CIRCLE Statement Details
Syntax
CIRCLE [STEP] (x,y),radius[,[color][,[start][,[end][,aspect]]]]
Argument Description
STEP The STEP option specifies that x and y are offsets
relative to the current graphics cursor position.
x,y The x and y coordinates for the center of the circle
or ellipse.
radius The radius of the circle or ellipse in the current
coordinate system.
color The attribute of the desired color. The default color is
the foreground color. See the and
the for more information on
how to specify a color in different display screen modes.
start, end The start and end angles, in radians, for the arc to
draw. The start and end arguments are used to draw
partial circles or ellipses. The arguments may range
in value from -2PI radians to 2PI radians, where
PI= 3.141593. The default value for start is 0 radians.
The default value for end is 2PI radians.
If start or end is negative, then CIRCLE draws a
radius to that point on the arc and treats the angle
as if it were positive.
The start angle can be less than the end angle. If
you specify end but not start, the arc is drawn from
2PI to end; if you specify start, but not end, the
statement draws an arc from start to zero.
aspect The aspect ratio, or the ratio of the y radius to the
x radius. The default value for aspect is the value
required to draw a round circle in the screen mode.
This value is calculated as follows:
4 * (ypixels/xpixels)/3
where xpixels by ypixels is the screen resolution.
For example, in screen mode 1, where the resolution
is 320 x 200, the default for aspect would be:
4 * (200/320)/3, or 5/6.
If the aspect ratio is less than one, radius is the
x radius. If aspect is greater than one, radius is
equal to the y radius.
To draw a radius to angle 0 (a horizontal line segment to the right),
do not give the angle as -0; use a very small nonzero value instead
as shown:
' Draws a pie-shaped one-quarter wedge of a circle:
SCREEN 2
CIRCLE (200,100),60,,-.0001,-1.57
You may omit an argument in the middle of the statement, but you must
include the argument's commas. In the following statement, the color
argument has been omitted:
CIRCLE STEP (150,200),94,,0.0,6.28
If you omit the last argument, you do not include the commas.
The last point that CIRCLE references, after drawing, is the
center of the ellipse or circle. You may use coordinates that are
outside the screen or viewport.
You may show coordinates as absolutes, or you may use the STEP
option to show the position of the center point in relation to the
previous point of reference. For example, if the previous point of
reference is (10,10), then the following statement causes a circle
to be drawn with radius 75 and center offset 10 from the current x
coordinate and 5 from the current y coordinate. The circle's
center is (20,15).
CIRCLE STEP (10,5), 75