# COM user defined functions Reference

Below is a complete list of the user defined functions available in AutoIt. Click on a user defined function name for a detailed description.

When using them you need to add a #include <WinAPICom.au3>.

User Defined Function | Description
--- | ---
_WinAPI_CLSIDFromProgID | Looks up a CLSID in the registry, given a ProgID
_WinAPI_CoInitialize | Initializes the COM library for use by the calling process
_WinAPI_CoTaskMemAlloc | Allocates a block of task memory
_WinAPI_CoTaskMemFree | Frees a block of task memory
_WinAPI_CoTaskMemRealloc | Changes the size of a previously allocated block of task memory
_WinAPI_CoUninitialize | Closes the COM library on the current process
_WinAPI_CreateGUID | Creates a globally unique identifier (GUID)
_WinAPI_CreateStreamOnHGlobal | Creates a stream object that uses a memory handle to store the stream contents
_WinAPI_GetHGlobalFromStream | Retrieves the global memory handle to a stream
_WinAPI_ProgIDFromCLSID | Retrieves the ProgID for a given CLSID
_WinAPI_ReleaseStream | Releases a stream object