# Using the function reference

A prototype of each function is shown with the function description and details of all arguments and return values. A typical function description includes:

Prototype | The prototype is shown followed by a listing of the function's arguments. NMS data types include: WORD 16-bit unsigned DWORD 32-bit unsigned INT16 16-bit signed INT32 32-bit signed BYTE 8-bit unsigned If a function argument is a data structure, the complete data structure is defined.
Return values | The return value for a function is either SUCCESS or an error code. For asynchronous functions, a return value of SUCCESS indicates the function was initiated; subsequent events indicate the status of the operation. Refer to NMS ISDN errors for a listing of all errors returned by NMS ISDN functions.
Events | If events are listed, the function is asynchronous and is complete when the DONE event is returned. If there are no events listed, the function is synchronous. Additional information such as reason codes and return values can be provided in the value field of the event. Refer to NMS ISDN events and NMS ISDN reasons for information on all NMS ISDN events and reason codes.
Details | Information specific to the operation and use of a function.
See also | Functions related to the function being described.
Example | An example code fragment. The notation /* ... */ indicates additional code that is not shown.