (
American
ones, lor
example)
are taller
than they are
wide. To change this to
a
real circle
you
must
add a
separate number to tell that the height is
different
from the width, Uke this: CIRCLE 1,160,100,50,42.
Drawing Polygons
Your Commodore 16 can also draw a square,
u-angle
or other
polygon
using the CIRCLE command. Just tell the computer
how many
degrees to go
between points on
the
circle, like Ihis. CIRCLE
1,160, 100,50,42,,,.
120. This command draws
a
triangle, since each
side
is 1 20
degrees (Remember that omitting number values while
including commas in
a
graphic command
causes
your computer to read
standard default values lor the missing number.) A simple (ormula to
get the
angle
lor a polygon with N sides is 360/N
Here's a quick program
lor drawing polygons:
10
GRAPHIC
2,1
20 INPUT-HOW MANY SIDES";A
30 IF A<2 OR A
>
100 THEN
PRINT
"DONT
BE RIDICULOUS":
GOTO 20
40 CIRCLE l.I60.80,40,33„
M
360/A
50 GOTO 20
You can
choose to
draw only an arc Instead o> a whole circle. The
CIRCLE command accepts the
starting and ending angles In degrees,
79