What does it do? The statement INTERFACE defines interfaces or declares them in advance. The definition of an interface consists of a declaration part that starts with INTERFACE and is ended using ENDINTERFACE. Unlike classes, an interface does not have an implemenation part. Additional variants of INTERFACE without ENDINTERFACE are used for the advance declaration of interfaces in a program.
The statements INTERFACE and associated statements ENDINTERFACE can be specified only in the global context of a program. INTERFACE and ENDINTERFACE cannot be specified within classes, procedures, and processing blocks implemented internally as a procedure (event blocks for GET and AT SELECTION-SCREEN). This applies in particular to the variant of INTERFACE specified here, which is not closed using ENDINTERFACE.
