ESL Communications Support allows the use of a Personal Computer (PC) in place of a Non-Programmable Terminal (NPT) through the use of a third-party emulator hardware and software. ESL, with the emulator, provides you with a means to customize and design a front-end for a 3270/5250 host.

With the 3270/5250 Support for ESL, a full screen of information from the host is held in a screen buffer, where its data can be accessed. The 3270/5250 Support for ESL provides facilities that allow you to examine data in the buffer, place data into specified fields, transfer data to the host, and execute other functions that can be performed by a 3270/5250 terminal. To accomplish these functions, you call the ESL Communications Server (ECS) subroutines described in this manual.

The ECS is a stimulus Dynamic Link Library (DLL) interface that provides directly callable subroutines. A single set of subroutines, including some ESL subroutines, supports both 3270 and 5250 sessions. For any given environment, a single DLL and its include file (containing function prototypes, stimulus declaration, various constant definitions, and several ESL subroutines) are provided.