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Windows "9x"

Screenshot of Windows 95, the first version of Windows in the 9x series
Company/
developer		 Microsoft
Source model Closed source
Kernel type Monolithic kernel
Default user interface Graphical user interface (command line interface also available)
License MS-EULA
Working state Unsupported

Windows 9x is the family of Microsoft Windows operating systems that comprises the 32-bit, DOS-based Windows versions: Windows 95, Windows 98, and often also Windows Me,[1] which were produced in the 1990s and 2000. The software industry comprises businesses involved in the development, maintenance and publication of Computer software. A software developer is a person or organization concerned with facets of the software development process wider than design and coding a somewhat broader scope of Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer Proprietary software is Computer software on which the producer has set restrictions on use private modification copying, or republishing. In Computer science, the kernel is the central component of most computer Operating systems (OS A monolithic kernel is a kernel architecture where the entire kernel is run in Kernel space in Supervisor mode. The user interface (or Human Computer Interface) is the aggregate of means by which people&mdash the users '&mdash interact with the System A software license (or software licence in commonwealth usage is a Legal instrument governing the usage or redistribution of copyright protected software Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination The range of Integer values that can be stored in 32 bits is 0 through 4294967295 or −2147483648 through 2147483647 using Two's complement encoding MS-DOS (short for M icro' s' oft D isk O perating S ystem is an Operating system commercialized by Microsoft. Windows 95 is a consumer-oriented Graphical user interface -based Operating system. Windows 98 ( codenamed Memphis) is a graphical Operating system released on 25 June 1998 by Microsoft and the successor to Windows 95 Windows Millennium Edition, or Windows Me (IPA pronunciation, iː is a hybrid 16-bit / 32-bit graphical Operating system released on 14 September All these Windows releases have internal version numbers in the 4. x series.

Contents

Overview

Similar to Windows 3.x, the Windows 9x operating systems require the MS-DOS kernel (IO.SYS) to boot. IOSYS is an essential part of MS-DOS and Windows 9x. It contains the default MS-DOS Device drivers (hardware interfacing routines and the DOS initialization In addition, the MS-DOS memory manager (HIMEM.SYS) is required when running in real-mode (MS-DOS mode, without the Windows GUI). HIMEM is a DOS Device driver which allows DOS programs to store data in Extended memory via the Extended Memory Specification (XMS WIN. COM is executed to launch the graphical user interface. Unlike Windows 3. x, Windows 9x's WIN. COM is loaded automatically by the system, if the "BootGUI" parameter is set to 1 in MSDOS.SYS. MSDOSSYS an important system file on MS-DOS and Windows 9x systems During this process, the CPU is switched from real mode to protected mode, and several virtual device drivers (VxDs) are loaded. Real mode, also called real address mode, is an operating mode of 80286 and later X86 -compatible CPUs. In computing protected mode, also called protected virtual address mode, is an operational mode of X86 -compatible Central processing units (CPU VxD is the Device driver model used in Microsoft Windows/386, the 386 enhanced mode of Windows 3 These VxDs allow Windows 9x to interact with hardware resources directly as well as providing several low-level functionalities such as 32-bit disk access and memory management. 32-bit Disk Access (also known as FastDisk) refers to a special disk access and caching mode available in older MS-DOS -based Microsoft Windows operating

Windows 9x consists of both 32-bit and 16-bit code. The Win32 API is entirely 32-bit and runs in protected mode, but DOS-based components, such as the MS-DOS kernel and many of its device drivers and external commands are 16-bit and runs in real or V86 mode. The Windows API, informally WinAPI, is Microsoft's core set of Application programming interfaces (APIs available in the Microsoft Windows Operating In computing a device driver or software driver is a Computer program allowing higher-level computer programs to interact with a Hardware device Additionally, some of the programs that ship with the operating system, such as ScanDisk and Disk Defragmenter, come in two versions: real mode (e. SCANDISK or ScanDisk is a utility in MS-DOS and Microsoft Windows systems which checks and repairs File systems and bad clusters on g. scandisk. exe) and protected mode (e. g. scandskw. exe).

Microsoft explains the following:[2]

"Some functions, however, are handled by MS-DOS code, although the code itself is running in virtual 8086 mode, not real mode. Functions implemented in this manner ensure backward compatibility with existing real-mode software, such as the Novell NetWare client. "

The DOS functions mentioned above are handled by the files DOSMGR. VXD and V86MMGR. VXD.

Windows 9x is designed as a single-user system. Thus, the security model is less effective than the one in Windows NT. One reason for this is the FAT file systems (including FAT12/16/32), which are the only ones that Windows 9x supports officially, although Windows NT also supports FAT and Windows 9x can be extended to read and write NTFS volumes using third-party Installable File System drivers. Templateinfobox filesystem whilst covering all 3 file systems please make any style changes to both at the same time In Computing, a file system (often also written as filesystem) is a method for storing and organizing Computer files and the data they contain to make The Installable File System ( IFS) is a Filesystem API in IBM OS/2 and Microsoft Windows NT that enables the Operating 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 lists and file-system level encryption like NTFS. In Computer security, an access control list ( ACL) is a list of permissions attached to an object The Encrypting File System (EFS is a file system driver that provides Filesystem-level encryption in Microsoft Windows ( 2000 and later operating NTFS (New Technology File System Is the standard File system of Windows NT, including its later versions Windows 2000, Windows XP, Windows [3]

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 NT is a family of Operating systems produced by Microsoft, the first version of which was released in July 1993 Windows 2000 (also referred to as Win2K) is a preemptive, interruptible graphical and business-oriented Operating system designed to work with

Architecture

The user-mode parts of Windows 9x consists of three subsystems: the Win16 subsystem, the Win32 subsystem and MS-DOS. [4] 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. The Graphics Device Interface (GDI is one of the three core components or "subsystems" together with the kernel and the Windows API for the user interface "kernel space" redirects here For mathematical definition see Null space. The kernel-mode parts consists of the Virtual Machine Manager (VMM), the Installable File System Manager (IFSHLP), the Configuration Manager, and in Windows 98 and later, also the WDM Driver Manager (NTKERN). IFSHLPSYS is an MS-DOS device driver included with Microsoft Windows. In Computing, the Windows Driver Model ( WDM) &mdash also known at one point as the Win32 Driver Model &mdash is a framework for Device drivers [5] As a 32-bit operating system, virtual memory space is 4 GiB, divided fixed, lower 2 GiB for applications and upper 2 GiB for kernel per process. A gibibyte (a contraction of gi ga bi nary byte) is a unit of Information or Computer storage, abbreviated GiB.

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 directory which stores settings and options for the Operating system for Microsoft Windows 32-bit versions 64-bit versions and 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 . AUTOEXECBAT is the name of a system file found originally on the MS-DOS operating system CONFIGSYS is the primary Configuration file for the DOS and OS/2 Operating systems It is a special file that contains setup or configuration WININI is a basic INI file that was used in versions of the Microsoft Windows Operating environment up to Windows 3 SYSTEMINI was a basic INI file used in early versions of Microsoft Windows to load Device drivers and the default Windows shell ( Program 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.

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 one of the core components of Windows 9x. The VMM creates virtual MS-DOS environments for system processes and Windows applications that still need to run in MS-DOS mode. The VMM is the replacement for Win386 in Windows 3. x, and the file vmm32. vxd is a monolithic file which contains many basic VxDs that are needed for booting Windows.

Device drivers

Device drivers in Windows 9x can be virtual device drivers or (starting with Windows 98) WDM drivers. In computing a device driver or software driver is a Computer program allowing higher-level computer programs to interact with a Hardware device VxDs usually have the filename extensions . A filename extension is a suffix to the name of a Computer file applied to indicate the encoding convention ( File format) of its contents vxd or . 386 and 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). [6]

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. Dynamic-link library (also written without the hyphen or DLL, is Microsoft 's implementation of the Shared library concept in the Microsoft Windows DLL).

File management

Like Windows for Workgroups 3.11, Windows 9x provides support for 32-bit file access, and unlike Windows 3. Windows 31x was a major release of Microsoft Windows. Several editions were released between 1992 and 1994 succeeding Windows 3 32-bit file access refers to the higher performance Protected mode disk caching method introduced in Windows for Workgroups 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 filenames. Long filenames ( LFN) spelled "long file names" by Microsoft are longer and therefore more descriptive Filenames supported by the Microsoft An 83 filename (also called a short filename or SFN) is a Filename convention used by old versions of DOS and versions of Microsoft Windows

Advantages and disadvantages

Advantages

Windows 9x is a hybrid 16/32-bit operating system. It typically has lower system requirements than contemporary Windows NT versions.

The graphical user interface (GUI) runs on a DOS-based layer. Through Windows 9x's memory managers and other post-DOS improvements, the overall system performance and functionality is improved.

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). This differs from the emulation used in Windows NT-based operating systems. Some very old applications or hardware require "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' <enter> 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. The Recovery Console is a feature of the Windows 2000, Windows XP and Windows Server 2003 operating systems Windows 2000 (also referred to as Win2K) is a preemptive, interruptible graphical and business-oriented Operating system designed to work with

Windows 9x can run some software that does not run on Windows NT. But Windows XP (which is inherently a version of Windows NT), has compatibility mode to allow Win32 applications for 9x to run seamlessly. Windows XP is a family of 32-bit and 64-bit Operating systems produced by Microsoft for use on Personal computers including home and The Windows API, informally WinAPI, is Microsoft's core set of Application programming interfaces (APIs available in the Microsoft Windows Operating

Disadvantages

Software Protection

Windows 9x has never been as stable as common users required, for many reasons. 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. Windows 9x can gain high stability, by using high quality device drivers and carefully selecting application programs.

User access

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. Multi-user is a term that defines an Operating system or Application software that allows concurrent access by multiple users of a Computer. 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. In computing a process is an instance of a Computer program that is being sequentially executed by a computer system that has the ability to run several computer 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.

Support for software and hardware

There is no native support for SATA drives, hyper-threading, Data Execution Prevention, symmetric multiprocessing or multi-core processors, and most hardware manufacturers do not ship drivers for Windows 98 SE any more, so current high-end graphics cards and peripherals may not work properly or at all. Hyper-threading (officially termed Hyper-Threading Technology or HTT) is an Intel-proprietary technology Data Execution Prevention ( DEP) is a security feature included in modern Microsoft Windows Operating systems that is intended to prevent an application In Computing, symmetric multiprocessing or SMP involves a Multiprocessor computer-architecture where two or more identical processors can connect to a single A multi-core processor (or chip-level multiprocessor, CMP) combines two or more independent cores into a single package composed of a single Integrated

Alpha compositing and therefore transparency effects, such as fade effects in menus, are not supported. In Computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial transparency Transparency is possible in a number of graphics file formats

Windows 9x does not natively support NTFS and HPFS. NTFS (New Technology File System Is the standard File system of Windows NT, including its later versions Windows 2000, Windows XP, Windows HPFS or High Performance File System is a File system created specifically for the OS/2 Operating system to improve upon the limitations Also, there is no support for event logging and tracing which the Windows NT family of operating systems has. In Software engineering, tracing is a specialized use of logging to record information about a program's execution

Design problems

Windows 9x has a number of bugs and design deficiencies that have contributed to its instability when compared with Windows NT and other operating systems.

c:\con\con

One of the most popular and most circulated bugs in Windows 95 and Windows 98 is the c:\con\con bug, which can only be achieved by using one of the File Allocation Table file systems. Concon is a Computer bug that appeared in the Windows 95 and Windows 98 Operating systems The name comes from the fact that referring to the Templateinfobox filesystem whilst covering all 3 file systems please make any style changes to both at the same time By entering "c:\con\con" (without the quotes) into the address bar of Windows Explorer, there is a conflict between Windows and the file system, causing the computer to crash. The Blue Screen of Death (also known as a stop error, BSoD, bluescreen, or Blue Screen of Doom) is an Error screen displayed Entering c:\con\con in the run dialog box also produces the same result, although Windows 95 produces a more severe error. This can also be achieved by entering "c:\nul\nul" (without quotes) into the address bar. [7]

Microsoft released a patch to remove the bug in 1999. Windows Me does not have this bug. [8]

Unprotected region of memory

Although Windows 9x features memory protection, it does not protect the first megabyte of memory from userland applications. Memory protection is a way to control memory usage on a computer and is core to virtually every Operating system. Userland refers to an application space that is external to the kernel and is protected by Privilege separation. 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. A crash in Computing is a condition where a program (either an application or part of the Operating system) stops performing its expected function and also This article is about the computer malfunction called hanging. This was a source of instability as faulty applications could by accident write into this region and with that halt the operating system. [9]

Drivers share address space with the kernel

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. Windows NT too is susceptible to this issue, however, with the introduction of User-Mode Driver Framework for Windows XP and later operating systems, this issue is addressed. The User-Mode Driver Framework is a device-driver development platform first introduced with Microsoft 's Windows Vista Operating system, and is also available

Timeout code depends on the execution speed

Windows 95 can fail to boot on systems faster than 350 MHz. The reason is due to a timeout loop that depends on the execution speed of the processor. The timeout loop is used for dealing with hardware devices incapable of keeping up with the full speed of the system, such as hard drives. If a processor executes the loop too fast the slow device can fail to function properly and possibly prevent the operating system from booting.

A patch for this issue can be downloaded from Microsoft, but users must be able to boot the OS to install it. [10]

Disk corruption on shutdown

When Windows 95/98/Me shut down, they use a timeout loop to give hard drives time to commit their write back caches to their platters. On fast CPUs or with disks fitted with large write back caches this timeout can run out before the disk has committed its write back cache, which can lead to disk corruption and loss of data.

A patch for this issue can be downloaded from Microsoft. [11]

Out of memory with large amount of RAM installed

The Windows 9x/Me VCache is limited to a size of 800 MB. This 800 MB includes system and video memory, and on systems where the combined video and system memory exceeds 800 megabytes the operating system may fail to boot with a 'out of memory' error.

There is a workaround for this issue. [12]

Limited system resources

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, one could exhaust these memory areas. If free system resources dropped below 10%, Windows would become unstable and likely crash. [13]

Crash after 49. 7 days of uptime

Due to a timing error, Windows may crash after continuously running for about a month and a half. This affected unpatched versions of Windows 95 and Windows 98. [14]

Altering critical files

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. In Computing, DLL hell is a colloquial term for the complications that arise when working with dynamic link libraries, (DLLs used with Microsoft Windows

Windows Me introduced System File Protection and System Restore to handle common problems caused by this issue. Windows File Protection (WFP is a technology included in all Microsoft Windows Operating systems beginning with Windows 2000 to prevent programs from replacing System Restore is a component of Microsoft 's Windows Me, Windows XP and Windows Vista Operating systems that allows for the rolling

Releases

The following Windows 9x/Me versions were released:[15]

Plus! packs

Criticism

Windows 9x is often characterized as being unstable—it is widely panned for its instability, displaying the "Blue Screen of Death", when abruptly terminating an application—usually due to the way drivers had to be written in order to accommodate the Windows kernel structure. Microsoft Plus! is a commercial Operating system enhancement product by Microsoft. The Blue Screen of Death (also known as a stop error, BSoD, bluescreen, or Blue Screen of Doom) is an Error screen displayed

References

  1. ^ In common usage, the term "Windows 9x" itself may or may not include Windows Me. Another term "Windows 9x/Me" is often used to explicitly include Windows Me. In the main part of this article they will be treated as synonyms.
  2. ^ Windows 95 performance tuning: The basics
  3. ^ FAT32 or NTFS: Making the choice - Theeldergeek.com
  4. ^ Windows 95 architecture components
  5. ^ Windows 98 architecture
  6. ^ Function of the Windows 32-Bit message server - Microsoft Help and Support
  7. ^ Bugtraq: con\con is a old thing (anyway is cool)
  8. ^ Fatal exception 0E with multiple MS-DOS device names in path
  9. ^ Windows XP Chat Transcript
  10. ^ Difficulties using AMD K6-2 or Athlon CPU
  11. ^ ScanDisk runs even though Windows shut down correctly
  12. ^ Error messages with large amounts of RAM Installed"
  13. ^ Resource management under Microsoft Windows
  14. ^ "CNET - Windows may crash after 49.7 days"
  15. ^ How to determine the version of Windows 95/98/Me in use
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