Summary of Subroutines and Functions

SUBROUTINES	FUNCTIONS
Invoked by using the CALL instruction followed by the subroutine name and optionally up to 20 arguments.	Invoked by specifying the function's name immediately followed by parentheses that optionally contain up to 20 arguments.
Can be internal or external Internal Can pass information by using common variables Can protect variables with the PROCEDURE instruction Can pass information by using arguments External Must pass information by using arguments Can use the ARG instruction or the ARG built-in function to receive arguments	Can be internal or external Internal Can pass information by using common variables Can protect variables with the PROCEDURE instruction Can pass information by using arguments External Must pass information by using arguments Can use the ARG instruction or the ARG built-in function to receive arguments
Uses the RETURN instruction to return to the caller.	Uses the RETURN instruction to return to the caller.
Might return a value to the caller.	Must return a value to the caller.
Returns a value by placing it into the REXX special variable RESULT.	Returns a value by replacing the function call with the value.