This chapter presents a short history of operating systems including the IBM OS/360, which was the operating system for the IBM System/360 family of computers. We discuss the MVS and VM operating systems, which were used on the IBM System/370 mainframe computer. Ken Thompson and Dennis Ritchie developed the popular UNIX operating system at Bell Labs in the early 1970s. This is a multi-user and multitasking operating system, and was written almost entirely in C. DEC developed the VAX/VMS operating system in the late 1970s for its VAX family of minicomputers. Microsoft developed MS/DOS for the IBM personal computer compatibles in 1981, and its Windows operating system was a response to the GUI-driven Apple Macintosh. There is a short discussion on Android and iOS, which are popular operating systems for mobile devices.