What is the fine-grained topic of the following text: An AS/400 exit program (so called because the system exits to the program in the middle of a request from the user) is not used - as might be expected - to exit from a program, but to process user requests: it monitors user activity, checks to see if user requests comply with installation rules, and rejects those requests that contravene those rules. Only return the topic.
AS/400 Exit Program Functionality