# Using the function reference

This section provides an alphabetical reference to the system functions used by all services in Natural Access. A typical function includes:

Prototype | The prototype is followed by a list of the function 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 the Alphabetical error summary and the Numerical error summary for a list of errors returned by Natural Access 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 may be provided in the value field of the event.
Example | Example functions that start with Demo are excerpts taken from the demonstration code that is shipped with the product. Example functions that start with my are excerpts taken from sample application programs. The notation /* ... */ indicates additional code that is not shown.