DiameterAreaCircumference
Radius is distance from centre of circle to circumference of the circle
Diameter is distance from one point on circumference to another point in
circumference with the line passing through the centre of the circle
Circumference is the total length of outer border of the circle
Area is the total area of the circle
Calculate Others button computes the all other parameters of circle given
one of the four parameter
Given any one field value all others can be computed. Change any of the textbox
and press enter to compute other fields