Description

A large computer (English: Mainframe, host, Numbercruncher) is a very complex and extensive computer system, which goes the far over capacities personnel of a computer, and often even over those of the typical server systems, outside.

A large computer is characterised particularly by its reliability and high expenditure for in. It can serve a large number of users in on-line operation (Time sharing), in the batch operating in addition, complicated and tasks to accomplish. The users receive entrance to a large computer with on-line operation over Computer-Terminals. Since computers became generally accepted personnel, these terminals are simulated by so-called terminal emulations.

In a large computer components co-ordinated carefully one on the other are blocked, which are high-grade redundant and durable. Usually will maintenance of these computers during operation accomplished, even armaments and hardware exchange can without an interruption of the enterprise be accomplished.

Range of application

Contrary to supercomputers, which are designed for high arithmetic performance, a large computer on reliability and high information flow-rate is optimized. Typical applications of a large computer are in banks, insurance, large enterprises and in the administration. A new operational area for large computers is the consolidation of server farms. With a large computer and a modern operating system it is possible to start many virtual servers. So one can save river, place and administration costs.

For many tasks, with which increased reliability is necessary, but a large computer oversized or technically unsuitable would be, also middle data processing technology so mentioned used, e.g. on the basis of OS/400, VMS or UNIX.

History

Large computers held introduction in research establishments with the invention of the transistor in the middle of the 50's first mainly for instance for the solution of differential equations. There you stressed usually a whole area for itself alone, which was specially air-conditioned around the heat development of the equipment against to work. The function mode was at that time into the following: An operator brought punched arithmetic problems on punch cards to equipment, which read the punch cards in and which collected on a magnetic tape stored data. Another operator brought this magnetic tape to the actual central processor to that the magnetic tape processed and the expenditure on another magnetic tape stored. A further operator brought the magnetic tape with the results to a printer to which the data of the magnetic tape on paper transferred.

Center of the 60's was introduced so-called multiprogramming (multiprogramming), what could exist still to approx. 1980. One had determined with the old method the CCU was mostly not used, since for in and output operations of the volumes had to wait you to you your next order process could. Thus one divided main storage into subranges and could so several volumes quasi at the same time work on.

In approximately to this time most computer manufacturers had developed two to each other incompatible systems. - Word-oriented large computers for the technical-industrial range - indication-oriented large computers for the commercial range

IBM united as first manufacturers both ranges of application and developed as it were the "“first operating system"”, which functioned on the whole product series. There were thus large computers with different achievement (hardware) however such Software.Das system was much successful - successors one finds even today still occasionally with banks. however was e.g. the operating system very extensive and also very therefore maintenance needy.

In the last years manufacturers try such as Sun or Hewlett-Packard (with "“supercathedrals"”), to penetrate with special systems on UNIX basis into the market segment of large computers.

Operating systems: z/OS, MVS, DOS/VSE, z/VM, Multics, OS/360, OS/390, TPF, UNIVAC 1100/2200, BS2000 and lately also Linux (on host operating system)

Manufacturer: Amdahl corporation, Hitachi, IBM, Fujitsu Siemens, Unisys, historically: Robotron/ESER

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