Operating Systems
...e computer (usually an IBM 7094), eliminating the need to swap tapes or cards between programs. The first operating system was designed by General Motors for the IBM 701. It was called Input/Output System, and consisted of a small set of code that provided a common set of procedures to be used to access the input and output devices. It also allowed each program to access the code when finished and accepted and loaded the next program. However, there was a need to improve the sharing of programs, which led to the development of the SOS (Share operating system), in 1959. The SOS provided buffer management and supervision for I/O devices as well as support for programming in assembly language. Around the same time as SOS was being developed, the first operating system to support programming in a high?level language was achieved. FMS (Fortran Monitoring System) incorporated a translator for IBM's FORTRAN language, which was widely used as most programs where written in this language. Third Generation Computers (1965?1980) In the late 1960's IBM created the System/360 which was a series of software compatible computers ranging in different power of performance and price. The machines had the same architecture and instruction set, which allowed programs written for one machine to be executed on another. The operating system required to run on this family of computers has to be able to work on all models, be backwards compatible and be able to run on both small and large systems. The software written to handle these different requirements was OS/360, which consisted of millions of lines of assembly language written by thousands of different programmers. It also contained thousands of bugs, but despite this the operating system satisfactory fulfilled the requirements of most users. A major feature of the new operating system was the ability to implement multiprogramming. By partitioning the memory into several pieces, programmers where able to use the CPU more effectively then ever before, as a job could be processed whilst another was waiting for I/O to finish. Spooling was another important feature implemented in third generation operating systems. Spooling (Simultaneous Peripheral Operation On?Line) was is ability to load a new program into an empty partition of memory when a pervious job had finished. This technique meant that the IBM 1401 computer was no longer required to read the program from the magnetic tape. mission of a job and returning of results had increased. This led designers to the concept of time?sharing, which involved each user communicating with the computer through an their own on?line terminal. The SPU could only be allocated to 3 terminals, each job held in a partition of memory. Many time?sharing operating systems were introduced in the 1960's, including the MULTICS (Multiplexed Information and Computing Service). Developed by Bell Labs, MULTICS was written almost completely in high?level language, and is known as the first major operating system to have done so. MULTICS examined many new concepts including segmented memory, device independence, hierarchal file system, I/O redirection, a powerful user interface and protection rings. The 1960's also gave rise to the minicomputer, starting with the DEC PDP?1. Minicomputers presented the market with an affordable alternative to the large batch systems of that time, but had only a small amount of memory. The early operating system of the minicomputers were Input/Output selectors, and provided an interactive user interface for a single user, and ran only one program at a time. By the 1970's, DEC introduced a new family of minicomputers. The PDP?11 series had 3 operating systems available to use on the systems, a simple single user system (RT?11), a time sharing system (RSTS) and a real?time system (RSX?11). RSX?11 was the most advanced operating system for the PDP?11 series. It supported a powerful command language and file system, memory management and muiltprogramming a number of tasks. Around the same time as DEC were implementing their minicomputers, two researchers, ken Thomspson and Dennis Richie were developing a new operating system for the DEC PDP?7. Their aim was to create a new single?user operating, and the first version was officially released in 1971. This operating system, called UNIX became very popular and is still used widely today. Fourth Generation Computers (1980?1990) By the 1980's, technology had advanced a great deal from the days of the mainframe computers and vacuum tubes. With the introduction of Large Scale Integration circuits (LSI) and silicon chips consisting of thousands of transistors, computers reached a new level. Microcomputers, which were physically much like the minicomputers of the third generation, however they were much cheaper enabling individuals to now use them, not just large company's and universities. These personal computers and required an operating system that was user friendly so that people with little computer knowledge was able to use it. In 1981, IBM was releasing a 16?bit personal computer, and required a more powerful operating system then the ones available at the time, so they turned to Microsoft to deliver it. The software, called Micro Soft Disk Operating System (MS?DOS) became the standard operating system for most personal computers of that era. In the mid?1980's, networks of personal computers had increased a great deal, requiring a new type of operating system. The OS had to be able to manage remote and local hardware and software, file sharing and protection, among other things. Two types of systems were introduced, the network operating...