The external access interfaces (ECI, EPI, ESI)

The external interfaces allow non-CICS® applications to access and update CICS resources by calling CICS programs or by initiating CICS transactions. When used in conjunction with CICS communication, the external interfaces enable non-CICS programs to access and update resources on any CICS system. This method of using the external interfaces supports such activities as the development of graphical user interface (GUI) front ends for CICS applications and it allows the integration of CICS systems and non-CICS systems.

External Call Interface (ECI)

The ECI enables a user application to call a CICS program synchronously or asynchronously. It enables the design of new applications to be optimized for client/server operation, with the business logic on the server and the presentation logic on the client.

External Presentation Interface (EPI)

The EPI enables a user application to act as a logical 3270 terminal and to control a CICS 3270 application. It enables modern technologies, such as graphical or multimedia interfaces, to be used with traditional CICS 3270 applications.

External Security Interface (ESI)
The ESI enables user applications to verify and change passwords for specified user IDs that are managed by an external security manager (ESM) on a CICS server.

For more information on the external access interfaces, see CICS Transaction Gateway: Programming Guide and CICS Transaction Gateway: Programming Reference.