A function returning 3.14159265.
You can use PI to calculate the circumference and area of a circle. The example below calculates the circumference and area of a circle of a given radius.
10 CLS 20 INPUT "What is the radius of the circle ",rad 30 PRINT "The circumference is: ";2*PI*rad 40 PRINT "The area is: ";PI*rad*rad 50 END
PI can also be used to convert degrees to radians and radians to degrees.