FreeDos

FreeDOS aims to be a complete, free, 100% MS-DOS compatible operating system (mostly achieved.) Today, FreeDOS is ideal for anyone who wants to bundle a version of DOS without having to pay a royalty for use of DOS. FreeDOS will also work on old hardware, in DOS emulators, and in embedded systems. FreeDOS is also an invaluable resource for people who would like to develop their own operating system. While there are many free operating systems out there, no other free DOS-compatible operating system exists. About