Windows 1.0

Windows 1.0 is a 16-bit graphical operating environment released on November 20, 1985. It was Microsoft's first attempt to implement a multi-tasking graphical user interface-based operating environment on the PC platform.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 of Windows to a large extent, but also to recompile their source code into an equally functional "modern" application with just limited modifications.[citation needed].
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.

Windows 3.0

Windows 3.0 is the third major release of Microsoft Windows, and came out on May 22, 1990. It became the first widely successful version of Windows (see history of Microsoft Windows) and a powerful rival to Apple Macintosh and the Commodore Amiga on the GUI front. It was succeeded by Windows 3.1.Windows 3.0 succeeded Windows 2.1x and included a significantly revamped user interface as well as technical improvements to make better use of the memory management capabilities of Intel's 80286 and 80386 processors. Text-mode programs written for MS-DOS could be run within a window (a feature previously available in a more limited form with Windows/386 2.1), making the system usable as a crude multitasking base for legacy programs. However, this was of limited use for the home market, where most games and entertainment programs continued to require raw DOS access.
The MS-DOS Executive file manager/program launcher was replaced with an icon-based Program Manager and a list-based File Manager, thereby simplifying the launching of applications. The MS-DOS Executive is also included as an alternative to these. The Control Panel, previously available as a standard-looking applet, was re-modeled after the one in Mac OS. It centralized system settings, including limited control over the color scheme of the interface. A number of simple applications were included, such as the text editor Notepad and the word processor Write (both inherited from earlier versions of Windows), a macro recorder (new; later dropped), and a calculator (also inherited). The earlier Reversi game was complemented with a card game named Solitaire.
Windows 3.0 was the last version of Windows to advertise 100% compatibility with older Windows applications

Windows 3.1x

Windows 3.1x is a graphical user interface and a part of the Microsoft Windows software family. Several editions were released between 1992 and 1994, succeeding Windows 3.0. This family of Windows can run in either Standard or 386 Enhanced memory modes. The exception is Windows for Workgroups 3.11, which can only officially run in 386 Enhanced mode.

Windows NT 3.51

Windows NT 3.51 is the third release of Microsoft's Windows NT line of operating systems. It was released on May 30, 1995, nine months after Windows NT 3.5. The release provided two notable feature improvements; firstly NT 3.51 was the first of a short-lived outing of Microsoft Windows on the PowerPC CPU architecture. The second most significant enhancement offered through the release was that it provides client/server support for interoperating with Windows 95, which was released three months after NT 3.51. Windows NT 4.0 became its successor a year later; Microsoft continued to support 3.51 until December 31, 2001.

Windows 95

Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products. During development it was referred to as Windows 4.0 or by the internal codename Chicago.
Windows 95 was intended to integrate Microsoft's formerly separate MS-DOS and Windows products and includes an enhanced version of DOS, often referred to as MS-DOS 7.0. It features significant improvements over its predecessor, Windows 3.1, most visibly the graphical user interface (GUI) whose basic format and structure is still used in later versions such as Windows Vista. There were also large changes made to the underlying workings, including support for 255-character mixed-case long filenames and preemptively multitasked protected-mode 32-bit applications. Whereas its predecessors are optional "operating environments" requiring the MS-DOS operating system (usually available separately), Windows 95 is a consolidated operating system, which was a significant marketing change.

MS DOS

MS-DOS (short for Microsoft Disk Operating System) is an operating system commercialised by Microsoft. It was the most commonly used member of the DOS family of operating systems and was the dominant operating system for the PC compatible platform during the 1980s. It has gradually been replaced on consumer desktop computers by various generations of the Windows operating system.MS-DOS was originally released in 1981 and had eight major versions released before Microsoft stopped development in 2000. It was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It also provided the platform on which early versions of Windows ran.

Windows 2.0

Windows 2.0 allowed application windows to overlap each other, unlike its predecessor Windows 1.0, which could only display tiled windows. Windows 2.0 also introduced more sophisticated keyboard-shortcuts and the terminology of "Minimize" and "Maximize", as opposed to "Iconize" and "Zoom" in Windows 1.0.The first Windows versions of Microsoft Word and Microsoft Excel ran on Windows 2.0. Third-party developer support for Windows increased substantially with this version (some shipped the Windows Runtime software with their applications, for customers who had not purchased the full version of Windows). However, most developers still maintained DOS versions of their applications, as Windows users were still a distinct minority of their market.