Mainframe is the powerful central
computer (CPU) in a
data processing center, linked to thousands of users through less powerful devices
such as PC workstations or dumb terminals. Usually you won'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
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.
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. IBMís
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
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
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!
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 donít have to sit physically near a Mainframe
CPU to do your work.