DEFINE FUNCTION

        [SIC\]DEFINE FUNCTION NAME(X,Y,Z) Expression(X,Y,Z)

    Define an arithmetic user function of  several  variables.  The  maximum
    number  of  variables is 8. The function definition can reference any of
    the known mathematic operators and intrinsic or  program  defined  func-
    tions,  but  not  previously  defined user functions (i.e. user function
    definition is not recursive).