Reference number: CH000872

Information and help with the io.sys file.

Question:

Information and help with the io.sys file.

Answer:

What is the io.sys file?

The io.sys file is a 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 in order 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 or Windows 98. The msdos.sys file can still exist on computers running either of these versions of Windows however 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 attempt to edit the file it will only appear as a bunch of symbols and unreadable characters.

Any configuration settings that may need to be done in the io.sys are handled through the config.sys file. See our 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 our 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.