Sinclair QL Beginner's Manual page 85

If you add two more parameters:
e.g. CIRCLE 50,50,40,.5
You will get an ellipse. The keywords CIRCLE and ELLIPSE are interchangeable.
The height of the ellipse is 40 as before but the horizontal 'radius' is now only 0.5 of the height. The
number 0.5 is called the eccentricity. If the eccentricity is 1 you get a circle if it is less than 1 and
greater than zero you get an ellipse. If you want to tilt an ellipse you can change the fifth parameter,
for example:
CIRCLE 50,50,40,.5,1
This will tilt the ellipse anti-clockwise by one radian, about 57 degrees, as shown in figure
below