MSDOS.SYS

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MSDOS.SYS is an important system file on MS-DOS and Windows 9x systems. It is loaded by IO.SYS.

In MS-DOS, it contains the core operating system code, the DOS kernel.

Since MS-DOS 7.0, the DOS kernel code has been combined into IO.SYS (aka WINBOOT.SYS), and MSDOS.SYS has become an ASCII 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.

Some pre-DOS 7 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 MS-DOS 7.0.

By default, the file is located in the root directory of the bootable drive/partition (normally C:\) and has the hidden, read-only, and system file attributes set.

IBM PC DOS as well as DR DOS since 5.0 (with the exception of DR-DOS 7.06) used the file IBMDOS.COM for the same purpose, whereas DR DOS 3.31 to 3.41 used DRBDOS.SYS instead.

Windows NT-based operating systems (NT 3.1-4, 2000, XP, and 2003) use the NTLDR file and NT 6+ (Vista, 2008, and 7) uses bootmgr instead, as they have a different boot sequence.

See also

External links

MSDOS.SYS in Windows 9x (95/98/ME):

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