FreeDOS (formerly Free-DOS and PD-DOS) is a free operating system for IBM PC compatible computers. It intends to provide a complete DOS-compatible environment for running legacy software and supporting embedded systems.
FreeDOS can be booted from a floppy disk or USB flash drive. It is designed to run well under virtualization or x86 emulation.
Unlike most versions of MS-DOS, FreeDOS is composed of free and open-source software, licensed under the terms of the GNU General Public License. Therefore, its base distribution does not require license fees or royalties and creation of custom distributions is permitted. However, other packages that form part of the FreeDOS project include non-GPL software considered worth preserving, such as 4DOS, which is distributed under a modified MIT License.