Definition of MS-DOS Mode in Network Encyclopedia.
What is MS-DOS mode?
MS-DOS mode was a mode of running Microsoft Windows 95 and Windows 98 in which MS-DOS-based applications can access hardware directly. You can use MS-DOS mode when you have to run stubborn MS-DOS programs that will not run in an MS-DOS window within Windows 95 or Windows 98.

How It Works
To switch to MS-DOS mode from Windows, choose Shutdown from the Start menu, and then choose Restart In MS-DOS Mode. The Windows graphical user interface (GUI) vanishes, leaving only an MS-DOS prompt, which allows you to run a single MS-DOS-based application. A stub of the Windows operating system remains in memory and restores the Windows GUI when you type exit at the MS-DOS prompt