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1 An area on a display screen inside which part of an image or file is displayed. A windows system is a means of presenting users with views of the state of a number of separate processes, each carrying out a task. The user is able to initiate, monitor, and terminate processes, each process having an associated window. The window for each process is assigned to a specific area of the display and can be moved and often resized. It may overlap or be overlapped by the windows associated with other processes (i.e. more than one window can be displayed at once). As each process runs, it updates the contents of its window, and the user can direct input to the process by placing the cursor in the window and typing or otherwise generating input. This is of value where a user with a workstation is managing a number of different related activities.

The windows system was originally conceived at Rank Xerox and was first used commercially on the Apple Macintosh computer. It is now available on most types of computer. See also windows manager, Windows, X Windows.

2 A source region in one coordinate system that is mapped into a destination region (called a viewport) by a window-to-viewport transformation. Both window and viewport are normally rectangular regions, consequently a window-to-viewport transformation consists of translation and scaling components only.

3 An allocation of messages, data units, or both, given by a receiver to a sender in a data communication protocol. It controls how much data the sender may transmit before it receives an acknowledgment from the receiver. The window is used for flow control by the receiver, to prevent the sender from transmitting more rapidly than the receiver can process. The window is also used for error management, by establishing the range of data that is unacknowledged and thus may need to be retransmitted. The selection of a proper window size is dependent upon the properties of the path between the sender and receiver: bandwidth, delay, and network congestion are important factors.

Subjects: Computing.

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