CALL
From MidrangeWiki
CALL is an operation used in different kinds of OS/400 Programming languages to call a sub-program.
Normally when the sub-program has completed, control is returned to wherever it was called from. The process of calling can send some parameters to the called program, which can also return information to the parent.
We have to be careful ... what is passed is a string of characters so the layout of the data being sent needs to match what is to be received.