exit points? (was: does PAM for AS400 exist?)

pam:
> I exist!
:)

> By the way, I find reading threads like this really unnerving.
?What part?

So Pluggable Authentication Modules don't exist (as so named) on AS400.

But there do seem to be hooks into the security layer (and other OS
functions, for that matter) through something called "exit points".  To my
ear, these sound like "callbacks with formally-defined interfaces" that
have some standard implementation that can be overridden by creating the
right program with the right name and procedures, and installing it with
appropriate privs in a particular location.  How accurate is that reading?

What, at any level of technical detail, is an exit point?

-Jared