Windows 9x

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**Windows "9x"**
Screenshot of Windows 95, the first Windows in the 9x series
Company/ developer:	Microsoft
Source model:	Closed source
Kernel type:	Hybrid kernel
Default user interface:	Graphical User Interface
License:	MS-EULA
Working state:	Unsupported

Windows 9x is a term used to describe the DOS-based operating systems Windows 95 and Windows 98, similar versions of Microsoft Windows which were produced in the 1990s. Occasionally, Windows Me is also included in the term, as it is very similar in many respects.

1 Overview
2 Releases
- 2.1 Plus! packs
3 References

[edit] Overview

Unlike Windows 3.x, the Windows 9x operating systems are not running on top of MS-DOS. When the graphical user interface is launched, Windows switches from real mode to protected mode. For example, the memory mangement in Windows is different from the one in MS-DOS. However, MS-DOS is still important because Windows 9x will not start without using the MS-DOS boot component (IO.SYS).

Windows 95, 98, and Me consist of both 32-bit and 16-bit code. The Win32 API is entirely 32-bit, but DOS-based components, such as the boot loader and many of its device drivers are 16-bit. Additionally, some of the programs that ship with the operating system are also 16-bit.

Windows 95, 98, and Me are designed to be a single-user system and the security model is therefore not comparable to the one in Windows NT. One reason of that is the FAT and FAT32 which are the only file systems that Windows 9x officially supports, although Windows NT also supports FAT. FAT and FAT32 have very limited security; every user that has access to a FAT drive also has access to all files on that drive. The file systems provide no access control lists like NTFS^[1].

[edit] Device drivers

Device drivers in Windows 9x can be virtual device drivers or WDM drivers. VxDs usually have the filename extensions .vxd or .386 and WDM compatible drivers usually use the extension .sys. The 32-bit VxD message server (msgsrv32) is the program that loads virtual device drivers (VxDs) at startup and then handles communication with the drivers. Additionally, the message server performs several background functions, including loading the Windows shell (such as Explorer.exe or Progman.exe)^[2].

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.

[edit] Virtual Machine Manager

The Virtual Machine Manager (VMM) is one of the core components of Windows 9x. VMM create virtual machine environments for system processes and Windows applications. VMM is the replacement for Win386 in Windows 3.x.

[edit] File management

Like Windows for Workgroups 3.11, Windows 9x provide support for 32-bit file access, and unlike Windows 3.x, Windows 9x has support for the VFAT file system, allowing file names with a maximum of 255 character instead of having 8.3 file naming.