File Type Windows System File IconWindows System File
File Format Standard (developed by Microsoft)
Usage Referenced by an application; not meant to be opened manually
Popularity ★ ★ ★ ★ ★  Popular

Stores system settings and variables used by the DOS and Windows operating systems; also contains functions that are used to run the operating system; SYS files typically should not be edited.

IO.SYS is used by DOS and Windows 9x; it contains the default DOS device drivers, the DOS initialization program and processes MSDOS.SYS and CONFIG.SYS files.

MSDOS.SYS contains the core operating system code for DOS, known as the DOS kernel; CONFIG.SYS is the primary configuration file used for the DOS operating system.

Open With

IconMicrosoft Windows


IconParallels Desktop for Mac with Windows installed

Published May 19, 2008
Previous Term.swp  |  .t08Next Term
Information from the PC File Extensions Reference