In computers, a window is one of the fundamental building blocks of a graphical user interface (GUI), along with icons, menus and the pointer. It is primarily used as a container for other interface elements, such as menus, buttons, icons, text, as well as data being worked on by the user. A window is thus the most visible part of a process running on a computer, and allows that process to display information to, and accept input from, the user.
Windows have distinct boundaries, to enable the user to distinguish interface elements belonging to different processes. They also expose standard controls to the user, for manipulating (resizing, moving, hiding and closing) the window. In most modern operating systems, windows can overlap each other, and in some cases contain child windows in what's known as a multiple document interface (MDI).
Several operating systems (or components thereof) are named after the word "window", including Microsoft Windows and the X Window System. Ironically, the latest version of Microsoft Windows, Windows 8, forgoes windows in its default Modern user interface in favor of full-screen applications.