1.2 How HLLAPI Works

To run a HLLAPI application, you must first start the 3270 emulation program, and then run your HLLAPI application. The 3270 emulation program and the HLLAPI application must be run with the same login ID.

If the HLLAPI application manages all interaction with the host and does not require operator input to the 3270 emulation program, you can start the 3270 emulation program as a background process using the -b command-line option; for more information, refer to the SNAP-IX 3270 User's Guide or SNAP-IX TN3270 User's Guide.

HLLAPI communicates with the host computer by processing function requests made by your application program. When your application program requests a HLLAPI function, the following occurs:

1. Your application program requests the function by calling the HLLAPI library and passing it the appropriate parameters.

2. The library interprets the request.

3. The library sends the request to the 3270 emulation program.

4. The 3270 emulation program performs any necessary host communications, processes the request, and returns the result of the request.

5. The library uses returned parameters to send the results of the request to your application program.