Computer is a
machine that manipulates data according to a set of instructions.
Although mechanical examples of computers have existed through much of
recorded human history, the first electronic computers were developed in
the mid-20th century (1940–1945). These were the size of a large room,
consuming as much power as several hundred modern personal computers.
Modern computers based on integrated circuits are millions to billions
of times more capable than the early machines, and occupy a fraction of
the space.Simple computers are small enough to fit into a wristwatch,
and can be powered by a watch battery. Personal computers in their
various forms are icons of the Information Age and are what most people
think of as "computers". The embedded computers found in many devices
from MP3 players to fighter aircraft and from toys to industrial robots
are however the most numerous.
Technically,
a computer is a programmable machine. The ability to store and execute
lists of instructions called programs makes computers extremely
versatile, distinguishing them from calculators. This means it can
execute a programmed list of instructions and respond to new
instructions that it is given. When referring to a desktop model, the
term "computer" technically only refers to the computer itself -- not
the monitor, keyboard, and mouse. Still, it is acceptable to refer to
everything together as the computer. If you want to be really technical,
the box that holds the computer is called the "system unit."
Some
of the major parts of a personal computer (or PC) include the
motherboard, CPU, memory (or RAM), hard drive, and video card. While
personal computers are by far the most common type of computers today,
there are several other types of computers. For example, a
"minicomputer" is a powerful computer that can support many users at
once. A "mainframe" is a large, high-powered computer that can perform
billions of calculations from multiple sources at one time. Finally, a
"supercomputer" is a machine that can process billions of instructions a
second and is used to calculate extremely complex calculations.
There are five generations of computer that are given below
First Generation (1940-1956) Vacuum Tubes
The
first computers used vacuum tubes for circuitry and magnetic drums for
memory, and were often enormous, taking up entire rooms. They were very
expensive to operate and in addition to using a great deal of
electricity, generated a lot of heat, which was often the cause of
malfunctions.
First
generation computers relied on machine language, the lowest-level
programming language understood by computers, to perform operations, and
they could only solve one problem at a time. Input was based on punched
cards and paper tape, and output was displayed on printouts.
The
UNIVAC and ENIAC computers are examples of first-generation computing
devices. The UNIVAC was the first commercial computer delivered to a
business client, the U.S. Census Bureau in 1951.
Second Generation (1956-1963) Transistors
Transistors
replaced vacuum tubes and ushered in the second generation of
computers. The transistor was invented in 1947 but did not see
widespread use in computers until the late 1950s. The transistor was far
superior to the vacuum tube, allowing computers to become smaller,
faster, cheaper, more energy-efficient and more reliable than their
first-generation predecessors. Though the transistor still generated a
great deal of heat that subjected the computer to damage, it was a vast
improvement over the vacuum tube. Second-generation computers still
relied on punched cards for input and printouts for output.
Second-generation computers moved from cryptic binary machine language
to symbolic, or assembly, languages, which allowed programmers to
specify instructions in words. High-level programming languages were
also being developed at this time, such as early versions of COBOL and
FORTRAN. These were also the first computers that stored their
instructions in their memory, which moved from a magnetic drum to
magnetic core technology.
The first computers of this generation were developed for the atomic energy industry.
Third Generation (1964-1971) Integrated Circuits
The
development of the integrated circuit was the hallmark of the third
generation of computers. Transistors were miniaturized and placed on
silicon chips, called semiconductors, which drastically increased the
speed and efficiency of computers.
Instead
of punched cards and printouts, users interacted with third generation
computers through keyboards and monitors and interfaced with an
operating system, which allowed the device to run many different
applications at one time with a central program that monitored the
memory. Computers for the first time became accessible to a mass
audience because they were smaller and cheaper than their predecessors.
Fourth Generation (1971-Present) Microprocessors
The
microprocessor brought the fourth generation of computers, as thousands
of integrated circuits were built onto a single silicon chip. What in
the first generation filled an entire room could now fit in the palm of
the hand. The Intel 4004 chip, developed in 1971, located all the
components of the computer—from the central processing unit and memory
to input/output controls—on a single chip.
In
1981 IBM introduced its first computer for the home user, and in 1984
Apple introduced the Macintosh. Microprocessors also moved out of the
realm of desktop computers and into many areas of life as more and more
everyday products began to use microprocessors.
As
these small computers became more powerful, they could be linked
together to form networks, which eventually led to the development of
the Internet. Fourth generation computers also saw the development of
GUIs, the mouse and handheld devices.
