Windows 95

The initial design and planning of Windows 95 can be traced back to around March 1992,[6][7][8] just around the time before the release of Windows 3.1. At this time, Windows for Workgroups 3.11 and Windows NT 3.1 were still in development and Microsoft's plan for the future was focused on Cairo. Cairo would be Microsoft's next-generation operating system based on Windows NT, featuring a new user interface and an object-based file system, but it was not planned to be shipped before 1994. However, Cairo would partially ship in late July 1996 in the form of Windows NT 4.0, but without the object-based file system, which would later evolve into WinFS.

Simultaneously with Windows 3.1's release, IBM started shipping OS/2 2.0. Microsoft realized they were in need of an updated version of Windows that could support 32-bit applications and preemptive multitasking, but could still run on low-end hardware (Windows NT did not). So the development of Windows "Chicago" was started and, as it was planned for a late 1993 release, became known as Windows 93 which was also known as Windows 4.0. Initially, the decision was made not to include a new user interface, as this was planned for Cairo, and only focus on making installation, configuration, and networking easier. Windows 93 would ship together with MS-DOS 7.0, offering a more integrated experience to the user and making it pointless for the user to buy a DOS clone; this anti-competitive practice was denounced in Caldera v. Microsoft. MS-DOS 7.0 was in development at that time under the code name "Jaguar" and could optionally run on top of a Windows 3.1-based 32-bit protected-mode kernel called "Cougar" in order to better compete with DR-DOS. The first version of Chicago's feature specification was finished on September 30, 1992. Cougar was to become Chicago's kernel.

Architectural diagram

Windows 95 was designed to be maximally compatible with existing MS-DOS and 16-bit Windows programs and device drivers while offering a more stable and better performing system.[12][13] The Windows 95 architecture is an evolution of Windows for Workgroups' 386 enhanced mode. The lowest level of the operating system consists of a large number of virtual device drivers (VxDs) running in 32-bit protected mode and one or more virtual DOS machines running in virtual 8086 mode. The virtual device drivers are responsible for handling physical devices (such as video and network cards), emulating virtual devices used by the virtual machines or providing various system services. The three most important virtual device drivers are:

Virtual Machine Manager (VMM32.VXD)

Responsible for memory management, event handling, interrupt handling, loading and initializing virtual device drivers, creating new virtual machines and thread scheduling.[14]

Configuration Manager (CONFIGMG)

Responsible for implementing Plug and Play functionality; monitoring hardware configuration changes; detecting devices using bus enumerators; and allocating I/O ports, IRQs, DMA channels and memory in a conflict-free fashion.[15]

Installable File System Manager (Input/Output Subsystem)

Coordinates access to supported file systems. Windows 95 initially shipped with support for FAT12, FAT16, the VFAT extension, ISO 9660 (CDFS), Joliet and network redirectors, with later releases supporting FAT32.[16]

Access requests to physical media are sent to Input/Output Supervisor, a component responsible for scheduling the requests. Each physical media has its own device driver: access to the disk is performed by a port driver, while access to a SCSI device is handled by a miniport driver working atop the SCSI layer. Port and miniport drivers perform I/O operations in 32-bit protected mode, bypassing MS-DOS and BIOS, giving a significant performance improvement. In case there is no native Windows driver for a certain storage device, or if a device is forced to run in compatibility mode, the Real Mode Mapper can access it through MS-DOS.[17]

32-bit Windows programs are assigned their own memory segments, which can be adjusted to any desired size. Memory area outside the segment cannot be accessed by a program. If a program crashes, nothing else is harmed. Before this, programs used fixed non-exclusive 64 KB segments. While the 64 KB size was a serious handicap in DOS and Windows 3.x, lack of guarantee of exclusiveness was the cause of stability issues because programs sometimes overwrote each other's segments. A crashing Windows 3.x program could knock out surrounding processes.

The Win32 API is implemented by three modules, each consisting of a 16-bit and a 32-bit component:

Kernel

Provides high level access to memory and process management, and access to the file system. Consists of KRNL386.EXE, KERNEL32.DLL, and VWIN32.VXD.

User

Responsible for managing and drawing the various user interface components, such as windows, menus and buttons. Consists of USER.EXE and USER32.DLL.

Graphics Device Interface (GDI)

Responsible for drawing graphics in a device-independent way. Consists of GDI.EXE and GDI32.DLL.

Dependence on MS-DOS

Main article: MS-DOS 7

command.com running in a Windows console on Windows 95 (MS-DOS Prompt)

To end-users, MS-DOS appears as an underlying component of Windows 95. For example, it is possible to prevent the loading of the graphical user interface and boot the system into a real-mode MS-DOS environment. This was done by inserting command.com in the autoexec.bat file or changing the BootGUI variable in the MSDOS.SYS file to 0. This sparked debate amongst users and professionals regarding the extent to which Windows 95 is an operating system or merely a graphical shell running on top of MS-DOS.[18][19][17]

When the graphical user interface is started, the virtual machine manager takes over the filesystem-related and disk-related functionality. MS-DOS itself is demoted to a compatibility layer for 16-bit device drivers.[20] This contrasts with earlier versions of Windows which rely on MS-DOS to perform file and disk access (Windows for Workgroups 3.11 could also largely bypass MS-DOS when 32-bit file access and 32-bit disk access were enabled). Keeping MS-DOS in memory allows Windows 95 to use DOS device drivers when suitable Windows drivers are unavailable. Windows 95 is capable of using all 16-bit Windows 3.x drivers.

Unlike Windows 3.1x, DOS programs running in Windows 95 do not need DOS drivers for the mouse, CD-ROM and sound card; Windows drivers are used instead. HIMEM.SYS is still required to boot Windows 95. EMM386 and other memory managers, however, are only used by DOS programs. In addition, CONFIG.SYS and AUTOEXEC.BAT settings (aside from HIMEM.SYS) have no effect on Windows programs. DOS games, which could not be executed on Windows 3.x, can run inside Windows 95 (games tended to lock up Windows 3.x or cause other problems). As with Windows 3.x, DOS programs that use EGA or VGA graphics modes run in windowed mode (CGA and text mode programs can continue to run).[17]

On startup, the MS-DOS component in Windows 95 responds to a pressed F8 key by temporarily pausing the default boot process and presenting the DOS boot options menu, allowing the user to continue starting Windows normally, start Windows in safe mode or exit to the DOS prompt.[18] As in previous versions of MS-DOS, there is no 32-bit support and DOS drivers must be loaded for mice and other hardware.

As a consequence of being DOS-based, Windows 95 has to keep internal DOS data structures synchronized with those of Windows 95. When starting a program, even a native 32-bit Windows program, MS-DOS momentarily executes to create a data structure known as the Program Segment Prefix. It is even possible for MS-DOS to run out of conventional memory while doing so, preventing the program from launching.[18] Windows 3.x allocated fixed segments in conventional memory first. Since the segments were allocated as fixed, Windows could not move them, which would prevent any more programs from launching.

Microsoft partially removed support for File Control Blocks (an API hold-over of DOS 1.x and CP/M) in Windows 95 OSR2 (OEM Service Release 2). FCB functions can read FAT32 volumes, but not write to them.

Windows 95 introduced a redesigned shell based around a desktop metaphor; File shortcuts (also known as shell links) were introduced [21] and the desktop was re-purposed to hold shortcuts to applications, files and folders, reminiscent of Mac OS.

In Windows 3.1 the desktop was used to display icons of running applications. In Windows 95, the currently running applications were displayed as buttons on a taskbar across the bottom of the screen.[22] The taskbar also contained a notification area used to display icons for background applications, a volume control and the current time.[23]

The Start menu, invoked by clicking the "Start" button on the taskbar or by pressing the Windows key, was introduced as an additional means of launching applications or opening documents. While maintaining the program groups used by its predecessor Program Manager, it also displayed applications within cascading sub-menus.[24]

The previous File Manager program was replaced by Windows Explorer and the Explorer-based Control Panel and several other special folders were added such as My Computer, Dial Up Networking, Recycle Bin, Network Neighborhood, My Documents, Recent documents, Fonts, Printers, and My Briefcase among others. AutoRun was introduced for CD drives.

The user interface looked dramatically different from prior versions of Windows, but its design language did not have a special name like Metro, Aqua or Material Design. Internally it was called "the new shell" and later simply "the shell".[25] The subproject within Microsoft to develop the new shell was internally known as "Stimpy".[26]

In 1994, Microsoft designers Mark Malamud and Erik Gavriluk approached Brian Eno to compose music for the Windows 95 project.[27] The result was the six-second start-up music-sound of the Windows 95 operating system, The Microsoft Sound and it was first released as a startup sound in May 1995 on Windows 95 May Test Release build 468.[28]

When released for Windows 95 and Windows NT 4.0, Internet Explorer 4 came with an optional Windows Desktop Update, which modified the shell to provide several additional updates to Windows Explorer, including a Quick Launch toolbar, and new features integrated with Internet Explorer, such as Active Desktop (which allowed Internet content to be displayed directly on the desktop).

Some of the user interface elements introduced in Windows 95, such as the desktop, taskbar, Start menu and Windows Explorer file manager, remained fundamentally unchanged on future versions of Windows.

Windows 95 included support for 255-character mixed-case long filenames[29] and preemptively multitasked protected-mode 32-bit applications. 16-bit processes were still co-operatively multitasked.

Official system requirements were an Intel 80386DX CPU of any speed, 4 MB of system RAM and 50–55 MB of hard disk space depending on features selected. These minimal claims were made in order to maximize the available market of Windows 3.1 migrations. This configuration would rely heavily on virtual memory and was only optimal for productive use on single-tasking dedicated workstations.[30] It was possible to run Windows 95 on a 386 SX, but this led to even less acceptable performance due to its 16-bit external data bus. To achieve optimal performance, Microsoft recommended an Intel 80486 or compatible CPU with at least 8 MB of RAM.[31]

Windows 95 may fail to boot on computers with more than approximately 480 MB of memory.[32][33][34] In such a case, reducing the file cache size or the size of video memory can help.[32] The theoretical maximum according to Microsoft is 2 GB.[35]

Most copies of Windows 95 were on CD-ROM, but a floppy version could also be had for older machines. The retail floppy disk version of Windows 95 came on 13 DMF formatted floppy disks, while OSR 2.1 doubled the floppy count to 26. Both versions exclude additional software that the CD-ROM version might have featured. Microsoft Plus! for Windows 95 was also available on floppy disks. DMF was a special 21-sector format that Microsoft used to store 1.68 MB on floppy disks rather than the usual 1.44 MB.

Windows 95 was superseded by Windows 98 and could still be directly upgraded by either Windows 2000 Professional[36] or Windows Me. Office 2000 is the last version of Microsoft Office to be compatible with Windows 95. Similarly, Windows Media Player 7.1, released in May 2001, and DirectX 8.0a, released in February 2001, are the last versions of Windows Media Player and DirectX available for Windows 95, respectively.

The Windows 95 release included a commercial featuring The Rolling Stones' 1981 single "Start Me Up" (a reference to the Start button).[38] It was widely reported that Microsoft paid the Rolling Stones between US$8 and US$14 million for the use of the song in the Windows 95 advertising campaign. However, Microsoft said that this was just a rumor spread by the band to increase their market value, and the company actually paid a fraction of that amount.[39] A 30-minute promotional video, labeled a "cyber sitcom," featuring Jennifer Aniston and Matthew Perry, was also released to showcase the features of Windows 95.[40] Microsoft's US$200 million advertising campaign featured stories of people waiting in line outside stores to get a copy.[41]

In the UK, the largest computer chain PC World received a large quantity of point-of-sale material; many branches opened at midnight to sell the first copies of the product. Copies of The Times were available for free, and Microsoft paid for 1.5 million issues (twice the daily circulation at the time).[42]

In the United States, the Empire State Building in New York City was lit to match the colors of the Windows logo.[4] In Canada, a 100 m (330 ft) banner was hung down the side of the CN Tower in Toronto.[43]

The release included a number of "Fun Stuff" items on the CD, including music videos of Edie Brickell's "Good Times"[44] and Weezer's "Buddy Holly," a trailer for the 1995 film Rob Roy and the computer game Hover![45]

Sales were strong, with one million copies shipped worldwide in just four days.[46] According to International Data Corporation, by the end of 1998, Windows 95 was the most used desktop OS with 57.4% of the marketshare, with its successor Windows 98 coming in second at 17.2%. Windows 95 also still sold more non-OEM copies to large customers in the month of May 1999, which analysts attributed to large companies opting to wait for the release of Windows 2000.[47]

On December 31, 2001, Microsoft ended its support for Windows 95, making it an "obsolete" product per the Microsoft Lifecycle Policy.[57]

Many features that have since become key components of the Microsoft Windows series, such as the Start menu and the taskbar, originated in Windows 95. Neil MacDonald, a Gartner analyst, said that Windows 95 "was a quantum leap in difference in technological capability and stability." Ina Fried of CNET said that "by the time Windows 95 was finally ushered off the market in 2001, it had become a fixture on computer desktops around the world."[42]

Even though support for Windows 95 has ended, the software has occasionally remained in use on legacy systems for various purposes. In addition, some video game enthusiasts choose to use Windows 95 for their legacy system to play old DOS games, although some other versions of Windows such as Windows 98 can also be used for this purpose.

• Windows 9x