Windows 95

The "Start" button made its debut in Windows 95.

Windows 95 (codename Chicago) is a hybrid 16-bit/32-bit graphical operating system released on August 24, 1995 by the Microsoft Corporation.

Windows 95 is a direct descendant of Microsoft's formerly separate MS-DOS and Windows products. It is the first in that line without support for older, 16-bit x86 processors, thus requiring an Intel 80386 (or compatible) processor running in protected mode. It featured significant improvements to the GUI and underlying workings, including support for 256-character mixed-case long filenames and preemptively-multitasked protected-mode 32-bit applications.

Windows 95 ran on MS-DOS 6.22 (and later releases on MS-DOS 7.0), which was included (but generally hidden from the user). Windows 95 was the first Windows product to be tied to a specific version of DOS; this was seen as a way to leverage the dominant position Windows 3.1 had established in the GUI market and ensure that no non-Microsoft product would be able to provide the underlying operating system services.

The introduction of 32-bit file access in Windows for Workgroups 3.11 meant that 16-bit real mode MS-DOS was no longer used for managing the files while Windows was running, and the earlier introduction of the 32-bit disk access meant that PC BIOS wasn't used for managing hard disks. This essentially reduced MS-DOS to the role of a boot loader for the protected-mode Windows kernel. DOS could still be used for running old-style drivers for compatibility, but Microsoft discouraged using them, as this prevented proper multitasking and impaired system stability. The Control Panel allowed a user to see what MS-DOS components were still used by the system; optimal performance was achieved when they were all bypassed. The Windows kernel still used MS-DOS drivers in the so-called Safe mode, but this mode existed merely to allow a user to fix problems with loading native, protected-mode drivers.

32-bit file access was necessary for the long file names feature introduced with Windows 95 through the use of the VFAT file system (a variant of FAT16). It was available to both Windows programs and MS-DOS programs started from Windows (they had to be adapted slightly, since accessing long file names required using larger pathname buffers and hence different system calls). Competing DOS-compatible operating systems needed an upgrade to be able to see these names. Using older versions of DOS utilities to manipulate files meant that the long names were not visible and would be lost if files were copied or moved around. During a Windows 95 automatic upgrade of an older Windows 3.1 system, DOS and third party disk utilities which could destroy long file names were identified and made unavailable. If the need arose to depend on disk utilities that do not recognise long file names, such as MS-DOS 6.22's defrag utility, a program was provided on the CD-ROM called LFNBACK for backup and restoration of long file names. The program is in the \ADMIN\APPTOOLS\LFNBACK directory of the Windows 95 CD-ROM.

Windows 95 brought much greater power and usability to the desktop GUI, and also ended competition in the desktop operating system market. While it was technically possible (but not a good idea given the above) to start the Windows 95 kernel and GUI from DR-DOS - and probably PC-DOS too - this did not emerge in court until some years later, by which time the other major players in the DOS market were effectively out of business. In the marketplace, Windows 95 was an unqualified success, and within a year or two of its release had become the most successful operating system ever made.

Windows 95 was released with great fanfare, including a commercial featuring the Rolling Stones song "Start Me Up" (a reference to the Start button). Microsoft's advertising campaign featured stories of people waiting in line outside stores to get a copy, and there were tales of people without computers buying the software on hype alone, not even knowing what Windows was.

The release of Windows 95 coincided with a general movement of computing into the mainstream, largely fueled by a dramatic drop in hardware prices, in particular, by the end of Intel's long-held near-monopoly on CPU production with the entry of fast, low-cost parts from AMD and Cyrix.

Windows 95 marked the introduction of the "Start" button and taskbar to the mass-market desktop PC (although similar GUI features had been used for some years in desktop computers by Acorn's Arthur and RISC OS operating systems, the market for those systems was extremely restricted). These have remained staple features of all subsequent versions of Windows, and were later copied in other desktop environments.

Later editions of Windows 95 (OSR 1 (Version 4.00 build 989), OSR 2 (Version 4.00 build 1111), OSR 2.1 (Version 4.03 build 1212), OSR 2.5 (Version 4.03 build 1214)) that were available only to OEMs came with Internet Explorer 3 and Windows 95 OSR 2.5 came with Internet Explorer 4 preinstalled. Internet Explorer 4 introduced several changes to some aspects of the GUI when it was integrated into the operating system. Internet Explorer was then used to render the desktop and window contents using HTML. This was a focal point in Microsoft's antitrust lawsuit, as an integrated Explorer edged out competitor Netscape's product. All the later releases introduced also support for FAT32 file-system and a version 7.0 of MS-DOS.

Windows 95 has been superseded by Windows 98, Windows 98 Second Edition, Windows Me, Windows 2000, and Windows XP. The Windows NT-based kernel used in Windows 2000 and Windows XP has shown itself to be much more robust and powerful than its predecessor in Windows 95, Windows 98, and Windows ME. As a result, those versions of Windows are being phased out. As of December 31, 2002, Microsoft ended its support for Windows 95.

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