MS-DOS Mode
The latest versions of the Windows operating system still incorporate a limited version of MS-DOS, which can run within a window. MS-DOS mode does not require 32-bit drivers and high memory management. This makes it ideal for troubleshooting purposes.
The command.com file contains the code that provides the user interface in MS-DOS. Thus, by running command.com under Windows, you open up a MS-DOS session. You can do that by clicking on the START button, selecting RUN from the start menu, and typing COMMAND. To use a command prompt interface you type a MS-DOS command, such as MEM or FORMAT, at the DOS prompt and press the ENTER button on the keyboard. The operating system then loads and executes the command, and then displays the information on the screen. You can generally use the /? switch for help when unsure of how to use a MS-DOS command, alternatively you can use the MS-DOS HELP command.