It all started in April 4, 1975, when Paul Allen and Bill Gates founded Microsoft who is actually a combination of “microcomputer software”.

When the market received the IBM PC bang in the mid-1980, Microsoft, thanks to IBM came up with MS-DOS. The runner up was Digital Research. So, in August 12, 1981 Microsoft starts working at MS-DOS. They started from a clone of QDOS for which they paid $50000, clone renamed as PC-DOS.

But MS-DOS got alive only thanks to COMPAQ who managed to clone the IBM BIOS and so the world got a new player on the computer manufacturers. Thanks to this, Microsoft began licensing its operating system for use on non-IBM PC clones and so MS-DOS (Microsoft Disk Operating System) entered the scene.

In 1985, Microsoft moves to Ireland and there they founded the first international production facility. And there, on November 20 Microsoft released its first retail version of Microsoft Windows, originally a graphical extension for its MS-DOS operating system. In August, Microsoft and IBM partnered in the development of a different operating system called OS/2. OS/2 was marketed in connection with a new hardware design proprietary to IBM, the PS/2.Shortly afterwards on February 16, 1986, Microsoft relocated to Redmond, Washington. Around one month later, on March 13, the company went public with an IPO, raising US$61 million at US$21.00 per share. By the end of the trading day, the price had risen to US$28.00. In 1987, Microsoft eventually released their first version of OS/2 to OEMs.

The early versions of Windows were often thought of as just graphical user interfaces or desktops, mostly because they were started from MS-DOS and used it for file system services. However even the earliest 16-bit Windows versions already assumed many typical operating system functions, notably having their own executable file format and providing their own device drivers (timer, graphics, printer, mouse, keyboard and sound) for applications. Unlike DOS, Windows allowed users to execute multiple graphical applications at the same time, through co-operative multitasking, something which competitors (like GEM) did not offer. Finally, Windows implemented an elaborate, segment-based, software virtual memory scheme which allowed it to run applications larger than available memory: code segments and resources were swapped in and thrown away when memory became scarce, and data segments moved in memory when a given application had relinquished processor control, typically waiting for user input. Examples include Windows 1.0 (1985) and Windows 2.0 (1987) and its close relative Windows/286.

In 1985, Microsoft launches Windows 1.0 which offered limited multitasking of existing MS-DOS programs and concentrated on creating an interaction paradigm, an execution model and a stable API for native programs for the future. This first version of Windows ran a shell program known as MS-DOS Executive. Other supplied programs were Calculator, Calendar, Cardfile, Clipboard viewer, Clock, Control Panel, Notepad, Paint, Reversi, Terminal, Write, and the command prompt.

Released on November 1, 1987, Windows 2.0 allowed for windows to overlap each other, in contrast to Windows 1.0, which could only display tiled windows (this limitation was artificially imposed due to lawsuits from Apple Computer; dialogs and drop-down menus were in fact overlapping windows in Windows 1.0). This version also introduced the window-manipulation terminology of “Minimize” and “Maximize”, as opposed to “Iconize” and “Zoom” in Windows 1.0, and a more sophisticated keyboard-shortcut mechanism in which shortcut keys were identified by underlining the character that, in conjunction with the “Alt” key, would cause them to be selected. File management tasks were still managed by use of the MS-DOS Executive program, which was more list-driven than icon-oriented.

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 shipping 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.

Windows 3.0(1990) and Windows 3.1 (1992) came with virtual memory and loadable virtual device drivers (VxDs). But only with the 32-bit File Access in Windows for Workgroups 3.11, Windows could finally stop relying on DOS for file management. Leveraging this, Windows 95 introduced Long File Names, reducing the 8.3 DOS to the role of a boot loader.

There were three releases of Windows 95 (the first in 1995, then subsequent bug-fix versions in 1996 and 1997, only released to OEMs, which added extra features such as FAT32 support). Microsoft’s next OS was Windows 98; there were two versions of this (the first in 1998 and the second, named “Windows 98 Second Edition”, in 1999). In 2000, Microsoft released Windows Me (Me standing for Millennium Edition), which used the same core as Windows 98 but adopted the visual appearance of Windows 2000, as well as a new feature called System Restore, allowing the user to set the computer’s settings back to an earlier date. It was not a very well received implementation, and many user problems occurred. ME was considered a stopgap to the day both product lines would be seamlessly merged. Microsoft left little time for Windows Me to become popular before announcing their next version of Windows which would be called XP.

Originally designed and marketed for higher-reliability business use with no DOS heritage. The first release was Windows NT 3.1 (1993, numbered “3.1″ to match the Windows version and to one-up OS/2 2.1, IBM’s flagship OS co-developed by Microsoft and Windows NT’s main competitor at the time), which was followed by NT 3.5 (1994), NT 3.51 (1995), and NT 4.0 (1996); the latter implemented the Windows 95 user interface. Microsoft then moved to combine their consumer and business operating systems.

Their first attempt, Windows 2000, failed to meet their goals, and was released as a business system. The home consumer edition of Windows 2000, codenamed “Windows Neptune”, ceased development and Microsoft released Windows Me in its place.

Eventually “Neptune” was merged into their new project, Whistler, which later became Windows XP. Since then, a new business system, Windows Server 2003, has expanded the top end of the range, and the forthcoming Windows Vista will complete it. Windows CE, Microsoft’s offering in the mobile and embedded markets, is also a true 32-bit operating system.

With the introduction of IA-64 arhitecture (derived from Itanium, as the processor) and later the AMD64 architecture (developed by AMD as a superset of the x86 architecture), Microsoft launched new versions of Operating System for them. These new versions were Windows XP 64-bit Edition (for IA-64 systems and for AMD64 systems) and Windows Server 2003, in versions for both IA-64 and AMD64. The date when Microsoft released the AMD64 version for both Windows XP and Server 2003 was April 25, 2005.

And now let’s look at the latest Microsoft Windows version.

Prior to the announcement of the Vista name on July 22, 2005, it was known by its codename Longhorn, after the Longhorn Saloon, a popular bar in Whistler, British Columbia.

Microsoft’s primary stated goal with Vista, however, has been to improve the state of security in the Windows operating system. Amongst the many common criticisms of Windows XP, the most significant has been its commonly exploited security vulnerabilities, and an overall susceptibility to malware, viruses and buffer overflows. In light of this, Microsoft chairman Bill Gates announced in early 2002 a company-wide ‘Trustworthy Computing initiative’ which aims to incorporate security work into every aspect of software development at the company. Microsoft claimed it prioritized improving the security of Windows XP and Windows Server 2003 above finishing Windows Vista, which has significantly delayed its completion.

Microsoft first talked about “Longhorn” in July 2001, even before Windows XP’s release in October of that year. It was originally expected to ship sometime late in 2003 as a minor step between Windows XP and “Blackcomb” (now known as Windows “Vienna”). Gradually, “Longhorn” assimilated many important new features and technologies of “Blackcomb”, and so the date of release was pushed back a few times. Faced with ongoing delays and concerns about feature creep, Microsoft announced on August 27, 2004 that it was making significant changes. “Longhorn” development basically started afresh, building on the Windows Server 2003 codebase, and re-incorporating only the features that would be intended for an actual operating system release. Some previously-announced features, such as WinFS, were dropped.

After “Longhorn” was renamed to Windows Vista, an unprecedented beta-test program was started, which has involved hundreds of thousands of volunteers and companies. In September 2005, Microsoft started releasing regular Community Technology Previews (CTP) to beta testers. The first of these was build 5219, distributed among 2005 PDC attendees, and has been released to Microsoft Beta testers and MSDN subscribers. Subsequent CTPs have introduced most of the planned features for the final product, as well as a number of changes to the user interface, based in large part on feedback from beta testers. Windows Vista was deemed feature-complete with the release of build 5308 CTP, released on February 22, 2006, and much of the remainder of work between that build and the final release of the product will focus on stability, performance, application and driver compatibility, and documentation. Jim Allchin stated in an interview there will be no “Release Candidates” as with previous versions of Windows; they will instead continue shipping CTPs until the product is ready. However, Microsoft is hinting on the fact that there will be release candidates for Windows Vista by promising a Release Candidate 1 DVD kit when it becomes available for those who order the Beta 2 kit on DVD, instead of downloading.

After all these CTP, Microsoft released a Windows Vista Beta 2 on May 23, 2006 but only on June 7 Microsoft allowed everyone to download and to test it.

And here comes the real thing.