Digital Research DOS, known as DR-DOS, DOS compatible operating system that has been owned by many companies and known by several names over its history. It was originally developed by the makers of CP/M, one of the oldest operating systems for the x86 architecture. DR-DOS was later purchased by Novell and known as Novell DOS. Caldera Systems then bought Novell DOS and renamed it OpenDOS. Caldera then renamed the product back to DR-DOS. Caldera then spun off the company known as Lineo and transferred ownership of DR-DOS to Lineo.