User exit

In some cases security controls restrict exits to authorized users, e.g., EXCP appendages in MVS.

The earliest use of this term involved operating systems to let customized code temporarily take control when a pre-designated event occurred.

Procedures provided as user exits are typically compiled into a static library and linked directly with the package to produce an executable program.

Other vendors such as SAP, Oracle, IFS, HP, Macro4, Compuware, CA all employ user exits in some of their software products.

If files containing user-created content are meant to follow a standard, the (file) Open command of a word-processing document can invoke a user exit that does validation and, if necessary, returns an error code.