What is EHLLAPI?

The Emulator High-Level Language Application Programming Interface (EHLLAPI) is an interface provided by a terminal emulator that allows a program to behave like an operator sitting at a terminal. The program, which types keystrokes and reads text from a host screen, is called a programmed operator. The programmed operator can automate repetitive tasks and provide better interfaces to existing or legacy applications.

EHLLAPI was designed to use the same communication protocol as existing emulator programs; this means that all existing wiring and control units can continue to be used. Existing host applications do not need to be aware that they are now interacting with programs rather than real users. However, because the communication protocol was designed to handle human response-times and speeds, EHLLAPI is best for low-volume transactions. Massive transfers of data can be accomplished more quickly using more direct techniques such as APPC or CICS.