Screen
Output
The
order of
the
parameters
for
a circle
or
ellipse
is:
•
centre_across, centre_up, height, [eccentricity, angle]
The
last
two parameters
are
optional and
this
is
indicated
by
putting them inside square
brackets ( [
J
).
T2
Example
Write
a program which does
the
following:
1.
Open a window
100xl00
at
(100,50)
2.
Scale
100
in
mode 8
3.
Select black paper and clear window
4.
Make green border 2 units wide
5.
Draw
a pattern
of
SIX
coloured cl/cles.
6.
Close
the
window.
100
REMark
pattern
110
MODE
8
120
OPEN
#7,
scr
100xl00a
100x50
130
SCALE
#7,100-;-0,0
140
PAPER
#7,0
:
CLS
#7
150
BORDER
#7,2,4
160
FOR
colour
= 1
TO
6
170 INK
#7,
colour
180
LET
rot
=
2*PI!caLaur
190
CIRCLE
#7,50,50,30,O.5,rat
200
END
FOR
cataur
210
CLOSE
#7
You
can get some interesting effects
by
altering the program.
For
example try the
amendments:
160
FOR
coLour
= 1
TO
100
180
LET
rot
=
calaur*PI/50
ARCS
If
you
want
to
draw
an
arc
you
need
to
decide:
starting point
end point
amount
of
curvature.
The
first
two
items
are
straightforward but the amount
of
curvature
is
not
so
easy.
You
can do
it
by
drawing accurately or by
trial
and error but
you
must decide what angle
the arc subtends and then specify the angle
in
radians.
An
angle
of
1.5
radians would
give
a sharp bend and a
small
angle would
give
a
very
gentle curvature
Try,
for
example:
ARC
10,50
TO
50,90,1
which gives a moderate curvature
in
the
current INK
colour.
,-
- - - - - - - (50.90)
o
: angle
(10,50)
12/84
•
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