The FreeDOS Project, 2012. DOS.
FreeDOS is a free operating system compatible with MS-DOS. Jim Hall, then a student, started the project on 29 June 1994, after Microsoft announced it would no longer sell or support MS-DOS. He posted a proposal for a public-domain DOS, at first called PD-DOS.
Within a few weeks other programmers joined him. Pat Villani wrote the kernel, Villani and Tim Norman the COMMAND.COM command interpreter, and Hall the core utilities, pooling code they had written or found. The first stable version, FreeDOS 1.0, came out in 2006.
FreeDOS is licensed under the GNU GPL, with some packages under other licenses. It runs on a PC/XT with 640 KB of memory. Dell and HP have shipped it on computers, and it is a common choice for BIOS update disks. Today the project describes it as a way to play classic DOS games, run legacy business software, and write new DOS programs.
This exhibit boots a 720 KB floppy with FreeDOS kernel build 2040, compiled in April 2012, and the FreeCOM 0.82 command shell from December 2003. Its welcome message suggests three games to try: invaders, snake and tetris.