Windows 9x
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Windows 9x is a generic term referring to a line of discontinued
Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...
s released from 1995 to 2000 and supported until 2006, which were based on the kernel introduced in
Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...
and modified in succeeding versions, with its underlying foundation based on
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...
. The first version in the 9x series was Windows 95, which was succeeded by
Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the second operating system in the 9x line, as the successor to Windows 95. It was Software ...
and then
Windows Me Windows Me (Millennium Edition) is an operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the successor to Windows 98, and was released to manufacturing on June 19, 2000, and t ...
, which was the third and last version of Windows on the 9x line, until the series was superseded by
Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...
. Windows 9x is predominantly known for its use in home desktops. In 1998, Windows made up 82% of operating system market share. The internal release number for versions of Windows 9x is 4.x. The internal versions for Windows 95, 98, and Me are 4.0, 4.1, and 4.9, respectively. Previous MS-DOS-based versions of Windows used version numbers of 3.2 or lower.
Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...
, which was aimed at professional users such as networks and businesses, used a similar but separate version number between 3.1 and 4.0. All versions of Windows from
Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...
onwards are based on the Windows NT codebase.


History


Windows prior to 95

The first independent version of Microsoft Windows, version 1.0, released on November 20, 1985, achieved little popularity. Its name was initially "Interface Manager", but
Rowland Hanson Rowland Hanson, (born 1952) is the current Chairman of CRH & Associates, and the CEO of the HMC Company. He is known for his work in Microsoft, where he convinced the company to name their new graphical user interface (GUI) "Windows" over the origi ...
, 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 ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...
. Consequently, it shared the inherent flaws and problems of MS-DOS. The second installment of Microsoft Windows, version 2.0, was released on December 9, 1987, and used the
real-mode Real mode, also called real address mode, is an operating mode of all x86-compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20- bit ...
memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembe ...
model, which confined it to a maximum of 1
megabyte The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes ...
of memory. In such a configuration, it could run under another multitasking system like
DESQview DESQview (DV) is a text mode multitasking operating environment developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s. Running on top of DOS, it allows users to run multiple programs concurr ...
, which used the 286
Protected Mode In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as Memory_segmentation, segmentation, virtual mem ...
. 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 In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a ver ...
. Microsoft developed Windows 3.1, which included several improvements to Windows 3.0. It also excluded support for Real mode, and only ran on an
Intel 80286 The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non- multiplexed address and data buses and also the f ...
or better processor. Windows 3.1 was released on April 6, 1992. In November 1993 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 early 1992. Meanwhile, Microsoft continued to develop
Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...
. The main architect of the system was Dave Cutler, one of the chief architects of VMS at
Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until ...
. Microsoft hired him in August 1988 to create a successor to
OS/2 OS/2 is a Proprietary software, proprietary computer operating system for x86 and PowerPC based personal computers. It was created and initially developed jointly by IBM and Microsoft, under the leadership of IBM software designer Ed Iacobucci, ...
, but Cutler created a completely new system instead based on his
MICA Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...
project at Digital. The first version of Windows NT, Windows NT 3.1, would be released on July 27, 1993 and used Windows 3.1's interface. About a year before the development of Windows 3.1's successor (Windows 95, code-named Chicago) began, Microsoft announced at its 1991
Professional Developers Conference Microsoft's Professional Developers Conference (PDC) was a series of conferences for software developers; the conference was held infrequently to coincide with beta releases of the Microsoft Windows, Windows operating system, and showcased topic ...
that they would be developing a successor to Windows NT code-named
Cairo Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...
, which was viewed by some as the successor to Windows NT and Windows 3.1's successor, under the implication that the two operating systems would be combined into one unified system. Microsoft publicly demonstrated Cairo at the 1993 Professional Developers Conference, complete with a demo system running Cairo for all attendees to use. Based on the
Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...
kernel, Cairo was a next-generation operating system that was to feature as many new technologies into Windows, including a new user interface with an object-based file system (the new user interface would officially debut with Windows 95 nearly 4 years later while the object-based file system would later be adopted as WinFS during the
development of Windows Vista Development or developing may refer to: Arts *Development (music), the process by which thematic material is reshaped *Photographic development *Filmmaking#Development, Filmmaking, development phase, including finance and budgeting *Developm ...
). According to Microsoft's product plan at the time, Cairo was planned to be released as late as July 1996 following its development. However, it had become apparent that Cairo was a much more difficult project than Microsoft had anticipated, and the project was subsequently cancelled 5 years into development. A subset of features from Cairo were eventually added into Windows NT 4.0 released on August 24, 1996, albeit without the object file system. Windows NT and Windows 9x would not be truly unified until
Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...
nearly 5 years later, when Microsoft began to merge its consumer and business line of Windows under a singular brand name based on Windows NT.


Windows 95

After Windows 3.11,
Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
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, that of which was available in OS/2 and Windows NT, although a 16-bit kernel would remain for the sake of backward compatibility. The Win32
API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...
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 (and indeed after Cairo was cancelled 5 years in development). 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, also called real address mode, is an operating mode of all x86-compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20- bit s ...
) 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 immediately began to impact the operating system's efficiency and stability. Microsoft marketing adopted
Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...
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 (RTM) * Windows 95 A – included Windows 95 OSR1 slipstreamed into the installation. * Windows 95 B – (OSR2) included several major enhancements,
Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated as IE or MSIE) is a deprecation, retired series of graphical user interface, graphical web browsers developed by Microsoft that were u ...
(IE) 3.0 and full
FAT32 File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on ...
file system support. * Windows 95 B USB – (OSR2.1) included basic
USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...
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 ("OSR" being an initialism for "OEM Service Release") 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.


Windows 98

On June 25, 1998, Microsoft released Windows 98, code-named "Memphis" during development. It included new hardware drivers and better support for the
FAT32 File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on ...
file system which allows support for disk partitions larger than the 2 GB maximum accepted by Windows 95. The
USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...
support in Windows 98 was more robust than the basic support provided by the OEM editions of Windows 95. It also introduces the controversial integration of the
Internet Explorer 4 Microsoft Internet Explorer 4 (IE4) is the fourth version of the Internet Explorer graphical web browser that Microsoft unveiled in Spring of 1997, and released on September 22, 1997, primarily for Microsoft Windows, but also with versions availa ...
web browser into the
Windows shell The Windows shell is the graphical user interface for the Microsoft Windows operating system. Its readily identifiable elements consist of the desktop, the taskbar, the Start menu, the task switcher and the AutoPlay feature. On some versions of ...
and
File Explorer File Explorer, previously known as Windows Explorer, is a file manager application and default desktop environment that is included with releases of the Microsoft Windows operating system from Windows 95 onwards. It provides a graphical user i ...
(then known as Windows Explorer at the time). On June 10, 1999, Microsoft released Windows 98 Second Edition (also known as Windows 98 SE), an interim release whose notable 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 Network address translation (NAT) is a method of mapping an IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic Router (computing), routing device. The te ...
, allowing several machines on a LAN (Local Area Network) to share a single Internet connection. It also includes Internet Explorer 5 as opposed to Internet Explorer 4 in the original version. Windows 98 Second Edition also has certain improvements over the original release, and hardware support through device drivers was increased. Many minor problems present in the original release of Windows 98 were also found and fixed. These changes, among others, makes it (according to many) the most stable release of Windows 9x family—to the extent that some commentators used to say that Windows 98's
beta version The software release life cycle is the process of developing, testing, and distributing a software product (e.g., an operating system). It typically consists of several stages, such as pre-alpha, alpha, beta, and release candidate, before the fi ...
was more stable than Windows 95's final (gamma) version. Like with Windows 95, Windows 98 received the Microsoft Plus! add-on in the form of Plus! 98.


Windows Me

On September 14, 2000, Microsoft introduced Windows Me (Millennium Edition; also known as Windows ME), which upgraded Windows 98 with enhanced multimedia and Internet features. Code-named "Millennium", It was conceived as a quick one-year project that served as a stopgap release between Windows 98 and Windows XP (then code-named Whistler at the time). It borrowed some features from the business-oriented
Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft, targeting the server and business markets. It is the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RT ...
into the Windows 9x series, and introduced the first version of
System Restore System Restore is a feature in Microsoft Windows that allows the user to revert their computer's state (including system files, installed applications, Windows Registry, and system settings) to that of a previous point in time, which can be used ...
, which allowed users to revert their system state to a previous "known-good" point in the case of a system failure. Windows Me also introduced the first release of
Windows Movie Maker Windows Movie Maker (known as Windows Live Movie Maker for the 2009 and 2011 releases) is a discontinued video editing software program by Microsoft. It was first included in Windows Me on September 14, 2000, and in Windows XP on October 25, 200 ...
and included Windows Media Player 7. Internet Explorer 5.5 came shipped with Windows Me. Many of the new features from Windows Me were also available as updates for older Windows versions such as Windows 98 via
Windows Update Windows Update is a Microsoft service for the Windows 9x and Windows NT families of the Microsoft Windows operating system, which automates downloading and installing Microsoft Windows software updates over the Internet. The service delivers sof ...
. The role of MS-DOS has also been greatly reduced compared to previous versions of Windows, with Windows Me no longer allowing real mode DOS to be accessed. Windows Me initially gained a positive reception upon its release, but later on it was heavily criticized by users for its instability and unreliability, due to frequent freezes and crashes. Windows Me has been viewed by many as one of the worst operating systems of all time, both in critical and in retrospect. ''PC World'' was highly critical of Windows Me months after it was released (and indeed when it was no longer available), with their article infamously describing Windows Me as "Mistake Edition" and placing it 4th in their "Worst Tech Products of All Time" feature in 2006. Consequently, many home users that were affected by Windows Me's instabilities (as well as those who negatively viewed Windows Me) ultimately stuck with the more reliable Windows 98 Second Edition for the remainder of Windows Me's lifecycle until the release of Windows XP in 2001. A small number of Windows Me owners moved over to the business-oriented Windows 2000 Professional during that same time period. The inability of users to easily boot into real mode MS-DOS like in Windows 95 and 98 led users to quickly figure out how to hack their Windows Me installations to provide this missing functionality back into the operating system. Unlike Windows 95 and Windows 98, Windows Me did not receive a dedicated Microsoft Plus! add-on pack for it.


Decline

The release of
Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft, targeting the server and business markets. It is the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RT ...
marked a shift in the user experience between the Windows 9x series and the Windows NT series. Windows NT 4.0, while based on the Windows 95 interface, suffered from a lack of support for USB,
Plug and Play In computing, a plug and play (PnP) device or computer bus is one with a specification that facilitates the recognition of a hardware component in a system without the need for physical device configuration or user intervention in resolving reso ...
and
DirectX Microsoft DirectX is a collection of application programming interfaces (APIs) for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with "Direct" ...
versions after 3.0, preventing its users from playing contemporary games. Windows 2000 on the other hand, while primarily made towards business and server users, featured an updated user interface and better support for both Plug and Play and USB, as well as including built-in support for DirectX 7.0. The release of
Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...
in late 2001 confirmed the change of direction for Microsoft, bringing the consumer and business operating systems together under Windows NT. It also introduced a "compatibility mode" option, which allowed certain software to run as they would on earlier versions of Windows depending on the Windows version being used. After the release of Windows XP, Microsoft stopped selling Windows 9x releases to end users (and later to OEMs) in the early 2000s. By March 2004, it was impossible to purchase any versions of the Windows 9x series.


End of support

Over time, support for the Windows 9x series ended. Windows 95 lost its mainstream support on December 31, 2000, and extended support was dropped from Windows 95 on December 31, 2001 (which also ended support for older Windows versions prior to Windows 95 on that same day). Windows 98 and Windows 98 Second Edition had its mainstream support end on June 30, 2002, and mainstream support for Windows Me ended on December 31, 2003. Microsoft then continued to support the Windows 9x series until July 11, 2006, when extended support ended for Windows 98, Windows 98 Second Edition (SE), and Windows Millennium Edition (Me) – 4 years after extended support for Windows 95 ended on December 31, 2001. Microsoft DirectX, a set of standard gaming APIs, stopped being updated on Windows 95 at version 8.0a. It also stopped being updated on Windows 98 and Me after the release of
Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...
in 2006, making DirectX 9.0c the last version of DirectX to support these operating systems. Support for
Microsoft Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated as IE or MSIE) is a retired series of graphical web browsers developed by Microsoft that were used in the Windows line of operating ...
on all Windows 9x releases have also ended. Windows 95, Windows 98 and Windows Me all lost security patches for Internet Explorer when the respective operating systems reached their end of support date. Internet Explorer 5.5 with Service Pack 2 is the last version of Internet Explorer compatible with Windows 95, while Internet Explorer 6 with Service Pack 1 is the last version compatible with latter releases of Windows 9x (i.e. 98 and Me). While Internet Explorer 6 for Windows XP did receive security patches up until it lost support, this is not the case for IE6 under Windows 98 and Me. Due to its age,
Internet Explorer 7 Windows Internet Explorer 7 (IE7) (codenamed Rincon) is a version of Internet Explorer, a web browser for Windows. It was released by Microsoft on October 18, 2006. It was the first major update to the browser since 2001. It does not support ve ...
, the first major update to Internet Explorer 6 in half a decade, was only available for Windows XP SP2 and Windows Vista. In 2011, Microsoft retired the Windows Update v4 website and removed the updates for Windows 98, Windows 98 SE, and Windows Me from its servers. Despite this, an independent project named Windows Update Restored was created in 2022 that aims to restore the Windows Update websites for older versions of Windows, including all releases of Windows 9x. Microsoft announced in July 2019 that the Microsoft Internet Games services on Windows Me (and XP) would end on July 31, 2019 (and for Windows 7 on January 22, 2020).


Current usage

The growing number of important updates caused by the end of life service for these operating systems have slowly made Windows 9x even less practical for everyday use. Today, even open source projects such as
Mozilla Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements curren ...
will not run on Windows 9x without major rework. RetroZilla is a fork of
Mozilla Application Suite The Mozilla Application Suite (originally known as Mozilla, marketed as the Mozilla Suite) is a discontinued cross-platform integrated Internet suite. Its development was initiated by Netscape Communications Corporation, before their acquisition ...
1.1.xx (running on Gecko 1.8.1) aimed at bringing "improved compatibility on the modern web" for versions of Windows as old as Windows 95 and NT 4.0. The latest version, 2.2, was released in February 2019 and added support for TLS 1.2.


Design


Kernel

Windows 9x is a series of monolithic 16/32-bit operating systems. Like most operating systems, Windows 9x consists of
kernel space A modern computer operating system usually uses virtual memory to provide separate address spaces or regions of a single address space, called user space and kernel space. This separation primarily provides memory protection and hardware prote ...
and
user space A modern computer operating system usually uses virtual memory to provide separate address spaces or regions of a single address space, called user space and kernel space. This separation primarily provides memory protection and hardware prote ...
memory. Although Windows 9x features some
memory protection Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that h ...
, it does not protect the first megabyte of memory from userland applications for compatibility reasons. 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 accidentally write into this region, potentially corrupting important operating system memory, which usually resulted in some form of system error and halt.


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 KiB memory regions for
GDI GDI may refer to: Science and technology * Gasoline direct injection, a type of fuel injection * Graphics Device Interface, a component of Microsoft Windows * Guanosine nucleotide dissociation inhibitor, a protein Organisations * Gabriel Dumont I ...
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 ( IFSHLP), 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.


Registry

Like Windows NT, Windows 9x stores user-specific and configuration-specific settings in a large information database called the
Windows registry The Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the registry. The kernel, device drivers, services, Security Accounts Manager, a ...
. 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.


Virtual Machine Manager

The Virtual Machine Manager (VMM) is the
32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in a maximum of 32- bit units. Compared to smaller bit widths, 32-bit computers can perform la ...
protected mode In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as Memory_segmentation, segmentation, virtual mem ...
kernel at the core of Windows 9x. Its primary responsibility is to create, run, monitor and terminate
virtual machine In computing, a virtual machine (VM) is the virtualization or emulator, emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve ...
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 A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions ...
) 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 vmm.386 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).


Software support


Unicode

Windows 9x has no native support for
Unicode Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...
encoding and only officially supports
ANSI The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...
encoding, however partial Unicode encoding support be installed on Windows 9x via the Microsoft Layer for Unicode.


File systems

Windows 9x does not natively support
NTFS NT File System (NTFS) (commonly called ''New Technology File System'') is a proprietary journaling file system developed by Microsoft in the 1990s. It was developed to overcome scalability, security and other limitations with File Allocation Tabl ...
or HPFS; however, there are third-party solutions available for Windows 9x that allows read-only access to NTFS volumes. Early versions of Windows 95 did not support
FAT32 File Allocation Table (FAT) is a file system developed for personal computers and was the default file system for the MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on ...
. Like Windows for Workgroups 3.11, Windows 9x provides support for 32-bit file access based on
IFSHLP.SYS The Installable File System (IFS) is a filesystem API in MS-DOS/PC DOS 4.x, IBM OS/2 and Microsoft Windows that enables the operating system to recognize and load software driver, drivers for file systems. History When IBM and Microsoft were co- ...
. 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.


Event logging and tracing

Windows 9x has no support for event logging and tracing or error reporting that 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
FAT In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers specif ...
file systems (including FAT12/FAT16/FAT32), which are the only ones that Windows 9x supports officially, though Windows NT also supports FAT12 and FAT16 (but not FAT32; which wouldn’t be supported until Windows 2000) and Windows 9x can be extended to read and write NTFS volumes using third-party
Installable File System The Installable File System (IFS) is a filesystem API in MS-DOS/ PC DOS 4.x, IBM OS/2 and Microsoft Windows that enables the operating system to recognize and load drivers for file systems. History When IBM and Microsoft were co-developing OS/ ...
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 In computer security, an access-control list (ACL) is a list of permissions associated with a system resource (object or facility). An ACL specifies which users or system processes are granted access to resources, as well as what operations are ...
s and file-system level encryption like
NTFS NT File System (NTFS) (commonly called ''New Technology File System'') is a proprietary journaling file system developed by Microsoft in the 1990s. It was developed to overcome scalability, security and other limitations with File Allocation Tabl ...
. Some operating systems that were available at the same time as Windows 9x are either
multi-user Multi-user software is computer software that allows 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 leavi ...
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. This phenomenon is not exclusive to Windows 9x; many other operating systems are also susceptible to these vulnerabilities, either by viruses, malware or by the user’s consent. 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 System Restore is a feature in Microsoft Windows that allows the user to revert their computer's state (including system files, installed applications, Windows Registry, and system settings) to that of a previous point in time, which can be used ...
to handle common problems caused by this issue.


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.


Hardware support


Drivers

Device driver In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabli ...
s in Windows 9x can be virtual device drivers or (starting with Windows 98) WDM drivers. VxDs usually have the
filename extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (for example, .txt, .mp3, .exe) that indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...
.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
New Executable The New Executable (NE or NewEXE) is a 16-bit executable file format, a successor to the DOS MZ executable format. It was used in Windows 1.0–3.x, Windows 9x, multitasking MS-DOS 4.0, OS/2 1.x, and the OS/2 subset of Windows NT up to versio ...
format and 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 A dynamic-link library (DLL) is a shared library in the Microsoft Windows or OS/2 operating system. A DLL can contain executable code (functions), data, and resources. A DLL file often has file extension .dll even though this is not require ...
is required (such as MMSYSTEM.DLL). Windows 9x retains backwards compatibility with many drivers made for Windows 3.x and MS-DOS. Using MS-DOS drivers can limit performance and stability due to their use of conventional memory and need to run in real mode which requires the CPU to switch in and out of protected mode. Drivers written for Windows 9x 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 A hybrid kernel is an operating system Kernel (operating system), kernel whose architecture attempts to combine aspects and benefits of microkernel and monolithic kernel architectures used in operating systems. Overview The traditional kernel cat ...
s, like
Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
and
Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...
, 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 and bus technologies

Windows 9x has no native support for hyper-threading, Data Execution Prevention,
symmetric multiprocessing Symmetric multiprocessing or shared-memory multiprocessing (SMP) involves a multiprocessor computer hardware and software architecture where two or more identical processors are connected to a single, shared main memory, have full access to all ...
, APIC, or
multi-core A multi-core processor (MCP) is a microprocessor on a single integrated circuit (IC) with two or more separate central processing units (CPUs), called ''cores'' to emphasize their multiplicity (for example, ''dual-core'' or ''quad-core''). Ea ...
processors. Windows 9x has no native support for
SATA SATA (Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard ...
host bus adapters (and neither do Windows 2000 nor Windows XP for that matter), or
USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...
drives (except for Windows Me). There are, however, many SATA-I controllers for which Windows 98/Me drivers exist (and indeed Windows 2000 and Windows XP also provided SATA support via third-party drivers as well), and USB mass storage support has been added to Windows 95 OSR2 and Windows 98 through third party drivers. Hardware driver support for Windows 98/Me began to decline in 2005, most notably with motherboard
chipset In a computer system, a chipset is a set of electronic components on one or more integrated circuits that manages the data flow between the processor, memory and peripherals. The chipset is usually found on the motherboard of computers. Chips ...
s and
video card A graphics card (also called a video card, display card, graphics accelerator, graphics adapter, VGA card/VGA, video adapter, display adapter, or colloquially GPU) is a computer expansion card that generates a feed of graphics output to a displa ...
s. Early versions of Windows 95 had no support for
USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...
or AGP acceleration (including lack of
Infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
support for Windows 95 RTM). Windows 95 had preliminary support for ATAPI CD-ROMs, albeit with buggy ATAPI implementation. Windows 95 prior to OSR2 also had buggy support for processors implementing MMX as well as processors based on the P6 microarchitecture.


MS-DOS

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...
was able to reduce the role of
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...
in Windows much further than had been done in Windows 3.1x and earlier. According to Microsoft developer Raymond Chen, 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 is the expanded memory manager of Microsoft's MS-DOS, IBM's PC DOS, Digital Research's DR-DOS, and Datalight's ROM-DOS which is used to create expanded memory using extended memory on Intel 80386 CPUs. There also is an EMM386.EXE avail ...
and switch into protected mode. Once in protected mode, the virtual device drivers ( VxDs) 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 Windows Me (Millennium Edition) is an operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the successor to Windows 98, and was released to manufacturing on June 19, 2000, and t ...
, 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 Raymond Tsong-he Chen (born 1968) is an American lawyer who has served as a United States circuit judge of the United States Court of Appeals for the Federal Circuit since 2013. Early life and education Chen was born in 1968 in New York City ...
, "''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 backwards compatibility for DOS applications in the form of being able to boot into a native "DOS Mode" (MS-DOS can be booted without booting Windows, but 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. Some old applications or games may not run properly in the virtual DOS environment 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 real mode DOS. Windows 95 and Windows 98 can also be started from DOS Mode by typing 'WIN' at the command prompt and then hitting "Enter", similar to earlier versions of Windows such as Windows 3.1.


User interface

Users can control a Windows 9x-based system through a
command-line interface A command-line interface (CLI) is a means of interacting with software via command (computing), commands each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user ...
(or CLI) or a
graphical user interface A graphical user interface, or GUI, is a form of user interface that allows user (computing), users to human–computer interaction, interact with electronic devices through Graphics, graphical icon (computing), icons and visual indicators such ...
(or GUI). The default mode for Windows is usually the graphical user interface, whereas the CLI is available through
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...
windows. The GUI provides a means to control the placement and appearance of individual application windows, and interacts with the window system. The
GDI GDI may refer to: Science and technology * Gasoline direct injection, a type of fuel injection * Graphics Device Interface, a component of Microsoft Windows * Guanosine nucleotide dissociation inhibitor, a protein Organisations * Gabriel Dumont I ...
, which is a part of the Win32 and Win16 subsystems, is also a module that is loaded in
user mode A modern computer operating system usually uses virtual memory to provide separate address spaces or regions of a single address space, called user space and kernel space. This separation primarily provides memory protection and hardware prote ...
, unlike Windows NT where the GDI is loaded in kernel mode.
Alpha compositing In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate pass ...
and therefore transparency effects, such as fade effects in menus, are not supported by the
GDI GDI may refer to: Science and technology * Gasoline direct injection, a type of fuel injection * Graphics Device Interface, a component of Microsoft Windows * Guanosine nucleotide dissociation inhibitor, a protein Organisations * Gabriel Dumont I ...
in Windows 9x, unlike with Windows NT releases since Windows 2000. The default user interface of the GUI is Windows Explorer; however, a variety of additional Windows shell replacements exist. Other GUIs include LiteStep, bbLean and
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 (GUI), consisting of ''icons'' ( shortcuts for programs) arranged into ''program groups''. It replaced ...
.


In popular culture

The sheer popularity of the Windows 9x series led to several web-based projects being created in the 2010s that aimed to replicate the look and feel of Windows 9x (and indeed an actual operating system as a whole) on a single web browser while also invoking
nostalgia Nostalgia is a sentimentality for the past, typically for a period or place with happy personal associations. The word ''nostalgia'' is a neoclassical compound derived from Greek language, Greek, consisting of (''nóstos''), a Homeric word me ...
. Many of these projects (including the ones listed below) are also featured on several websites focusing on older versions of Windows and vintage computing. Developed in 2014, Windows 93 (stylized as "WINDOWS93" in the title bar) is a web-based parody site created by two French musicians and programmers who go by the names of jankenpopp and Zombectro. Being a parody of the Windows 9x series, it is purposefully designed to look and feel like an actual operating system. It features several
web applications A web application (or web app) is application software that is created with web technologies and runs via a web browser. Web applications emerged during the late 1990s and allowed for the server to dynamically build a response to the request, ...
which reference and features various internet memes from the late 1990s up to the early 2000s. In 2019, EmuOS was created, which is a web-based site designed to play retro games and applications within a web browser. It was created by Emupedia, a video game preservation and computer history community-based site. The site itself replicates the look and feel of Windows 9x as a whole to emulate an actual Windows operating system, featuring 3 themes based on all major Windows 9x releases starting from Windows 95 up to Windows Me. It also features the aforementioned Windows 93 parody site. Windows 98 has been recreated in web-based format under the name 98.js (also known as Windows 98 Online). It featured web-based versions of several classic Windows applications.


See also

* Comparison of operating systems * Architecture of Windows 9x * MS-DOS 7


References


External links

* * * {{Operating system Computing platforms 9x Discontinued versions of Microsoft Windows