Information and help with the io.sys file

Updated: 01/24/2018 by Computer Hope

What is the io.sys file?

io.sys files helpThe io.sys file is an MS-DOS and Windows 9x hidden system file that is used to load the operating system each time the computer boots. Computers running MS-DOS with our without Windows 3.x required the io.sys and msdos.sys as well as other system files to load MS-DOS.

With the introduction of Microsoft Windows 95 the executable msdos.sys file was merged into the io.sys file and was still a required file to boot the computer into Windows 95 and Windows 98. The msdos.sys file can still exist on computers running either of these versions of Windows, however, it is now a configuration text file and not an executable file.

Later versions of Windows no longer required this file to boot and do not have the option to boot into MS-DOS. However, the file can still be found on Windows ME computers for users that need to create a bootable diskette.

How can I edit the io.sys file?

The io.sys file is an executable file and cannot be edited by a standard text editor. If you do edit the file, it will appear as garbage.

Any configuration settings that may need to be done in the io.sys are handled through the config.sys file. See the autoexec.bat and config.sys page for additional help and information with these files.

Microsoft Windows 9x users can also configure additional settings through the msdos.sys file, which as mentioned above is a configurable text file in these versions of Windows.

I need the io.sys file for a bootable diskette.

See the bootable diskette page for additional information about creating boot diskettes and sites where you can download files required for bootable diskettes.

Can you send me the io.sys file or can I download it?

Because of Copyright restrictions we cannot send users the io.sys or make it available for download.

Additional information