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Introduction | Chronology | Construction | Operatingsystems | Programming | Pioneers | Companies


We all know a PC, probably heard of supercomputers. But mainframes are not so known.

When you watch television and see a movie with a big machine, or hear people talking to each other (at college) about a mainframe do you sometimes wonder what that is? What they are talking about? Then this page is intended for you.

This page is the first in a future series to explain what a mainframe is and how it evolved in history. Who were the pioneers and what companies were, and still are, involved.

How did and how do they look like? On this page are a few pictures of the earliest mainframes.

Mark I mainframe (1950's)

When you think of a mainframe do you think of a large computer? Right!

But how large is it and what does it do, and what is its place in the family of computers we know

Quantum computers
Grid computers
Mini computers
Embedded computers

The ranking of a mainframe is as you can see almost at the top.

A mainframe is simply a very large computer. And totally different from what you have on your desk. Don't say: what seems to be a mainframe today is on your desktop tomorrow. Apart from the CPU's (processors) that is far from true.

Eniac (1946)

Mainframe is an industry term for a large computer. The name comes from the way the machine is build up: all units (processing, communication etc.) were hung into a frame. Thus the maincomputer is build into a frame, therefore: Mainframe

And because of the sheer development costs, mainframes are typically manufactured by a large company such as IBM, Amdahl, Hitachi.

Their main purpose is to run commercial applications of Fortune 1000 businesses and other large-scale computing purposes.
Think here of banking and insurance businesses where enormous amounts of data are processed, typically (at least) millions of records, each day.


But what classifies a computer as a mainframe?

Historically, a mainframe is associated with centralized computing opposite from distributed computing. Meaning all computing takes (physically) place on the mainframe itself: the processor section.

IBM 4381 mainframe processor from 1985



Building mainframes started with the MarkI soon to be followed by tens of other types and manufacturers. But as said earlier, because of the development costs only governments and large firms could pay for the development of such behemoths.

Have a look at some early mainframes:

Mainframe Year
ENIAC 1942
MarkI 1944
BINAC 1949
Whirlwind 1960
IBM 701 1953
IBM 360 1963



Atanasoff-Berry Computer created at Iowa State



Konrad Zuse -Z2 uses telephone relays instead of mechanical logical circuits





Colossus - British vacuum tube computer



Manchester Mark1



J. Presper Eckert & John Mauchly, ACM, AEEI, ENIAC




Harvard Mark II (Magnetic Drum Storage)




Whirlwind at MIT

Manchester Mark I (1st stored-program digital computer),


Univac I

Univac I first deliverey to the US Census Bureau



Illiac I, Univac I at Livermore predicts 1952 election, MANIAC built at Los Alamos, AVIDAC built at Argonne




IBM 701



IBM 650 (first mass-produced computer),

FORTRAN developed by John Backus

ORACLE-Oak Ridge Automated Computer And Logical Engine

Texas Instruments introduces the silicon transistor,

Univac II introduced



IBM 704



MANIAC 2, DEUCE (fixed head drum memory), clone of IAS



Nippon Telegraph & Telephone Musasino-1: 1st parametron computer, Jack Kilby-First integrated circuit prototype; Robert Noyce works separately on IC's, NEC 1101 & 1102



Paul Baran at Rand develops packet-switching, NEAC 2201,

Whirlwind-air traffic control,

Livermore Advanced Research Computer (LARC),

Control Data Corporation CDC 1604,

First major international computer conference




IBM Stretch-Multiprogramming


IBM 7090 console



First use of virtual memory in a mainframe computer.(4)

Control Data Corporation opens lab in Chippewa Falls headed by Seymour Cray,

Telestar launched,

Atlas-virtual memory and pipelined operations,

Timesharing-IBM 709 and 7090



IBM 360

IBM 360-third generation computer family.



The Sage System,



From the late 1990's mainframe manufacturers started to leave the mainframe market, thinking mainframe business to be less profitable. And then there was virtually only one of major importance left: IBM. And as the single (most important) manufacturer IBM could dictate its own prices and sales went up as well as profits. Not surprisingly IBM's innovations in new mainframe architecture left the rest far behind.
In due time this was observed by other computer manufacturers and since 2001 competition got stronger again.


In the early days output came via a paper tape.

Later by an array of burning lamps and when the vacuumtube technology became sophisticated enough to build a CRT output came by means of spots on the screen (see williams tube).

Operating systems

At first there was no operating system. Most machines were hard wired. Programming it meant rewiring panels and setting hundreds of switches to have the machine calculate a table.
The next years when programming languages became available and memory was no longer a problem programmers created operating systems. You no longer had to be an electrical engineer to program a machine like that.

That made it possible for scientists and other users to quickly make a program and get the results.

To take care of all this a mainframe needs a sophisticated Operating System.
And as you look at it closely also quite different from what you find on your desktops machine. Almost always text based terminals (no graphics) are connected to it. Also PC's can be connected to a mainframe with a special interface program - often called 3270 emulation.

But a mainframe does have some particular properties:

Operating systems for mainframes are few in number: UNIX, Linux, VMS, Z/OS, Z/VM, VSE/ESA. The latter three are of IBM origin and all three: VMS, Linux and Unix also run on IBM mainframes(2)

However there are some dialects of VMS, Linux, and Unix running on different machines.


Programming mainframes

When the first programming languages like Cobol, Fortran and Algol were created every large company and institution could hire people to do the programming of administration or complicated scientific calculations. The atomic bomb project in Los Alamos was a prime example of doing calculations using computers, without it the project never had succeeded in time.



Many scientists have contributed to the mainframe computer as it is now. Things did not go as smooth and fast as it goes nowadays. Sometimes many items, mechanisms, or materials still had to be invented before things really got on their way. On line memory was a crucial phase in developing large computers. Also when timesharing was invented in the late 60's mainframe use exploded.



To create a mainframe one needed at least a few hundred thousand dollars to build the first types.
Later types of the 60' and 70's required a few million dollars and now depending on what capacities you need mainframes range between two three hundred to several tens of millions
It is reasonable to say that small companies can not afford to spent that kind of money to develop one machine or prototype.

Thus firms like:

Ahmdal (Hitachi)
Comparex (Hitachi)
DEC (Compaq)
ICL (Hitachi)

and the like were the only ones financially capable of developing mainframe machines.

As mainframe markets shrunk some companies were assimilated by their peers and other congregated into even larger firms.



A (modern) mainframe is still a very large machine, sometimes tens of square meters. Has usually more than one processor and loads of memory: often running between a few mega- to several hundreds Gb of RAM.
It has tons of disk space and other storage facilities in large size and quantities that are not normally found with mini or micro computers. And although it looks like hundreds of users are using the machine simultaneously it is all governed by a sophisticated time sharing system, hence: serialization. (per processor)

IBM 701 (1952)

Introduction | Chronology | Construction | Operatingsystems | Programming | Pioneers | Companies


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