FreeDOS is a free DOS-compatible operating system for IBM-PC compatible systems. FreeDOS is made of up many different, separate programs that act as "packages" to the overall FreeDOS Project.

These days, there are three main uses of FreeDOS:
To run old DOS games (like DOOM, etc.)
To run old business software that only supports DOS
To support an embedded DOS system, such as a computerized cash register or till

You can run FreeDOS on pretty much anything. While can run FreeDOS on a dedicated PC, now it's most often run inside a PC emulator. You can find PC emulators for all computer platforms (Windows, Linux, Mac.) If you are new to DOS, we recommend you use an emulator to install and boot FreeDOS.

http://www.freedos.org/