is an essential part 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 ope ...

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 subs ...

. It contains the default MS-DOS

device driver In computing, 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, enabling operating systems and ot ...

s (hardware interfacing routines) and the DOS initialization program.

Boot sequence

In the PC bootup sequence, the first sector of the boot disk is loaded into memory and executed. If this is the DOS boot sector, it loads the first three sectors of into memory and transfers control to it. then: # Loads the rest of itself into memory. # Initializes each default

in turn (

console Console may refer to: Computing and video games * System console, a physical device to operate a computer ** Virtual console, a user interface for multiple computer consoles on one device ** Command-line interface, a method of interacting with ...

, disk,

serial port In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. ...

, etc..). At this point, the default devices are available. # Loads the DOS kernel and calls its initialization routine. The kernel is stored in with MS-DOS and in with Windows 9x. At this point, "normal" file access is available. # Processes the file with Windows 9x. # Processes the file, in MS-DOS 2.0 and higher and Windows 9x. # Loads (or other

operating system shell In computing, a shell is a computer program that exposes an operating system's services to a human user or other programs. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending ...

if specified). # Displays the

bootsplash A bootsplash, also known as a bootscreen, is a graphical representation of the boot process of the operating system. A bootsplash can be a simple visualization of the scrolling boot messages in the console, but it can also present graphics or so ...

in Windows 9x. If is present, it is used as the bootsplash. Otherwise, the bootsplash in is used. The filename was also used by (DCP), an MS-DOS derivative 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, sev ...

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 ...

and

DR DOS DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-DO ...

use the file for the same purpose; it in turn loads . In Windows 9x, the not only contains 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 communicatio ...

, but also holds the DOS kernel, which previously resided in . Under some conditions, Windows 9x uses the alternative filenames or instead. When Windows 9x is installed over a preexisting DOS install, the Windows file may be temporarily named for as long as Windows' dual-boot feature has booted the previous OS. Likewise, the of the older system is named for as long as Windows 9x is active.

DR-DOS 7.06 DR-DOS (written as DR DOS, without a hyphen, in versions up to and including 6.0) is a disk operating system for IBM PC compatibles. Upon its introduction in 1988, it was the first DOS attempting to be compatible with IBM PC DOS and MS-D ...

(only this version) also follows this scheme and the filename in order to become bootable via MS-DOS boot sectors. Similarly,

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 system, legacy software and supporting embedded system ...

uses a combined system file as well, but names it .

Disk layout requirements

* The two first entries of the root directory must be allocated by and , in that order. * must be the first file stored in the -->FAT directory table for files. * The files and must be

contiguous Contiguity or contiguous may refer to: *Contiguous data storage, in computer science *Contiguity (probability theory) *Contiguity (psychology) *Contiguous distribution of species, in biogeography *Geographic contiguity of territorial land *Contigu ...

. However, MS-DOS version 3.3 allows sector 4 and higher to be fragmented; version 5.0 allows the first 3 sectors of to be allocated anywhere (as long as they are contiguous). can be treated like any ordinary file.

Notes

References

DOS files {{Windows-stub

Boot sequence

Disk layout requirements

See also

Notes

References