A window is an opening in a wall , door , roof or vehicle that allows the passage of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent material, a sash set in a frame  in the opening; the sash and frame are also referred to as a window. Windows often have a latch or similar mechanism to lock the window shut or to hold it open by various amounts. The Romans were the first known to use glass for windows, a technology likely first produced in Roman Egypt , in Alexandria ca. Paper windows were economical and widely used in ancient China , Korea and Japan. In England , glass became common in the windows of ordinary homes only in the early 17th century whereas windows made up of panes of flattened animal horn were used as early as the 14th century.
Microsoft Windows , commonly referred to as Windows , is a group of several proprietary graphical operating system families, all of which are developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. Microsoft introduced an operating environment named Windows on November 20, , as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces GUIs. Apple came to see Windows as an unfair encroachment on their innovation in GUI development as implemented on products such as the Lisa and Macintosh eventually settled in court in Microsoft's favor in On PCs, Windows is still the most popular operating system. However, in , Microsoft admitted losing the majority of the overall operating system market to Android ,  because of the massive growth in sales of Android smartphones. This comparison, however, may not be fully relevant, as the two operating systems traditionally target different platforms. Still, numbers for server use of Windows that are comparable to competitors show one third market share, similar to that for end user use. The most recent version for server computers is Windows Server , version
In computing, a window is a graphical control element. It consists of a visual area containing some of the graphical user interface of the program it belongs to and is framed by a window decoration. It usually has a rectangular shape  that can overlap with the area of other windows. It displays the output of and may allow input to one or more processes. Windows are primarily associated with graphical displays, where they can be manipulated with a pointer by employing some kind of pointing device. Text-only displays can also support windowing, as a way to maintain multiple independent display areas, such as multiple buffers in Emacs. Text windows are usually controlled by keyboard, though some also respond to the mouse. A graphical user interface GUI using windows as one of its main " metaphors " is called a windowing system , whose main components are the display server and the window manager. They used overlapping windows. Apple had worked with PARC briefly at that time.
An operating system OS is system software that manages computer hardware , software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time , mass storage , printing, and other resources. For hardware functions such as input and output and memory allocation , the operating system acts as an intermediary between programs and the computer hardware,   although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. The dominant desktop operating system is Microsoft Windows with a market share of around Other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications.