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. Applications Some applications that provide user exits: Apache Subversion allows "hooks", which are "scripts that run when an action is performed" IBM CICS IBM CMVC user exits in the form of Kornshell scripts IBM JES 2 and 3 IBM MVS, SMS, z/OS and dozens of sub-components such as RACF, SMF, etc. IBM sort/merge package Oracle CC&B SAP R3 See also Callback Linking Hook References Control flow Subroutines