Computer Operating Systems
In early computer systems, a human operator monitored operations, determined the order of programs to run, and handled all input and output processes. However, much time was wasted when a program would end its run, and the entire system sat idle while the operator prepared the next job. As computer processing speeds increased, the use of human operators became unrealistic. The need for more efficient use of computer resources resulted in the development of operating systems, which act somewhat like traffic directors for the computer. Operating systems are a collection of programs designed to permit a computer to manage its own operations, including peripherals (printers and modems), programs, and data. In 1954 Gene Amdahl (1922-) developed the first operating system, which was used on an IBM 704. In 1961 Frederick Brookes (1931-), an IBM engineer, began developing an operating system for the IBM S/360. By 1965 Brookes's development team consisted of 2,000 programmers with a budget of $60 million. The resultant operating system, known as OS/360, was a well designed, efficient program that became an industry standard for the next several decades. It was the largest software development project ever attempted and remained so through the mid-1980s. OS/360 also served as the basis for other mainframe computer software developed in the 1980s, such as DOS/VS, MVS/XA, and OS/VS. Generally, systems software is developed for a particular type of computer processor chip or to meet a particular function.
UNIX, developed in 1971 by Ken Thompson (1917-) and Denis Ritchie at Bell Laboratories, has become the dominant operating system of the late 1980s and early 1990s. Usable on mainframes, minicomputers and even microcomputers, UNIX is often the preferred operating system for network use. Another mainframe system, PICK, developed by Dick Pick, also goes by the name REALITY, PRIME-INFORMATION or ULTIMATE, depending upon the type of computer it is used on. When microcomputers were introduced in the early 1970s, almost all ran under the CP/M operating system, written in 1973 by Gary Kildall. Soon after its introduction, the CP/M system was overtaken completely by MS-DOS, an operating system from Microsoft Corporation and its founder William Gates. The earliest version of MS-DOS was based on a product from Seattle Computer Products known as 86-DOS, which was basically an enhanced version of CP/M. Many powerful features have been added to MS-DOS and current versions bear little resemblance to the first product. Some newer operating systems, including OS/2 introduced in 1987 by Microsoft and IBM, have been hailed as the next industry standard; however, users were slow to accept a replacement for DOS. Microsoft enhanced MS-DOS over the years and eventually created a graphical user interface called Windows. Windows was a success in that it hid the complexities of MS-DOS behind on-screen graphics and the use of a mouse. But acceptance of Windows was slow until 1995 when Microsoft released Windows 95. Windows 95 was more than a thin shell over MS-DOS, it was in its own right an operating system. Windows software from Microsoft is now used on over 90% of the computers on the planet.
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