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The history of operating systems running on IBM mainframes is a notable chapter of history of mainframe operating systems, because of IBM's long-standing position as the world's largest hardware supplier of mainframe computers. Arguably the operating systems which IBM supplied to customers for use on its early mainframes have seldom been very innovative, except for the virtual machine systems beginning with CP-67. But the company's well-known reputation for preferring proven technology has generally given potential users the confidence to adopt new IBM systems fairly quickly. IBM's current mainframe operating systems, z/OS, z/VM, z/VSE, and z/TPF, are backwards compatible successors to operating systems introduced in the 1960s, although of course they have been improved in many ways. Both IBM-supplied operating systems and those supplied by others are discussed here, if notably used on IBM mainframes. ==Before System/360== IBM was slow to introduce operating systems: General Motors produced General Motors OS in 1955 and GM-NAA I/O in 1956 for use on its own IBM computers; and in 1962 Burroughs Corporation released MCP and General Electric introduced GECOS, in both cases for use by their customers.〔(【引用サイトリンク】 title=Timeline of Computer History: 1956: Software )〕〔(OS History - MCP )〕 In fact the first operating systems for IBM computers were written by IBM customers who did not wish to have their very expensive machines (US$2M in the mid-1950s) sitting idle while operators set up jobs manually, and so they wanted a mechanism for maintaining a queue of jobs.〔(A Brief History of Linux )〕 The operating systems described below ran only on a few processor models and were suitable only for scientific and engineering calculations. Users with other IBM computers or other applications had to manage without operating systems. But one of IBM's smaller computers, the IBM 650, introduced a feature which later became part of OS/360: if processing was interrupted by a "random processing error" (hardware glitch), the machine could automatically resume from the last checkpoint instead of requiring the operators to restart the job manually from the beginning.〔(IBM 650 Magnetic Drum Data Processing Machine )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「History of IBM mainframe operating systems」の詳細全文を読む スポンサード リンク
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