This section is intended to show you how to manipulate devices from a DP4 applications, written in QA Build or C. In either case functionality is available for the following:
Device Group initialisation
POD initialisation
POD output
POD status retrieval
Selecting one or more input devices from which input is allowed
Reading input data
Identifying which device returned the data, if more than one input device is enabled
The DP4 terminal manager will continue to run applications that require an OSDI even when the OSDI is not or cannot be loaded. Obviously, how well the application runs will depend on what the OSDI was needed for. Typically applications can run without the OSDI as long as they do not need particular data to be returned by calls to status functions. Application programmers normally try to arrange for their programs to run without the OSDI present as this is often very convenient for testing.
If the OSDI does not exist or cannot be loaded for whatever reason, DP4 system warning 118 will be displayed and the program will run without the OSDI.