A Unix-like real-time operating system from RadiSys Corporation, Hillsboro, OR (www.radisys.com) that is widely used in embedded systems such as pagers and cellular phones. OS-9 runs on Motorola 68000 and PowerPC CPUs. Designed initially for the 6809 chip, a version of OS-9 was created for CD-I players. The original developer of OS-9 was Microware Systems Corporation, which RadiSys acquired in 2001. See DAVID.