Windows 1.0

Microsoft began developing a graphical user interface (GUI) in 1981. The development of Windows began after Microsoft founder Bill Gates saw a demonstration at

COMDEX 1982 of VisiCorp's Visi On, a GUI software suite for IBM PC compatible computers. In 1983 Microsoft learned that Apple's own GUI software—also bit-mapped, and based in part on research from Xerox PARC—was much more advanced; Microsoft decided they needed to differentiate their own offering. In August 1983, Gates recruited Scott McGregor, one of the key developers behind PARC's original windowing system, to be the developer team lead for Windows 1.0 Microsoft first presented Windows to the public on November 10, 1983. Requiring two floppy disk drives and 192 KB of RAM, Microsoft described the software as a device driver for MS-DOS 2.0. By supporting cooperative multitasking in tiled windows when using well-behaved applications that only used DOS system calls, and permitting non-well-behaved applications to run in a full screen, Windows differed from both Visi On and Apple Computer's Lisa by immediately offering many applications. Unlike Visi On, Windows developers did not need to use Unix to develop IBM PC applications; Microsoft planned to encourage other companies, including competitors, to develop programs for Windows by not requiring a Microsoft user interface in their applications.

Many manufacturers of MS-DOS computers such as Compaq, Zenith, and DEC promised to provide support, as did software companies such as Ashton-Tate and Lotus. After previewing Windows, BYTE magazine stated in December 1983 that it "seems to offer remarkable openness, reconfigurability, and transportability as well as modest hardware requirements and pricing … Barring a surprise product introduction from another company, Microsoft Windows will be the first large-scale test of the desktop metaphor in the hands of its intended users".

From early in Windows' history Gates viewed it as Microsoft's future. He told InfoWorld magazine in April 1984 that "Our strategies and energies as a company are totally committed to Windows, in the same way that we're committed to operating-system kernels like MS-DOS and Xenix. We're also saying that only applications that take advantage of Windows will be competitive in the long run." IBM was notably absent from Microsoft's announcement, and by late 1984, the press reported a "War of the Windows" between Windows, IBM TopView, and Digital Research's Graphics Environment Manager (GEM).

Microsoft had promised in November 1983 to ship Windows by April 1984, but subsequently denied that it had announced a release date, and predicted that Windows would ship by June 1985. During its development and before its windowing system was developed, it was briefly referred to by the codename "Interface Manager". De-emphasizing multitasking, the company stated that Windows' purpose, unlike that of TopView, was to "turn the computer into a graphics-rich environment" while using less memory. After Microsoft persuaded IBM that the latter needed a GUI, in April 1987 the two companies announced the introduction of OS/2 and its graphical OS/2 Presentation Manager, which were supposed to ultimately replace both MS-DOS and Windows.

Release versions: Windows 1.01–1.04
Windows version 1.01, released on November 20, 1985, was the first public release of Windows. The first international release, Windows version 1.02, was released in May 1986. Windows version 1.03, released in August 1986, included enhancements that made it consistent with the international release like drivers for European keyboards and additional screen and printer drivers. Windows version 1.04, released in April 1987, added support for the new IBM PS/2 computers, although no support for PS/2 mice or new VGA graphics modes was provided. However, on May 27, 1987, an OEM version was released by IBM, which added VGA support, PS/2 mouse support, MCGA support, and support for the 8514/A display driver. IBM released this version on three 3.5 inch 720k floppies, and offered it as part of their "Personal Publishing System" and "Collegiate Kit" bundles.

Features
Windows 1.0 offers limited multitasking of existing MS-DOS programs and concentrates on creating an interaction paradigm (cf. message loop), an execution model and a stable API for native programs for the future. Due to Microsoft's extensive support for backward compatibility, it is not only possible to execute Windows 1.0 binary programs on current versions (albeit only 32-bit) of Windows to a large extent, but also to recompile their source code into an equally functional "modern" application with just limited modifications. Windows 1.0 is often regarded as a "front-end to the MS-DOS operating system", a description which has also been applied to subsequent versions of Windows. Windows 1.0 is an MS-DOS program. Windows 1.0 programs can call MS-DOS functions, and GUI programs are run from .exe files just like MS-DOS programs. However, Windows .exe files had their own "new executable" (NE) file format, which only Windows could process and which, for example, allowed demand-loading of code and data. Applications were supposed to handle memory only through Windows' own memory management system, which implemented a software-based virtual memory scheme allowing for applications larger than available RAM. Because graphics support in MS-DOS is extremely limited, MS-DOS applications have to go to the bare hardware (or sometimes just to the BIOS) to get work done. Therefore, Windows 1.0 included original device drivers for video cards, a mouse, keyboards, printers and serial communications, and applications were supposed to only invoke APIs built upon these drivers. However, this extended to other APIs such as file system management functions. In this sense, Windows 1.0 was designed to be extended into a full-fledged operating system, rather than being just a graphics environment used by applications. Indeed, Windows 1.0 is a "DOS front-end" and cannot operate without a DOS environment (it uses, for example, the file-handling functions provided by DOS). The level of replacement increases in subsequent versions. The system requirements for Windows 1.01 constituted CGA/HGC/EGA (listed as "Monochrome or color monitor"), MS-DOS 2.0, 256 KB of memory or greater, and two double-sided disk drives or a hard drive. Beginning with version 1.03, support for Tandy and AT&T graphics modes was added. MS-DOS Executive file manager. Windows 1.0 runs a shell program known as the MS-DOS Executive, which is little more than a mouse-able output of the DIR command that does not support icons and is not Y2K-compliant. Other supplied programs are Calculator, Calendar, Clipboard Viewer, Clock, Notepad, Paint, Reversi, Cardfile, Terminal and Write. Windows 1.0 does not allow overlapping windows. Instead all windows are tiled. Only dialog boxes can appear over other windows, but cannot be minimized.