Interfaces and their interactions

EDT provides three interfaces:

• An interface at which a user program calls EDT functions
  (IEDTGLE interface)

• An interface at which routines written by a user are declared as user-defined statements. The associated routine is called in order to execute this type of user-defined statement (@USE interface).

• An interface for calling user routines (@RUN)

These three interfaces use the same control block layout.

The @USE interface also makes it possible to declare a statement filter:
the declared routine is called for each statement in order to determine whether or not the statement can be executed.

For their part, routines which implement user-defined statements as well as user routines can call EDT functions via the IEDTGLE interface (sometimes with restrictions).