Operation is one of open , print or explore or another operation registered with the shell for the given document-type. On modern systems it is also possible to pass a URL as File , opening the URL in Windows default browser. Win32 systems only. Fetches the value of a Win32 registry key. Key is an atom formed as a path-name describing the desired registry key.
Name is the desired attribute name of the key.
Value is unified with the value. If the value is a string it is returned as a Prolog atom. Other types are currently not supported. Get environment variable. Fails silently if the variable does not exist.