Returns the numeric constant pi.
The numeric constant pi (3.141592) is the ratio of the circumference of a circle to its diameter.
The number of decimal places displayed in the value returned by PI(В ) is determined by SET DECIMALS.
CLEAR ? PI( ) && Displays 3.14 STORE 2.30 TO gnRadius STORE PI( ) * gnRadius^2 TO gnArea ? gnArea && Displays 16.6190