A specification for device-independent windowing operations on bit map display devices. It was developed initially at MIT as part of the DEC/IBM/MIT Project Athena and is now a de facto standard supported by the X Consortium. X uses a client/server protocol, the X protocol. The server is the computer or X terminal with the screen, keyboard, mouse and server program and the clients are application programs. Clients may run on the same computer as the server or on a different computer, communicating over Ethernet via TCP/IP protocols.