Windows 9x
Encyclopedia
Windows 9x is a generic term referring to a series of Microsoft Windows
computer operating system
s produced since 1995, which were based on the original and later modified Windows 95
kernel. This includes all versions of Windows 95
, Windows 98
and often also Windows Me
.
Internal release versions for versions of Windows 9x are "4.x", where previous MS-DOS based versions of Windows used version numbers of 3.2 or less
. Windows NT used a similar but separate version number between 3.5 and 4.0. The first successor to Windows Me (with internal version 4.9), Windows XP
, used Version 5.1.
Windows 9x is predominantly known for its use in desktops
; in 1998 Windows made up 82% of operating system market share.
Most of the feature set and compatibility of the Windows 9x line of operating systems was merged with Windows NT
with the release of Windows XP
, which was the successor to both Windows 2000
and Windows Me
.
Windows 1.0 was not a complete operating system, but rather an "operating environment" that extended MS-DOS
, and shared the latter's inherent flaws and problems.
The second release of Microsoft Windows, version 2.0, came out on 9 December 1987, and used the real-mode
memory
model, which confined it to a maximum of 1 megabyte
of memory. In such a configuration, it could run under another multitasking system like DESQview
, which used the 286
Protected Mode
.
Microsoft Windows scored a significant success with Windows 3.0, released in 1990. In addition to improved capabilities given to native applications, Windows also allowed users to better multitask
older MS-DOS based software compared to Windows/386, thanks to the introduction of virtual memory
.
Microsoft developed Windows 3.1, which included several minor improvements to Windows 3.0, but primarily consisted of bugfixes and multimedia support. It also excluded support for Real mode, and only ran on an 80286 or better processor. Later Microsoft also released Windows 3.11, a touch-up to Windows 3.1 which included all of the patches and updates that followed the release of Windows 3.1 in 1992.
Meanwhile Microsoft continued to develop Windows NT. The main architect of the system was Dave Cutler
, one of the chief architects of VMS at Digital Equipment Corporation
(later purchased by Compaq
, now part of Hewlett-Packard
). Microsoft hired him in August 1988 to create a successor to OS/2
, but Cutler created a completely new system instead.
Microsoft announced at the conference its intentions to develop a successor to both Windows NT and Windows 3.1's replacement (Windows 95
, code-named Chicago), which would unify the two into one operating system. This successor was codenamed Cairo
. In hindsight, Cairo was a much more difficult project than Microsoft had anticipated and, as a result, NT and Chicago would not be unified until Windows XP
.
After Windows 3.11
, Microsoft began to develop a new consumer oriented version of the operating system code-named Chicago. Chicago was designed to have support for 32-bit preemptive multitasking like OS/2 and Windows NT, although a 16-bit kernel would remain for the sake of backward compatibility. The Win32 API
first introduced with Windows NT was adopted as the standard 32-bit programming interface, with Win16 compatibility being preserved through a technique known as "thunking". A new GUI was not originally planned as part of the release, although elements of the Cairo user interface were borrowed and added as other aspects of the release (notably Plug and Play) slipped.
Microsoft did not change all of the Windows code to 32-bit; parts of it remained 16-bit (albeit not directly using real mode
) for reasons of compatibility, performance and development time. Additionally it was necessary to carry over design decisions from earlier versions of Windows for reasons of backwards compatibility, even if these design decisions no longer matched a more modern computing environment. These factors eventually began to impact the operating system's efficiency and stability.
Microsoft marketing adopted Windows 95
as the product name for Chicago when it was released on August 24, 1995.
Microsoft went on to release five different versions of Windows 95:
OSR2, OSR2.1 and OSR2.5 were not released to the general public; rather, they were available only to OEMs
that would preload the OS onto computers. Some companies sold new hard drives with OSR2 preinstalled (officially justifying this as needed due to the hard drive's capacity).
The first Microsoft Plus!
add-on pack was sold for Windows 95.
On 25 June 1998, Microsoft released Windows 98. It included new hardware drivers and better support for the FAT32
file system which allows support for disk partitions larger than the 2 GB maximum accepted by Windows 95. The USB support in Windows 98 is more robust than the basic support provided by the OEM
editions of Windows 95. It also controversially integrated the Internet Explorer
browser into the Windows GUI and Windows Explorer file manager.
In 1999, Microsoft released Windows 98 Second Edition, an interim release whose notables features were the addition of Internet Connection Sharing
and improved WDM audio and modem support. Internet Connection Sharing is a form of network address translation
, allowing several machines on a LAN (Local Area Network) to share a single Internet connection. Windows 98 Second Edition has certain improvements over the original release. Hardware support through device drivers was increased. Many minor problems present in the original Windows 98 were found and fixed which make it, according to many, the most stable release of Windows 9x family—to the extent that commentators used to say that Windows 98's beta version was more stable than Windows 95's final (gamma) version.
In September 2000, Microsoft introduced Windows Me (Millennium Edition), which upgraded Windows 98 with enhanced multimedia and Internet features. It also introduced the first version of system restore
, which allowed users to revert their system state to a previous "known-good" point in the case of system failure. The first version of Windows Movie Maker
was introduced as well.
Windows Me was conceived as a quick one-year project that served as a stopgap release between Windows 98 and Windows XP. Many of the new features were available from the Windows Update site
as updates for older Windows versions. As a result, Windows Me was not acknowledged as a distinct operating system along the lines of 95 or 98, and is often included in the Windows 9x series.
Windows Me was criticized by users for its instability and unreliability, due to frequent freezes and crashes. A PC World article dubbed Windows Me the "Mistake Edition" and placed it 4th in their "Worst Tech Products of All Time" feature.
The inability of users to easily boot into MS-DOS mode, as in Windows 95 or 98, led users to quickly learn how to hack their Windows Me installations to provide the needed service.
The release of Windows XP signalled a change of direction for Microsoft, bringing the consumer and business Operating Systems together.
One by one, support for the Windows 9x series ended, and Microsoft stopped selling the software to end users, then later to OEMs. By March 2004, it was impossible to purchase any copy of any Windows in the 9x series.
Microsoft DirectX, a set of standard gaming APIs, stopped being updated on Windows 95 at Version 8.0a. Windows 98, ME, and XP stopped being updated at version 9, and DirectX 10 ships with and is only available with Windows Vista and later; previous versions of Windows are not able to officially run DirectX 10-exclusive applications.
Microsoft Internet Explorer 7
, the first major update for the aged and insecure Internet Explorer 6
in half a decade, was only available for Windows XP SP2 or later.
The growing number of important updates caused by the end of service life of these pieces of software have slowly made Windows 9x less and less practical for everyday use. Today, even open source projects such as Mozilla won't run on Windows 9x without rework.
Like most operating systems, Windows 9x consists of kernel space
and user space memory.
Although Windows 9x features memory protection
, it does not protect the first megabyte of memory from userland applications. This area of memory contains code critical to the functioning of the operating system, and by writing into this area of memory an application can crash
or freeze
the operating system. This was a source of instability as faulty applications could by accident write into this region and with that halt the operating system.
Windows 9x/Me set aside two blocks of 64 KB memory regions for GDI
and heap resources. By running multiple applications, applications with numerous GDI elements or by running applications over a long span of time, it could exhaust these memory areas. If free system resources dropped below 10%, Windows would become unstable and likely crash.
), the Configuration Manager, and in Windows 98 and later, the WDM
Driver Manager (NTKERN). As a 32-bit operating system, virtual memory space is 4 GiB
, divided into a lower 2 GiB for applications and an upper 2 GiB for kernel per process.
. Hardware-specific settings are also stored in the registry, and many device drivers use the registry to load configuration data. Previous versions of Windows used files such as AUTOEXEC.BAT
, CONFIG.SYS
, WIN.INI
, SYSTEM.INI
and other files with an .INI extension to maintain configuration settings. As Windows became more complex and incorporated more features, .INI files became too unwieldy for the limitations of the then-current FAT filesystem. Backwards-compatibility with .INI files was maintained until Windows XP succeeded the 9x and NT lines.
Although Microsoft discourages using .INI files in favor of Registry entries, a large number of applications (particularly 16-bit Windows-based applications) still use .INI files. Windows 9x supports .INI files solely for compatibility with those applications and related tools (such as setup programs). The AUTOEXEC.BAT and CONFIG.SYS files also still exist for compatibility with real-mode system components and to allow users to change certain default system settings such as the PATH environment variable.
The registry consists of two files: User.dat and System.dat. In Windows Me, Classes.dat was added.
protected mode
kernel at the core of Windows 9x. Its primary responsibility is to create, run, monitor and terminate virtual machine
s. The VMM provides services that manage memory, processes, interrupts and protection faults. The VMM works with virtual devices (loadable kernel modules, which consist mostly of 32-bit ring 0 or kernel mode code, but may include other types of code, such as a 16-bit real mode initialisation segment) to allow those virtual devices to intercept interrupts and faults to control the access that an application has to hardware devices and installed software. Both the VMM and virtual device drivers run in a single, 32-bit, flat model address space at privilege level 0 (also called ring 0). The VMM provides multi-threaded, preemptive multitasking. It runs multiple applications simultaneously by sharing CPU (central processing unit
) time between the threads in which the applications and virtual machines run.
The VMM is also responsible for creating MS-DOS environments for system processes and Windows applications that still need to run in MS-DOS mode. It is the replacement for Win386 in Windows 3.x, and the file vmm32.vxd is a compressed archive containing most of the core VxD, including VMM.vxd itself and ifsmgr.vxd (which facilitates file system access without the need to call the real mode file system code of the DOS kernel).
or HPFS, but there are third-party solutions which allow Windows 9x to have read-only access to NTFS volumes.
Early versions of Windows 95 did not support FAT32.
Like Windows for Workgroups 3.11, Windows 9x provides support for 32-bit file access
based on IFSHLP.SYS
, and unlike Windows 3.x, Windows 9x has support for the VFAT file system, allowing file names
with a maximum of 255 characters instead of having 8.3 filenames.
or error reporting
which the Windows NT family of operating systems has, although software like Norton CrashGuard can be used to achieve similar capabilities on Windows 9x.
file system
s (including FAT12/16/32), which are the only ones that Windows 9x supports officially, though Windows NT also supports FAT 12 and 16 (but not 32) and Windows 9x can be extended to read and write NTFS volumes using third-party Installable File System
drivers. FAT systems have very limited security; every user that has access to a FAT drive also has access to all files on that drive. The FAT file systems provide no access control list
s and file-system level encryption
like NTFS
.
Some operating systems that were available at the same time as Windows 9x are either multi-user
or have multiple user accounts with different access privileges, which allows important system files (such as the kernel image) to be immutable under most user accounts. In contrast, while Windows 95 and later operating systems offer the option of having profiles for multiple users, they have no concept of access privileges, making them roughly equivalent to a single-user, single-account operating system; this means that all processes
can modify all files on the system that aren't open, in addition to being able to modify the boot sector and perform other low-level hard drive modifications. This enables viruses and other clandestinely installed software to integrate themselves with the operating system in a way that is difficult for ordinary users to detect or undo. The profile support in the Windows 9x family is meant for convenience only; unless some registry keys are modified, the system can be accessed by pressing "Cancel" at login, even if all profiles have a password. Windows 95's default login dialog box also allows new user profiles to be created without having to log in first.
Users and software can render the operating system unable to function by deleting or overwriting important system files from the hard disk. Users and software are also free to change configuration files in such a way that the operating system is unable to boot or properly function.
Installation software often replaced and deleted system files without properly checking if the file was still in use or of a newer version. This created a phenomenon often referred to as DLL hell
.
Windows Me introduced System File Protection and System Restore
to handle common problems caused by this issue.
DOS
's FAT
and FAT32 filesystem inhereited by Windows 9x have neither file protection nor file permissions of NTFS
.
s in Windows 9x can be virtual device drivers or (starting with Windows 98) WDM drivers. VxDs usually have the filename extension
.vxd or .386, whereas WDM compatible drivers usually use the extension .sys
. The 32-bit VxD message server (msgsrv32) is a program that is able to load virtual device drivers (VxDs) at startup and then handle communication with the drivers. Additionally, the message server performs several background functions, including loading the Windows shell (such as Explorer.exe or Progman.exe).
Another type of device drivers are .DRV drivers. These drivers are loaded in user-mode, and are commonly used to control devices such as multimedia devices. To provide access to these devices, a dynamic link library is required (such as MMSYSTEM.DLL).
Drivers written for Windows 9x/Windows Me are loaded into the same address space as the kernel. This means that drivers can by accident or design overwrite critical sections of the operating system. Doing this can lead to system crashes, freezes and disk corruption. Faulty operating system drivers were a source of instability for the operating system.
Other monolithic
and hybrid kernel
s, like Linux
and Windows NT, are also susceptible to malfunctioning drivers impeding the kernel's operation.
Often the software developers of drivers and applications had insufficient experience with creating programs for the 'new' system, thus causing many errors which have been generally described as "system errors" by users, even if the error is not caused by parts of Windows or DOS. Microsoft has repeatedly redesigned the Windows Driver architecture since the release of Windows 95 as a result.
, Data Execution Prevention
, symmetric multiprocessing
or multi-core
processors.
Windows 9x has no native support for SATA
host bus adapters (and neither did Windows 2000 and Windows XP), or USB drives (except Windows Me). There are, however, many SATA-I controllers for which Windows-98/ME drivers exist. Hardware driver support for Windows 98/ME began to decline in 2005, most notably for motherboard chipsets and video cards.
Early versions of Windows 95 had no support for USB or AGP acceleration.
was able to reduce the role of MS-DOS
in Windows much further than had been done in Windows 3.1x
and earlier. According to Microsoft, MS-DOS served two purposes in Windows 95: as the boot loader, and as the 16-bit legacy device driver layer.
When Windows 95 started up, MS-DOS loaded, processed CONFIG.SYS, launched COMMAND.COM, ran AUTOEXEC.BAT and finally ran WIN.COM. The WIN.COM program used MS-DOS to load the virtual machine manager, read SYSTEM.INI, load the virtual device drivers, and then turn off any running copies of EMM386
and switch into protected mode. Once in protected mode, the virtual device drivers (VxD
s) transferred all state information from MS-DOS to the 32-bit file system manager, and then shut off MS-DOS. These VxDs allow Windows 9x to interact with hardware resources directly, as providing low-level functionalities such as 32-bit disk access
and memory management. All future file system operations would get routed to the 32-bit file system manager.
In Windows Me
, win.com was no longer executed during the startup process; instead it went directly to execute VMM32.VXD from IO.SYS.
The second role of MS-DOS (as the 16-bit legacy device driver layer) was as a backward compatibility tool for running DOS programs in Windows. Many MS-DOS programs and device drivers interacted with DOS in a low-level way; for example, by patching low-level BIOS interrupts such as int 13h
, the low-level disk I/O interrupt. When a program issued an int 21h call to access MS-DOS, the call would go first to the 32-bit file system manager, which would attempt to detect this sort of patching. If it detects that the program has tried to hook into DOS, it will jump back into the 16-bit code to let the hook run. A 16-bit driver called IFSMGR.SYS would previously have been loaded by CONFIG.SYS, the job of which was to hook MS-DOS first before the other drivers and programs got a chance, then jump from 16-bit code back into 32-bit code, when the DOS program had finished, to let the 32-bit file system manager continue its work. According to Windows developer Raymond Chen, "MS-DOS was just an extremely elaborate decoy. Any 16-bit drivers and programs would patch or hook what they thought was the real MS-DOS, but which was in reality just a decoy. If the 32-bit file system manager detected that somebody bought the decoy, it told the decoy to quack.
Having a command line mode outside of the GUI also offers the ability to fix certain system errors without entering the GUI. For example, if a virus is active in GUI mode it can often be safely removed in DOS mode, by deleting its files, which are usually locked while infected in Windows.
Similarly, corrupted registry files, system files or boot files can be restored from the command line. Windows 95 and Windows 98 can be started from DOS Mode by typing 'WIN' at the command prompt. However, the Recovery Console
for Windows 2000
, which as a version of Windows NT played a similar role in removing viruses.
Because DOS was not designed for multitasking purposes, Windows versions such as 9x that are DOS-based lack File System security, such as file permissions. Further, if the user uses 16-bit DOS drivers, Windows can become unstable. Hard disk errors often plague the Windows 9x series.
(or GUI). For desktop systems, the default mode is usually graphical user interface, where the CLI is available through MS-DOS
windows.
The graphical user interface
(GUI) runs on a DOS-based layer.
The GDI
, which is a part of the Win32 and Win16 subsystems, is also a module that is loaded in user mode, unlike Windows NT where the GDI is loaded in kernel mode.
Alpha compositing
and therefore transparency
effects, such as fade effects in menus, are not supported by the GDI in Windows 9x.
On desktop machines, Windows Explorer
is the default user interface, though a variety of additional Windows shell replacement exist.
Other GUIs include LiteStep
, bbLean
and Program Manager
. The GUI provides a means to control the placement and appearance of individual application windows, and interacts with the Window System.
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
computer operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s produced since 1995, which were based on the original and later modified Windows 95
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...
kernel. This includes all versions of Windows 95
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...
, Windows 98
Windows 98
Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid...
and often also Windows Me
Windows Me
Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....
.
Internal release versions for versions of Windows 9x are "4.x", where previous MS-DOS based versions of Windows used version numbers of 3.2 or less
Windows 3.x
Windows 3.x can refer to either an individual or all of the following versions of Microsoft Windows:*Windows 3.0*Windows 3.1x*Windows 3.2...
. Windows NT used a similar but separate version number between 3.5 and 4.0. The first successor to Windows Me (with internal version 4.9), Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
, used Version 5.1.
Windows 9x is predominantly known for its use in desktops
Desktop computer
A desktop computer is a personal computer in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Early desktop computers are designed to lay flat on the desk, while modern towers stand upright...
; in 1998 Windows made up 82% of operating system market share.
Most of the feature set and compatibility of the Windows 9x line of operating systems was merged with Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...
with the release of Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
, which was the successor to both Windows 2000
Windows 2000
Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...
and Windows Me
Windows Me
Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....
.
Windows prior to 95
The first independent version of Microsoft Windows, version 1.0, released on 20 November 1985, achieved little popularity. It was originally going to be called "Interface Manager" but Rowland Hanson, the head of marketing at Microsoft, convinced the company that the name Windows would be more appealing to consumers.Windows 1.0 was not a complete operating system, but rather an "operating environment" that extended MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
, and shared the latter's inherent flaws and problems.
The second release of Microsoft Windows, version 2.0, came out on 9 December 1987, and used the real-mode
Real mode
Real mode, also called real address mode, is an operating mode of 80286 and later x86-compatible CPUs. Real mode is characterized by a 20 bit segmented memory address space and unlimited direct software access to all memory, I/O addresses and peripheral hardware...
memory
Computer storage
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
model, which confined it to a maximum of 1 megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
of memory. In such a configuration, it could run under another multitasking system like DESQview
DESQview
DESQview was a text mode multitasking program developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s...
, which used the 286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...
Protected Mode
Protected mode
In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units...
.
Microsoft Windows scored a significant success with Windows 3.0, released in 1990. In addition to improved capabilities given to native applications, Windows also allowed users to better multitask
Computer multitasking
In computing, multitasking is a method where multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for...
older MS-DOS based software compared to Windows/386, thanks to the introduction of virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
.
Microsoft developed Windows 3.1, which included several minor improvements to Windows 3.0, but primarily consisted of bugfixes and multimedia support. It also excluded support for Real mode, and only ran on an 80286 or better processor. Later Microsoft also released Windows 3.11, a touch-up to Windows 3.1 which included all of the patches and updates that followed the release of Windows 3.1 in 1992.
Meanwhile Microsoft continued to develop Windows NT. The main architect of the system was Dave Cutler
Dave Cutler
David Neil Cutler, Sr. is an American software engineer, designer and developer of several operating systems including RSX-11M, VMS and VAXELN at Digital Equipment Corporation and Windows at Microsoft.- Personal history :...
, one of the chief architects of VMS at Digital Equipment Corporation
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
(later purchased by Compaq
Compaq
Compaq Computer Corporation is a personal computer company founded in 1982. Once the largest supplier of personal computing systems in the world, Compaq existed as an independent corporation until 2002, when it was acquired for US$25 billion by Hewlett-Packard....
, now part of Hewlett-Packard
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
). Microsoft hired him in August 1988 to create a successor to OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...
, but Cutler created a completely new system instead.
Microsoft announced at the conference its intentions to develop a successor to both Windows NT and Windows 3.1's replacement (Windows 95
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...
, code-named Chicago), which would unify the two into one operating system. This successor was codenamed Cairo
Cairo (operating system)
Cairo was the code name for a project at Microsoft from 1991 to 1996. Its charter was to build technologies for a next generation operating system that would fulfill Bill Gates' vision of "information at your fingertips." Cairo never shipped, although portions of its technologies have since...
. In hindsight, Cairo was a much more difficult project than Microsoft had anticipated and, as a result, NT and Chicago would not be unified until Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
.
Windows 95
Windows 3.1x
Windows 3.1x is a series of 16-bit operating systems produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during March 1992 as a successor to Windows 3.0...
, Microsoft began to develop a new consumer oriented version of the operating system code-named Chicago. Chicago was designed to have support for 32-bit preemptive multitasking like OS/2 and Windows NT, although a 16-bit kernel would remain for the sake of backward compatibility. The Win32 API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
first introduced with Windows NT was adopted as the standard 32-bit programming interface, with Win16 compatibility being preserved through a technique known as "thunking". A new GUI was not originally planned as part of the release, although elements of the Cairo user interface were borrowed and added as other aspects of the release (notably Plug and Play) slipped.
Microsoft did not change all of the Windows code to 32-bit; parts of it remained 16-bit (albeit not directly using real mode
Real mode
Real mode, also called real address mode, is an operating mode of 80286 and later x86-compatible CPUs. Real mode is characterized by a 20 bit segmented memory address space and unlimited direct software access to all memory, I/O addresses and peripheral hardware...
) for reasons of compatibility, performance and development time. Additionally it was necessary to carry over design decisions from earlier versions of Windows for reasons of backwards compatibility, even if these design decisions no longer matched a more modern computing environment. These factors eventually began to impact the operating system's efficiency and stability.
Microsoft marketing adopted Windows 95
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...
as the product name for Chicago when it was released on August 24, 1995.
Microsoft went on to release five different versions of Windows 95:
- Windows 95 - original release
- Windows 95 A - included Windows 95 OSR1 slipstreamedSlipstream (computing)In computer jargon, to slipstream updates, patches or service packs means to integrate them into the installation files of their original software, so that the resulting files will allow a direct installation of the updated software....
into the installation. - Windows 95 B - (OSR2) included several major enhancements, Internet ExplorerInternet ExplorerWindows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...
(IE) 3.0 and full FAT32File Allocation TableFile Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
file system support. - Windows 95 B USB - (OSR2.1) included basic USBUniversal Serial BusUSB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
support. - Windows 95 C - (OSR2.5) included all the above features, plus IE 4.0. This was the last 95 version produced.
OSR2, OSR2.1 and OSR2.5 were not released to the general public; rather, they were available only to OEMs
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
that would preload the OS onto computers. Some companies sold new hard drives with OSR2 preinstalled (officially justifying this as needed due to the hard drive's capacity).
The first Microsoft Plus!
Microsoft Plus!
Microsoft Plus! was a commercial operating system enhancement product by Microsoft. The last edition is the Plus! SuperPack, which includes an assortment of screensavers, themes, and games, as well as multimedia applications...
add-on pack was sold for Windows 95.
Windows 98
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
file system which allows support for disk partitions larger than the 2 GB maximum accepted by Windows 95. The USB support in Windows 98 is more robust than the basic support provided by the OEM
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
editions of Windows 95. It also controversially integrated the Internet Explorer
Internet Explorer
Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...
browser into the Windows GUI and Windows Explorer file manager.
In 1999, Microsoft released Windows 98 Second Edition, an interim release whose notables features were the addition of Internet Connection Sharing
Internet Connection Sharing
Internet Connection Sharing is the use of a device with Internet access such as 3G cellular service, broadband via Ethernet, or other Internet gateway as an access point for other devices...
and improved WDM audio and modem support. Internet Connection Sharing is a form of network address translation
Network address translation
In computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....
, allowing several machines on a LAN (Local Area Network) to share a single Internet connection. Windows 98 Second Edition has certain improvements over the original release. Hardware support through device drivers was increased. Many minor problems present in the original Windows 98 were found and fixed which make it, according to many, the most stable release of Windows 9x family—to the extent that commentators used to say that Windows 98's beta version was more stable than Windows 95's final (gamma) version.
Windows Me
System Restore
System Restore is a component of Microsoft's Windows Me, Windows XP, Windows Vista and Windows 7, but not Windows 2000, operating systems that allows for the rolling back of system files, registry keys, installed programs, etc., to a previous state in the event of system malfunction or failure.The...
, which allowed users to revert their system state to a previous "known-good" point in the case of system failure. The first version of Windows Movie Maker
Windows Movie Maker
Windows Movie Maker is a video creating/editing software application, included in Microsoft Windows Me, XP, and Vista. It contains features such as effects, transitions, titles/credits, audio track, timeline narration, and Auto Movie. New effects and transitions can be made and existing ones can be...
was introduced as well.
Windows Me was conceived as a quick one-year project that served as a stopgap release between Windows 98 and Windows XP. Many of the new features were available from the Windows Update site
Windows Update
Windows Update is a service provided by Microsoft that provides updates for the Microsoft Windows operating system and its installed components, including Internet Explorer...
as updates for older Windows versions. As a result, Windows Me was not acknowledged as a distinct operating system along the lines of 95 or 98, and is often included in the Windows 9x series.
Windows Me was criticized by users for its instability and unreliability, due to frequent freezes and crashes. A PC World article dubbed Windows Me the "Mistake Edition" and placed it 4th in their "Worst Tech Products of All Time" feature.
The inability of users to easily boot into MS-DOS mode, as in Windows 95 or 98, led users to quickly learn how to hack their Windows Me installations to provide the needed service.
Decline
The release of Windows 2000 marked a shift in the user experience between the Windows 9x series and the Windows NT series. Where NT4 suffered from a lack of USB support, Plug and Play support, and an aging, difficult to use, archaic-looking interface, Windows 2000 had a modern interface, and better USB and plug and play support than any version of Windows 9x.The release of Windows XP signalled a change of direction for Microsoft, bringing the consumer and business Operating Systems together.
One by one, support for the Windows 9x series ended, and Microsoft stopped selling the software to end users, then later to OEMs. By March 2004, it was impossible to purchase any copy of any Windows in the 9x series.
End of Service life
Microsoft continued to support the use of the Windows 9x series, however, until July 11, 2006, when extended support ended for the software.Microsoft DirectX, a set of standard gaming APIs, stopped being updated on Windows 95 at Version 8.0a. Windows 98, ME, and XP stopped being updated at version 9, and DirectX 10 ships with and is only available with Windows Vista and later; previous versions of Windows are not able to officially run DirectX 10-exclusive applications.
Microsoft Internet Explorer 7
Internet Explorer 7
Windows Internet Explorer 7 is a web browser released by Microsoft in October 2006. Internet Explorer 7 is part of a long line of versions of Internet Explorer and was the first major update to the browser in more than 5 years...
, the first major update for the aged and insecure Internet Explorer 6
Internet Explorer 6
Internet Explorer 6 is the sixth major revision of Internet Explorer, a web browser developed by Microsoft for Windows operating systems...
in half a decade, was only available for Windows XP SP2 or later.
The growing number of important updates caused by the end of service life of these pieces of software have slowly made Windows 9x less and less practical for everyday use. Today, even open source projects such as Mozilla won't run on Windows 9x without rework.
Kernel
Windows 9x is a series of hybrid 16/32-bit operating systems.Like most operating systems, Windows 9x consists of kernel space
Kernel (computing)
In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources...
and user space memory.
Although Windows 9x features memory protection
Memory protection
Memory protection is a way to control memory access rights on a computer, and is a part of most modern operating systems. The main purpose of memory protection is to prevent a process from accessing memory that has not been allocated to it. This prevents a bug within a process from affecting...
, it does not protect the first megabyte of memory from userland applications. This area of memory contains code critical to the functioning of the operating system, and by writing into this area of memory an application can crash
Crash (computing)
A crash in computing is a condition where a computer or a program, either an application or part of the operating system, ceases to function properly, often exiting after encountering errors. Often the offending program may appear to freeze or hang until a crash reporting service documents...
or freeze
Hang (computing)
In computing, a hang or freeze occurs when either a single computer program, or the whole system ceases to respond to inputs. In the most commonly encountered scenario, a workstation with a graphical user interface, all windows belonging to the frozen program become static, and though the mouse...
the operating system. This was a source of instability as faulty applications could by accident write into this region and with that halt the operating system.
User Mode
The user-mode parts of Windows 9x consist of three subsystems: the Win16 subsystem, the Win32 subsystem and MS-DOS.Windows 9x/Me set aside two blocks of 64 KB memory regions for GDI
Graphics Device Interface
The Graphics Device Interface is a Microsoft Windows application programming interface and core operating system component responsible for representing graphical objects and transmitting them to output devices such as monitors and printers....
and heap resources. By running multiple applications, applications with numerous GDI elements or by running applications over a long span of time, it could exhaust these memory areas. If free system resources dropped below 10%, Windows would become unstable and likely crash.
Kernel Mode
The kernel mode parts consist of the Virtual Machine Manager (VMM), the Installable File System Manager (IFSHLPIFSHLP.SYS
IFSHLP.SYS is an MS-DOS device driver included with Microsoft Windows. It enables Windows to make direct file system calls bypassing MS-DOS methods and use native 32-bit file access for both local and network devices...
), the Configuration Manager, and in Windows 98 and later, the WDM
Windows Driver Model
In computing, the Windows Driver Model — also known at one point as the Win32 Driver Model — is a framework for device drivers that was introduced with Windows 98 and Windows 2000 to replace VxD, which was used on older versions of Windows such as Windows 95 and Windows 3.1, as well...
Driver Manager (NTKERN). As a 32-bit operating system, virtual memory space is 4 GiB
Gib
Gib may refer to:* A castrated male cat or ferret* Gibibit , measurement unit of digitally stored computer information* Gibraltar, British overseas territory* Drywall, construction material...
, divided into a lower 2 GiB for applications and an upper 2 GiB for kernel per process.
Registry
Like Windows NT, Windows 9x stores user-specific and configuration-specific settings in a large information database called the Windows registryWindows registry
The Windows Registry is a hierarchical database that stores configuration settings and options on Microsoft Windows operating systems. It contains settings for low-level operating system components as well as the applications running on the platform: the kernel, device drivers, services, SAM, user...
. Hardware-specific settings are also stored in the registry, and many device drivers use the registry to load configuration data. Previous versions of Windows used files such as AUTOEXEC.BAT
AUTOEXEC.BAT
AUTOEXEC.BAT is a system file found originally on DOS-type operating systems. It is a plain-text batch file that is located in the root directory of the boot device...
, CONFIG.SYS
CONFIG.SYS
CONFIG.SYS is the primary configuration file for the DOS, OS/2 as well as similar operating systems. It is a special file that contains setup or configuration instructions for the computer system.- Usage :...
, WIN.INI
WIN.INI
WIN.INI is a basic INI file that was used in versions of the Microsoft Windows operating environment up to Windows 3.11 to store basic settings at boot time. By default, all font, communications drivers, wallpaper, screen saver, and language settings were stored in WIN.INI by Windows 3.x...
, SYSTEM.INI
SYSTEM.INI
SYSTEM.INI was an initialization used in early versions of Microsoft Windows to load device drivers and the default Windows shell , among other system settings. Many of these settings were honored in Windows 9x , although the INI files had begun to be phased out in favor of the Windows Registry...
and other files with an .INI extension to maintain configuration settings. As Windows became more complex and incorporated more features, .INI files became too unwieldy for the limitations of the then-current FAT filesystem. Backwards-compatibility with .INI files was maintained until Windows XP succeeded the 9x and NT lines.
Although Microsoft discourages using .INI files in favor of Registry entries, a large number of applications (particularly 16-bit Windows-based applications) still use .INI files. Windows 9x supports .INI files solely for compatibility with those applications and related tools (such as setup programs). The AUTOEXEC.BAT and CONFIG.SYS files also still exist for compatibility with real-mode system components and to allow users to change certain default system settings such as the PATH environment variable.
The registry consists of two files: User.dat and System.dat. In Windows Me, Classes.dat was added.
Virtual Machine Manager
The Virtual Machine Manager (VMM) is the 32-bit32-bit
The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....
protected mode
Protected mode
In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units...
kernel at the core of Windows 9x. Its primary responsibility is to create, run, monitor and terminate virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
s. The VMM provides services that manage memory, processes, interrupts and protection faults. The VMM works with virtual devices (loadable kernel modules, which consist mostly of 32-bit ring 0 or kernel mode code, but may include other types of code, such as a 16-bit real mode initialisation segment) to allow those virtual devices to intercept interrupts and faults to control the access that an application has to hardware devices and installed software. Both the VMM and virtual device drivers run in a single, 32-bit, flat model address space at privilege level 0 (also called ring 0). The VMM provides multi-threaded, preemptive multitasking. It runs multiple applications simultaneously by sharing CPU (central processing unit
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
) time between the threads in which the applications and virtual machines run.
The VMM is also responsible for creating MS-DOS environments for system processes and Windows applications that still need to run in MS-DOS mode. It is the replacement for Win386 in Windows 3.x, and the file vmm32.vxd is a compressed archive containing most of the core VxD, including VMM.vxd itself and ifsmgr.vxd (which facilitates file system access without the need to call the real mode file system code of the DOS kernel).
File Systems
Windows 9x does not natively support NTFSNTFS
NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7....
or HPFS, but there are third-party solutions which allow Windows 9x to have read-only access to NTFS volumes.
Early versions of Windows 95 did not support FAT32.
Like Windows for Workgroups 3.11, Windows 9x provides support for 32-bit file access
32-bit File Access
32-bit file access refers to the higher performance, protected mode disk caching method introduced in Windows for Workgroups 3.11, which replaced SmartDrive . It bypassed MS-DOS and directly accessed the disk, either via the BIOS or 32-bit disk access...
based on IFSHLP.SYS
IFSHLP.SYS
IFSHLP.SYS is an MS-DOS device driver included with Microsoft Windows. It enables Windows to make direct file system calls bypassing MS-DOS methods and use native 32-bit file access for both local and network devices...
, and unlike Windows 3.x, Windows 9x has support for the VFAT file system, allowing file names
Long filename
Long filenames , are Microsoft's way of implementing filenames longer than the 8.3 filename, or short-filename, naming scheme used in Microsoft DOS in their modern FAT and NTFS filesystems. Because these filenames can be longer than an 8.3 filename, they can be more descriptive...
with a maximum of 255 characters instead of having 8.3 filenames.
Event Logging and Tracing
Also, there is no support for event logging and tracingTracing (software)
In software engineering, tracing is a specialized use of logging to record information about a program's execution. This information is typically used by programmers for debugging purposes, and additionally, depending on the type and detail of information contained in a trace log, by experienced...
or error reporting
Windows Error Reporting
Windows Error Reporting is a crash reporting technology introduced by Microsoft with Windows XP and included in later Windows versions and Windows Mobile 5.0 and 6.0. Not to be confused with the Dr...
which the Windows NT family of operating systems has, although software like Norton CrashGuard can be used to achieve similar capabilities on Windows 9x.
Security
Windows 9x is designed as a single-user system. Thus, the security model is much less effective than the one in Windows NT. One reason for this is the FATFile Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
s (including FAT12/16/32), which are the only ones that Windows 9x supports officially, though Windows NT also supports FAT 12 and 16 (but not 32) and Windows 9x can be extended to read and write NTFS volumes using third-party Installable File System
Installable File System
The Installable File System is a filesystem API in IBM OS/2 and Microsoft Windows that enables the operating system to recognize and load drivers for file systems...
drivers. FAT systems have very limited security; every user that has access to a FAT drive also has access to all files on that drive. The FAT file systems provide no access control list
Access control list
An access control list , with respect to a computer file system, is a list of permissions attached to an object. An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects. Each entry in a typical ACL specifies a subject...
s and file-system level encryption
Encrypting File System
The Encrypting File System on Microsoft Windows is a feature introduced in version 3.0 of NTFS that provides filesystem-level encryption...
like NTFS
NTFS
NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7....
.
Some operating systems that were available at the same time as Windows 9x are either multi-user
Multi-user
Multi-user is a term that defines an operating system or application software that allows concurrent access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving the...
or have multiple user accounts with different access privileges, which allows important system files (such as the kernel image) to be immutable under most user accounts. In contrast, while Windows 95 and later operating systems offer the option of having profiles for multiple users, they have no concept of access privileges, making them roughly equivalent to a single-user, single-account operating system; this means that all processes
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
can modify all files on the system that aren't open, in addition to being able to modify the boot sector and perform other low-level hard drive modifications. This enables viruses and other clandestinely installed software to integrate themselves with the operating system in a way that is difficult for ordinary users to detect or undo. The profile support in the Windows 9x family is meant for convenience only; unless some registry keys are modified, the system can be accessed by pressing "Cancel" at login, even if all profiles have a password. Windows 95's default login dialog box also allows new user profiles to be created without having to log in first.
Users and software can render the operating system unable to function by deleting or overwriting important system files from the hard disk. Users and software are also free to change configuration files in such a way that the operating system is unable to boot or properly function.
Installation software often replaced and deleted system files without properly checking if the file was still in use or of a newer version. This created a phenomenon often referred to as DLL hell
DLL hell
In computing, DLL Hell is a term for the complications that arise when working with dynamic link libraries used with Microsoft Windows operating systems, particularly legacy 16-bit editions which all run in a single memory space....
.
Windows Me introduced System File Protection and System Restore
System Restore
System Restore is a component of Microsoft's Windows Me, Windows XP, Windows Vista and Windows 7, but not Windows 2000, operating systems that allows for the rolling back of system files, registry keys, installed programs, etc., to a previous state in the event of system malfunction or failure.The...
to handle common problems caused by this issue.
DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
's FAT
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
and FAT32 filesystem inhereited by Windows 9x have neither file protection nor file permissions of NTFS
NTFS
NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7....
.
Network Sharing
Windows 9x offers share-level access control security for file and printer sharing as well as user-level access control if a Windows NT based operating system is available on the network. In contrast, Windows NT-based operating systems offer only user-level access control but integrated with the operating system's own user account security mechanism.Drivers
Device driverDevice driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
s in Windows 9x can be virtual device drivers or (starting with Windows 98) WDM drivers. VxDs usually have the filename extension
Filename extension
A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....
.vxd or .386, whereas WDM compatible drivers usually use the extension .sys
.sys
.sys is a filename extension in Microsoft Windows and DOS-type operating system.Most .sys files are real-mode device drivers. Certain files using this extension are not, however: MSDOS.SYS and IO.SYS are core operating system files in MS-DOS and Windows 9x...
. The 32-bit VxD message server (msgsrv32) is a program that is able to load virtual device drivers (VxDs) at startup and then handle communication with the drivers. Additionally, the message server performs several background functions, including loading the Windows shell (such as Explorer.exe or Progman.exe).
Another type of device drivers are .DRV drivers. These drivers are loaded in user-mode, and are commonly used to control devices such as multimedia devices. To provide access to these devices, a dynamic link library is required (such as MMSYSTEM.DLL).
Drivers written for Windows 9x/Windows Me are loaded into the same address space as the kernel. This means that drivers can by accident or design overwrite critical sections of the operating system. Doing this can lead to system crashes, freezes and disk corruption. Faulty operating system drivers were a source of instability for the operating system.
Other monolithic
Monolithic kernel
A monolithic kernel is an operating system architecture where the entire operating system is working in the kernel space and alone as supervisor mode...
and hybrid kernel
Hybrid kernel
A hybrid kernel is a kernel architecture based on combining aspects of microkernel and monolithic kernel architectures used in computer operating systems. The category is controversial due to the similarity to monolithic kernel; the term has been dismissed by Linus Torvalds as simple marketing...
s, like Linux
Linux kernel
The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
and Windows NT, are also susceptible to malfunctioning drivers impeding the kernel's operation.
Often the software developers of drivers and applications had insufficient experience with creating programs for the 'new' system, thus causing many errors which have been generally described as "system errors" by users, even if the error is not caused by parts of Windows or DOS. Microsoft has repeatedly redesigned the Windows Driver architecture since the release of Windows 95 as a result.
CPU & Bus Technologies
Windows 9x has no native support for hyper-threadingHyper-threading
Hyper-threading is Intel's term for its simultaneous multithreading implementation in its Atom, Intel Core i3/i5/i7, Itanium, Pentium 4 and Xeon CPUs....
, Data Execution Prevention
Data Execution Prevention
Data Execution Prevention is a security feature included in modern operating systems.It is known to be available in Linux, Mac OS X, and Microsoft Windows operating systems and is intended to prevent an application or service from executing code from a non-executable memory region. This helps...
, symmetric multiprocessing
Symmetric multiprocessing
In computing, symmetric multiprocessing involves a multiprocessor computer hardware architecture where two or more identical processors are connected to a single shared main memory and are controlled by a single OS instance. Most common multiprocessor systems today use an SMP architecture...
or multi-core
Multi-core (computing)
A multi-core processor is a single computing component with two or more independent actual processors , which are the units that read and execute program instructions...
processors.
Windows 9x has no native support for SATA
Serial ATA
Serial ATA is a computer bus interface for connecting host bus adapters to mass storage devices such as hard disk drives and optical drives...
host bus adapters (and neither did Windows 2000 and Windows XP), or USB drives (except Windows Me). There are, however, many SATA-I controllers for which Windows-98/ME drivers exist. Hardware driver support for Windows 98/ME began to decline in 2005, most notably for motherboard chipsets and video cards.
Early versions of Windows 95 had no support for USB or AGP acceleration.
MS-DOS
Windows 95Windows 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...
was able to reduce the role of MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
in Windows much further than had been done in Windows 3.1x
Windows 3.1x
Windows 3.1x is a series of 16-bit operating systems produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during March 1992 as a successor to Windows 3.0...
and earlier. According to Microsoft, MS-DOS served two purposes in Windows 95: as the boot loader, and as the 16-bit legacy device driver layer.
When Windows 95 started up, MS-DOS loaded, processed CONFIG.SYS, launched COMMAND.COM, ran AUTOEXEC.BAT and finally ran WIN.COM. The WIN.COM program used MS-DOS to load the virtual machine manager, read SYSTEM.INI, load the virtual device drivers, and then turn off any running copies of EMM386
EMM386
The name EMM386 was used for the expanded memory managers of both Microsoft's MS-DOS and Digital Research's DR-DOS, which created expanded memory using extended memory on Intel 80386 CPUs. There also is an EMM386.EXE available in FreeDOS....
and switch into protected mode. Once in protected mode, the virtual device drivers (VxD
VxD
VxD is the device driver model used in Microsoft Windows/386, the 386 enhanced mode of Windows 3.x, Windows 9x, and to some extend also by the Novell DOS 7, OpenDOS 7.01, and DR-DOS 7.02 multitasker...
s) transferred all state information from MS-DOS to the 32-bit file system manager, and then shut off MS-DOS. These VxDs allow Windows 9x to interact with hardware resources directly, as providing low-level functionalities such as 32-bit disk access
32-bit Disk Access
32-bit Disk Access refers to a special disk access and caching mode available in older, MS-DOS-based Microsoft Windows operating systems. It was a set of protected mode device drivers that worked together to enhance the system's BIOS...
and memory management. All future file system operations would get routed to the 32-bit file system manager.
In Windows Me
Windows Me
Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....
, win.com was no longer executed during the startup process; instead it went directly to execute VMM32.VXD from IO.SYS.
The second role of MS-DOS (as the 16-bit legacy device driver layer) was as a backward compatibility tool for running DOS programs in Windows. Many MS-DOS programs and device drivers interacted with DOS in a low-level way; for example, by patching low-level BIOS interrupts such as int 13h
INT 13
INT 13H or INT 19 is shorthand for BIOS interrupt call 13hex, the 20th interrupt vector in an x86-based computer system. The BIOS typically sets up a real mode interrupt handler at this vector that provides sector-based hard disk and floppy disk read and write services using cylinder-head-sector ...
, the low-level disk I/O interrupt. When a program issued an int 21h call to access MS-DOS, the call would go first to the 32-bit file system manager, which would attempt to detect this sort of patching. If it detects that the program has tried to hook into DOS, it will jump back into the 16-bit code to let the hook run. A 16-bit driver called IFSMGR.SYS would previously have been loaded by CONFIG.SYS, the job of which was to hook MS-DOS first before the other drivers and programs got a chance, then jump from 16-bit code back into 32-bit code, when the DOS program had finished, to let the 32-bit file system manager continue its work. According to Windows developer Raymond Chen, "MS-DOS was just an extremely elaborate decoy. Any 16-bit drivers and programs would patch or hook what they thought was the real MS-DOS, but which was in reality just a decoy. If the 32-bit file system manager detected that somebody bought the decoy, it told the decoy to quack.
MS-DOS Virtualization
Windows 9x can run MS-DOS applications within itself using a method called "Virtualization", where an application is run on a "Virtual DOS Machine".MS-DOS Mode
Windows 95 and Windows 98 also offer regressive support for DOS applications in the form of being able to boot into a native "DOS Mode" (MS-DOS can be booted without booting Windows, not putting the CPU in protected mode). Through Windows 9x's memory managers and other post-DOS improvements, the overall system performance and functionality is improved. This differs from the emulation used in Windows NT-based operating systems. Some old applications or games may not run properly in a DOS box within Windows and require real DOS Mode.Having a command line mode outside of the GUI also offers the ability to fix certain system errors without entering the GUI. For example, if a virus is active in GUI mode it can often be safely removed in DOS mode, by deleting its files, which are usually locked while infected in Windows.
Similarly, corrupted registry files, system files or boot files can be restored from the command line. Windows 95 and Windows 98 can be started from DOS Mode by typing 'WIN'
Recovery Console
The Recovery Console is a feature of the Windows 2000, Windows XP and Windows Server 2003 operating systems. It provides the means for administrators to perform a limited range of tasks using a command line interface. Its primary function is to enable administrators to recover from situations...
for Windows 2000
Windows 2000
Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...
, which as a version of Windows NT played a similar role in removing viruses.
Because DOS was not designed for multitasking purposes, Windows versions such as 9x that are DOS-based lack File System security, such as file permissions. Further, if the user uses 16-bit DOS drivers, Windows can become unstable. Hard disk errors often plague the Windows 9x series.
User interface
Users can control a Windows 9x-based system through a command line interface (or CLI), or a graphical user interfaceGraphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
(or GUI). For desktop systems, the default mode is usually graphical user interface, where the CLI is available through MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
windows.
The graphical user interface
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
(GUI) runs on a DOS-based layer.
The GDI
Graphics Device Interface
The Graphics Device Interface is a Microsoft Windows application programming interface and core operating system component responsible for representing graphical objects and transmitting them to output devices such as monitors and printers....
, which is a part of the Win32 and Win16 subsystems, is also a module that is loaded in user mode, unlike Windows NT where the GDI is loaded in kernel mode.
Alpha compositing
Alpha compositing
In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial or full transparency. It is often useful to render image elements in separate passes, and then combine the resulting multiple 2D images into a single, final image in a...
and therefore transparency
Transparency (graphic)
Transparency is possible in a number of graphics file formats. The term transparency is used in various ways by different people, but at its simplest there is "full transparency" i.e. something that is completely invisible. Of course, only part of a graphic should be fully transparent, or there...
effects, such as fade effects in menus, are not supported by the GDI in Windows 9x.
On desktop machines, Windows Explorer
Windows Explorer
This article is about the Windows file system browser. For the similarly named web browser, see Internet ExplorerWindows Explorer is a file manager application that is included with releases of the Microsoft Windows operating system from Windows 95 onwards. It provides a graphical user interface...
is the default user interface, though a variety of additional Windows shell replacement exist.
Other GUIs include LiteStep
LiteStep
LiteStep is a Windows Shell replacement for Windows 9x and up, licensed under the terms of the GNU General Public License .LiteStep may appeal to people who like their desktop to be visually appealing, people who like to configure their environment, Unix/Linux users, and people who find the Start...
, bbLean
BbLean
bbLean is a shell replacement for Microsoft Windows. It is a development branch of BB4Win, and like that shell, it has a minimalist look. bbLean deviates slightly from the minimalist intent of its parent by offering added functionality while retaining the basic simplicity of BB4Win.Despite this...
and Program Manager
Program Manager
Program Manager is the shell of Windows 3.x and Windows NT 3.x operating systems. This shell exposed a task-oriented graphical user interface , consisting of icons arranged into program groups. It replaced MS-DOS Executive, a file manager, as the default Windows shell.The program derives from the...
. The GUI provides a means to control the placement and appearance of individual application windows, and interacts with the Window System.