CTR+DIA allows you to create a circle by specifying a
center position and a diameter.

Enter a value for the diameter and press <Enter>, or
accept the default value displayed in parentheses by
pressing <Enter>.

Indicate the center point of the circle, using a Position
Menu option.

In 2-D construction mode, the center point is projected to
the current construction plane, and the circle is created 
in the current construction plane.

In 3-D construction mode, the circle is created in the 
plane that is parallel to the current construction plane 
and passes through the center point.
