HLLAPI is a standard programming interface that allows programmatic access to a TN3270 and TN5250 host emulator sessions. Functions are provided for reading host screen data (such as the characters and attributes), for sending keystrokes, and for performing other emulator-related functions.

The EHLLAPI interface is a single call-point interface. There is a single callable API through which all EHLLAPI functions are requested. On each call to the interface the application provides a function number which identifies the function requested, a pointer to a data buffer, a pointer to the length of the data buffer, and a pointer to a return code.

WinHLLAPI is based on the familiar EHLLAPI.API. It encompasses all of its existing functionality and adds extensions that take advantage of the Windows message-driven environment.

To learn more about HLLAPI, take a look at the HLLAPI Reference.