Functions that the CICS Clients provide

CICS® Clients provide a set of functions for client/server computing. This section gives an overview of the most important functions; it is not meant to be exhaustive.

The External Call Interface

The External Call Interface (ECI) is an application programming interface (API) that allows a non-CICS program running on a workstation to call a CICS program located on a CICS server. This enables the program to make use of existing server routines that could be used, for example, to make enquiries on a database.

The client program can make the following types of call to a CICS server:

The External Presentation Interface

The External Presentation Interface (EPI) is an API that allows a client program to appear to a CICS server as a 3270 terminal. You could, for example, use the EPI to enable workstation users to access CICS server transactions written for 3270 terminals, without changing the server code.

The client program can start CICS transactions and send and receive standard 3270 data streams to and from the transactions. It can present the 3270 data to the user by emulating a 3270 terminal, or by means of a graphical user interface such as Windows (Windows clients).

The EPI consists of a set of calls that can be made from an application program. The calls are provided in a library that is linked to the application. Among the functions available are calls to:

The External Security interface

The External Security Interface (ESI) is an API that allows a non-CICS Client program to verify and change the passwords used by Clients to connect to a CICS server.

Terminal emulation

CICS Clients can run 3270 terminal emulators. A client terminal emulator transmits or receives standard CICS transaction routing flows to or from a CICS server. This allows a user to interact with the server, and run transactions, as if the client were a locally-attached 3270 terminal.

It is possible to run multiple terminal emulators on a single client. The emulators can be connected to the same CICS server, or to different servers.

Users can customize the colors and keyboard mapping of their emulators. Double-byte character sets (DBCS) are supported but note that CICS clients attached to CICS/400 servers do not support double-byte character sets.

Related reference
CICS Clients
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