(1) (OS 9) See macOS.
(2) A Unix-like real-time operating system from Microware LP (www.microware.com) that is widely used in embedded systems. Originally developed as a Motorola 6809 assembly language, the version written in C runs on PowerPC, x86, ARM and other CPUs. OS-9 was also used for CD-I players. The original developer of OS-9 was Microware Systems Corporation, which RadiSys acquired in 2001. In 2013, RadiSys sold OS-9 to Microware LP, a joint venture of the resellers of the software. See CD-I and DAVID.