Wikipedia of IBM Mainframe Computers

Mainframe Basics

IBM z15 Mainframe
Mainframe is the powerful central computer (CPU) in a data processing center, linked to thousands of users through less powerful devicessuch as PC workstations or terminals(just monitor and keyboard). Usually you don't find a mainframe in any household or small companies.

However, in the mid-1950s, all computers were mainframes, since the term 'mainframe' referred to the main CPU frame. In those days, mainframe computers were not just the largest computers; they were the only computers. Several manufacturers like IBM, Honeywell, Burroughs produced mainframe computers from the late 1950s. From the 1970s, the term Mainframe Computer was almost synonymous with IBM products due to their market share.

In the hierarchy of computers, mainframes are right below supercomputers, the most powerful computers in the world. (Which is why they are aptly named "supercomputers.") Yet a mainframe can usually execute many programs simultaneously at a high speed, whereas supercomputers are designed to execute a single process at the highest speed. The ability of Mainframes are often measured in millions of instructions per second (MIPS), but supercomputers are measured in floating point operations per second (FLOPS). Commonly supercomputers are used for scientific problems, while mainframes are used for business processing.


Mainframe History

  • Some of the early mainframes which were developed starting from the year of 1942 are ENIAC, MARK1, BINAC, UNIVAC. ENIAC is also called as electronic numerical integrator and calculator. In the year 1951, UNIVAC-I was developed specially for the US Census Bureau. The major difference between UNIVAC and ENIAC was the processing of digits.
  • The first IBM mainframes like IBM 701/704 were designed to serve war clients like the US Department of Defense. IBM initially sold its computers without any software, expecting customers to write their own. Later, IBM provided compilers for the newly developed higher-level programming languages Fortran and COBOL.
  • The original mainframes were housed in room-sized metal frames, which is probably where the name derives from. In the past, a typical mainframe might have occupied 10,000 square feet. They required large amounts of electrical power and air-conditioning, and the room was filled mainly with I/O devices.
  • On April 7, 1964, IBM unveiled System/360. Costing $5 billion dollars, this computer system revolutionized the IT industry, allowing customers to consolidate all of their data and applications onto a single system. IBM's computer business continued to grow in the 1970s, introducing the next generation of mainframes, System/370, and later the 64K RAM chip. This would not be large enough to hold a standard sized digital photograph today, but it allowed customers at the time to support even more applications on a single machine.
  • In September 1990, IBM introduced the S/390, a family of 18 new systems with 10 air-cooled models, and eight water-cooled models.
  • Newer mainframes are about the same size as a large refrigerator. Today, computer manufacturers don't always use the term mainframe to refer to mainframe computers. Instead, most have taken to calling any commercial use computer- large or small- a server, with the mainframe simply being the largest type of server in use today. IBM, for example, refers to its latest mainframe as the IBM z13 server.
  • Mainframe Computer acts as a central CPU. In olden days, IBM Terminals connected to the mainframe remotely, over a network. They used the IBM 3270 protocol for communication. IBM no longer manufactures terminals, instead we can use a normal PC running a software(called as Emulator) that mimics the IBM 3270 terminal.
  • Currently, the largest manufacturers of mainframes are IBM and Unisys. With trillions of dollars worth of IBM mainframe applications in place, mainframes may hang around for quite a while. Some even predict they are the wave of the future!

  • The Mainframe Story

    One common impression of a mainframe's user interface is the 80x24-character "green screen" terminal, named for the old cathode ray tube (CRT) monitors from years ago that glowed green. In reality, mainframe interfaces today look much the same as those for personal computers. When a business application is accessed through a Web browser, there is often a mainframe computer performing crucial functions behind the scenes.

    Now a days, people around the world connect to the Mainframe Computer, remotely over internet, from their work-place or home using a PC running a software that pretends to be a dumb-terminal. You don't have to sit physically near a Mainframe CPU to do your work.

    Next Article: Who uses Mainframes



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