MAIN program (Top level)

End of program

Attempting to execute a subroutine nested more than 20 levels deep causes an   error.

Example: A Nested Subroutine.

The following subroutine, labeled S, calculates the value of the expression

a2 + b2 + c2 + d2

as part of a larger calculation in a larger program. The subroutine calls upon another subroutine (a nested subroutine), labeled Q, to do the repetitive squaring and addition. This saves memory by keeping the program shorter than it would be without the subroutine.