MSDOS.SYS is a system file in

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 o ...

and

Windows 9x Windows 9x is a generic term referring to a series of Microsoft Windows computer operating systems produced from 1995 to 2000, which were based on the Windows 95 kernel and its underlying foundation of MS-DOS, both of which were updated in sub ...

operating systems. In versions of MS-DOS from 1.1x through 6.22, the file comprises the MS-DOS

kernel Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learn ...

and is responsible for file access and program management. MSDOS.SYS is loaded by the

DOS BIOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

IO.SYS 




 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 program.
  Boot sequence 
In the  PC bootup sequence, the first sector of the boot disk is ...

as part of the

boot A boot is a type of footwear. Most boots mainly cover the foot and the ankle, while some also cover some part of the lower calf. Some boots extend up the leg, sometimes as far as the knee or even the hip. Most boots have a heel that is c ...

procedure. In some OEM versions of MS-DOS, the file is named MSDOS.COM. In

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturi ...

(MS-DOS 7.0) through

Windows ME Windows Millennium Edition, or Windows Me (marketed with the pronunciation of the pronoun "me"), is an operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It is the successor to Windo ...

(MS-DOS 8.0), the DOS kernel has been combined with the DOS BIOS into a single file, IO.SYS (aka WINBOOT.SYS), while MSDOS.SYS became a

plain text In computing, plain text is a loose term for data (e.g. file contents) that represent only characters of readable material but not its graphical representation nor other objects (floating-point numbers, images, etc.). It may also include a limit ...

file containing boot configuration directives instead. If a WINBOOT.INI file exists, the system will retrieve these configuration directives from WINBOOT.INI rather than from MSDOS.SYS. When Windows 9x is installed over a preexisting DOS install, the Windows file may be temporarily named MSDOS.W40 for as long as Windows' dual-boot feature has booted the previous OS. Likewise, the MSDOS.SYS of the older system is named MSDOS.DOS for as long as Windows 9x is active. Some DOS utilities expect the MSDOS.SYS file to have a minimal file size of at least 1 KB. This is the reason why a large dummy comment is typically found in the MSDOS.SYS configuration file since Windows 95. By default, the file is located in the

root directory In a computer file system, and primarily used in the Unix and Unix-like operating systems, the root directory is the first or top-most directory in a hierarchy. It can be likened to the trunk of a tree, as the starting point where all branche ...

of the bootable drive/partition (normally C:\ for hard disks) and has the hidden, read-only, and system file attributes set. The MS-DOS derivative (DCP) by the former East-German

VEB Robotron VEB Kombinat Robotron (or simply Robotron) was the biggest East German electronics manufacturer. It was based in Dresden and employed 68,000 people (1989). It produced personal computers, SM EVM minicomputers, the ESER mainframe computers, se ...

used a filename instead.

IBM PC DOS IBM PC DOS, an acronym for IBM Personal Computer Disk Operating System, is a discontinued disk operating system for IBM PC compatibles. It was manufactured and sold by IBM from the early 1980s into the 2000s. Developed by Microsoft, it was also ...

as well as DR DOS since 5.0 (with the exception of DR-DOS 7.06) used the file

IBMDOS.COM 


 
IBMDOS.COM is the filename of the DOS kernel. Loaded and initially invoked by the  DOS BIOS in  IBMBIO.COM during the boot process, it contains the hardware-independent parts of the operating system, including the embedded FAT12, FAT16 and ...

for the same purpose, whereas DR DOS 3.31 to 3.41 used DRBDOS.SYS instead.

FreeDOS FreeDOS (formerly Free-DOS and PD-DOS) is a free software operating system for IBM PC compatible computers. It intends to provide a complete MS-DOS-compatible environment for running legacy software and supporting embedded systems. FreeDOS can ...

uses the file KERNEL.SYS for the same purpose.

Windows NT Windows NT is a proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993. It is a processor-independent, multiprocessing and multi-user operating system. The first version of Win ...

-based operating systems (NT 3.1–4, 2000, XP, and 2003) use the NTLDR file and NT 6+ operating systems (Vista, 2008, 7, 8, 8.1, and 10) use

bootmgr The booting process of Windows Vista and later versions differ from the startup process part of previous versions of Windows. In this article, unless otherwise specified, what is said about Windows Vista also applies to all later NT operatin ...

instead, as they have a different boot sequence.

Notes

References

External links

MSDOS.SYS in Windows 9x (95/98/ME): * Microsoft Knowledge Base (MSKB)
List of MSDOS.SYS articles
* MDGx

* UKT Support

* Computer Hope

* MDGx

{{DOS system files DOS kernel DOS files DOS configuration files

See also

Notes

References

External links