UNIX(R) Time Sharing or Real Time?

Originally conceived as a pure time sharing development environment, the UNIX(R) operating system has developed over the years into a run-time environment as well. This transition involved a change in emphasis from a set of isolated independent processes, each of which appeared to have access to the entire set of system resources, to a set of cooperating processes required to share control flow information and data, with engineered partition of system resources.