1.8 Vendor-Extensible Fields
The methods defined in the Print System Remote Protocol specify either the DWORD or HRESULT data type for return values. DWORD return values are Win32 error codes specified in [MS-ERREF] section 2.2. Implementers reuse those values with their indicated meanings. Choosing any other value runs the risk of collisions.
HRESULT method return values are defined in [MS-ERREF] section 2.1. Vendors can define their own HRESULT values, provided they set the C bit (0x20000000) for each vendor-defined value, indicating the value is a customer code.
Print server implementations MUST generate GUIDs, as defined in [MS-DTYP] sections 2.3.4, 2.3.4.2, and 2.3.4.3, strings for the purpose of identifying specific printers. The 128-bit value encoded by the GUID string SHOULD conform to the specification in [RFC4122] section 4.