The ReactOS project develops a open source operating system which attempts to be binary compatible with Microsoft Windows, allowing ReactOS users to run Windows programs. The ReactOS project recently updated their build insructions to indicate ReactOS is able to build itself without the aid of another operating system. This is a significant milestone for operating systems as it allows developers to work on a system while running the system. A related tweet reads: "Now, ReactOS can fully build ReactOS, even with the USB stack. Be it a LiveCD or a BootCD!"