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Revision as of 17:06, 21 August 2005 by 70.217.114.184 (talk) (added a little more detail, links)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)An IBM mainframe is an International Business Machines (IBM)-made mainframe computer, i.e. a traditionally "large," high-performance computer (in terms of price tag, physical size, transaction processing and I/O performance), although usually not as expensive and highly performing as a supercomputer.
Description
In the early years (1950 to 1965), IBM and several other companies manufactured numerous computer models, most of which were incompatible with each other. IBM had two model categories: one for commercial or data processing use, and another one for engineering and scientific use. The two categories were largely incompatible with each other, and there were incompatibilities even within each category. All that changed with the announcement of the System/360 (S/360) in April, 1964 — exactly when the Beatles first became popular in America. The System/360 was a single series of compatible models for both commercial and scientific use. (NASA became a big System/360 scientific customer.) The System/360 later evolved into the System/370, the System/390, the zSeries, and today's System z9.
System/360 (the "360 degree," i.e. "all-around" computer system) incorporated into a single architecture features which had previously been present on only the commercial (decimal arithmetic, for example, or byte addressing) or the technical (floating point arithmetic) lines of machines.¹ The System/360 was also the first computer architecture in wide use to include dedicated hardware provisions for the use of operating systems. Among these were the notion of supervisor and application mode programs and instructions, as well as built-in memory protection facilities.²
Notable pre-System/360 IBM mainframes included:
Operating systems
The primary operating systems in use on today's IBM mainframes include z/OS (which followed MVS and OS/390), z/VM (previously VM/CMS), z/VSE, z/TPF, and Linux on zSeries. (A few systems still run MUSIC/SP, another operating system.) Previous operating systems for the System/360 family and its successors included OS/360 (with PCP, MFT, and MVT), BOS, TOS, DOS, and SVS. There are software-based emulators for the System/370, System/390, zSeries, and System z9 hardware, including FLEX-ES and the freely available Hercules emulator which runs under Linux and Microsoft Windows. The original OS/360 and early MVS and VM/CMS versions have been released for free use.
Middleware
IBM mainframes run all the major enterprise transaction processing environments and databases, including CICS, IMS, WebSphere Application Server, DB2, and Oracle. In many cases these software subsystems can run on more than one mainframe operating system.
See also
References
- Prasad, Nallur, IBM Mainframes: Architecture and Design, 2nd ed., 1994. McGraw-Hill Osborne Media, ISBN 0070506914.³
External links
Footnotes
¹ Some of the arithmetic units and addressing features were optional on some models of the System/360. However, models were upward compatible and most were also downward compatible.
² Hardware memory protection was provided to protect the operating system from the user programs (tasks) and the user tasks from each other.
³ Now dated. For details on the significant 64-bit architectural changes, refer to IBM technical publications. (See z/Architecture.)