Several ORCA functions require you to code a callback function. A callback function provides a way for the called program (the ORCA DLL or the Library Manager) to execute code in the calling program (the ORCA program executable).
How ORCA uses callbacks
ORCA uses callback functions when an unknown number of items needs to be processed. The purpose of the callback function is to process each of the returned items, and in most cases return the information to the user.
Optional or required
Some callbacks handle errors that occur when the main work is being done -- for example, when compiling objects or building executables. For handling errors, the callback function is optional. Other callbacks handle the information you wanted when you called the function -- such as each item in a directory listing. Callbacks for information functions are required.
Language requirement
ORCA functions that require the use of callback functions can be used only by programs written in languages that use pointers, such as C and C++.
When you create a new ORCA callback function, use the CALLBACK macro to specify the calling convention of the function. On the Windows platform, CALLBACK is defined as __stdcall.
