The io.sys file

The ‘io.sys’ file is a hidden system file and it is being used to load the operating system when the computer starts booting.

The earliest operating systems like MS-DOS or Windows 3.1 needed more files for the loading process like msdos.sys and other system files. With the appearance of the newer Windows operating systems, the msdos.sys file was embedded into the io.sys file however the msdos.sys file can still be found on today’s computers in the form of a text file instead of an executable file as it was previously.

The io.sys file contains all the information needed to start your PC and all commands in config.sys and autoexec.bat files are now merged into the single io.sys file.  

The io.sys file is an executable and can not be edited as a standard text file. It is usually being managed with the help of the config.sys file.