If you provide an fc parameter in a call to a Language Environment callable service, the service sets fc to a specific value called a condition token and returns it to your application. (See The effect of coding the fc parameter for more information.)

If you do not specify the fc parameter in a call to a Language Environment service, Language Environment generates a condition token for any nonzero condition and passes it to Language Environment condition handling. (See Effects of omitting the fc parameter for more information.)

The condition token is used by the routines of your application to communicate with message services, the condition manager, and other routines within the application. For example, you can use it with Language Environment message services to write a diagnostic message associated with a particular condition to a file. You can also determine if a particular condition has occurred by testing the condition token, or a symbolic representation of it. The structure of the condition token is described in Understanding the structure of the condition token, and symbolic feedback codes are discussed in Using symbolic feedback codes.

Language Environment condition tokens contain a 8-byte instance specific information (ISI) token. The ISI token can contain (depending on whether a condition occurred) insert data that further describes the condition and that can be used, for example, to write a specific message to a file. In addition to insert data, the ISI can contain qualifying data (q_data) that user-written exception handlers use to identify and react to a specific condition.