SOme GENEratioNS OF compUter

The history of computer development is often referred to in reference to the different generations of computing devices. A generation refers to the state of improvement in the product development process.
This term is also used in the different advancements of new computer
technology. With each new generation, the circuitry has gotten smaller
and more advanced than the previous generation before it. As a result of
the miniaturization, speed, power, and computer memory has proportionally increased. New discoveries are constantly being developed that affect the way we live, work and play.
Each generation of computers is characterized by major technological
development that fundamentally changed the way computers operate,
resulting in increasingly smaller, cheaper, more powerful and more
efficient and reliable devices. Read about each generation and the
developments that led to the current devices that we use today.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. A
magnetic drum,also referred to as drum, is a metal cylinder coated with
magnetic iron-oxide material on which data and programs can be stored.
Magnetic drums were once use das a primary storage device but have since
been implemented as auxiliary storage devices.
The tracks on a magnetic drum are assigned to channels located around
the circumference of the drum, forming adjacent circular bands that
wind around the drum. A single drum can have up to 200 tracks. As the
drum rotates at a speed of up to 3,000 rpm, the device's read/write
heads deposit magnetized spots on the drum during the write operation
and sense these spots during a read operation. This action is similar to
that of a magnetic tape or disk drive.
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
to perform operations, and they could only solve one problem at a time.
Machine languages are the only languages understood by computers. While
easily understood by computers, machine languages are almost impossible
for humans to use because they consist entirely of numbers. Computer Programmers, therefore, use either high level programming languages or an assembly language programming.
An assembly language contains the same instructions as a machine
language, but the instructions and variables have names instead of being
just numbers.
Programs written in high level programming languages
retranslated into assembly language or machine language by a compiler.
Assembly language program retranslated into machine language by a
program called an assembler (assembly language compiler).
Every CPU has its own unique machine language. Programs must be
rewritten or recompiled, therefore, to run on different types of
computers. Input was based onpunch card and paper tapes, 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.
Acronym for Electronic Numerical Integrator And Computer, the world's
first operational electronic digital computer, developed by Army
Ordnance to compute World War II ballistic firing tables. The ENIAC,
weighing 30 tons, using 200 kilowatts of electric power and consisting
of 18,000 vacuum tubes,1,500 relays, and hundreds of thousands of
resistors,capacitors, and inductors, was completed in 1945. In addition
to ballistics, the ENIAC's field of application included weather
prediction, atomic-energy calculations, cosmic-ray studies, thermal
ignition,random-number studies, wind-tunnel design, and other scientific
uses. The ENIAC soon became obsolete as the need arose for faster
computing speeds.
Second Generation - 1956-1963: Transistors


Transistors replaced vacuum tubes and ushered in the second generation computer.
Transistor is a device composed of semiconductor material that
amplifies a signal or opens or closes a circuit. Invented in 1947 at
Bell Labs, transistors have become the key ingredient of all digital
circuits, including computers. Today's latest microprocessor contains tens of millions of microscopic transistors.
Prior to the invention of transistors, digital circuits were composed
of vacuum tubes, which had many disadvantages. They were much larger,
required more energy, dissipated more heat, and were more prone to
failures. It's safe to say that without the invention of transistors,
computing as we know it today would not be possible.
The transistor was invented in 1947 but did not see widespread use in
computers until the late 50s. 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.
A nonmetallic chemical element in the carbon family of elements.
Silicon - atomic symbol "Si" - is the second most abundant element in
the earth's crust, surpassed only by oxygen. Silicon does not occur
uncombined in nature. Sand and almost all rocks contain silicon combined
with oxygen, forming silica. When silicon combines with other elements,
such as iron, aluminum or potassium, a silicate is formed. Compounds of
silicon also occur in the atmosphere, natural waters,many plants and in
the bodies of some animals.
Silicon is the basic material used to make computer chips,
transistors, silicon diodes and other electronic circuits and switching
devices because its atomic structure makes the element an ideal
semiconductor. Silicon is commonly doped, or mixed,with other elements,
such as boron, phosphorous and arsenic, to alter its conductive
properties.
A chip is a small piece of semi conducting material(usually silicon)
on which an integrated circuit is embedded. A typical chip is less than
¼-square inches and can contain millions of electronic
components(transistors). Computers consist of many chips placed on
electronic boards called printed circuit boards. There are different
types of chips. For example, CPU chips (also called microprocessors)
contain an entire processing unit, whereas memory chips contain blank
memory.
Semiconductor is a material that is neither a good conductor of
electricity (like copper) nor a good insulator (like rubber). The most
common semiconductor materials are silicon and germanium. These
materials are then doped to create an excess or lack of electrons.
Computer chips, both for CPU and memory, are composed of
semiconductor materials. Semiconductors make it possible to miniaturize
electronic components, such as transistors. Not only does
miniaturization mean that the components take up less space, it also
means that they are faster and require less energy.

Related Article: History Behind It All
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 we rebuilt onto a single silicon chip. A
silicon chip that contains a CPU. In the world of personal
computers,the terms microprocessor and CPU are used interchangeably. At
the heart of all personal computers and most workstations sits a
microprocessor. Microprocessors also control the logic of almost all
digital devices, from clock radios to fuel-injection systems for
automobiles.
Three basic characteristics differentiate microprocessors:

• Instruction Set: The set of instructions that the microprocessor can execute.
  
• Bandwidth: The number of bits processed in a single instruction.
  
• Clock Speed: Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.
  

In both cases, the higher the value, the more powerful the CPU. For
example, a 32-bit microprocessor that runs at 50MHz is more powerful
than a 16-bitmicroprocessor that runs at 25MHz.
What in the first generation filled an entire room could now fit in
the palm of the hand. The Intel 4004chip, 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.
Abbreviation of central processing unit, and pronounced as separate
letters. The CPU is the brains of the computer. Sometimes referred to
simply as the processor or central processor, the CPU is where most
calculations take place. In terms of computing power,the CPU is the most
important element of a computer system.
On large machines, CPUs require one or more printed circuit boards.
On personal computers and small workstations, the CPU is housed in a
single chip called a microprocessor.
Two typical components of a CPU are:

• The arithmetic logic unit (ALU), which performs arithmetic and logical operations.
  
• The control unit, which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.
  

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
GUI's, the mouse and handheld devices
Fifth Generation - Present and Beyond: Artificial Intelligence


Fifth generation computing devices, based on artificial intelligence,
are still in development,though there are some applications, such as
voice recognition, that are being used today.
Artificial Intelligence is the branch of computer science concerned
with making computers behave like humans. The term was coined in 1956 by
John McCarthy at the Massachusetts Institute of Technology. Artificial
intelligence includes:

• Games Playing: programming computers to play games such as chess and checkers
  
• Expert Systems: programming computers to make
  decisions in real-life situations (for example, some expert systems help
  doctors diagnose diseases based on symptoms)
  
• Natural Language: programming computers to understand natural human languages
  
• Neural Networks: Systems that simulate intelligence by attempting to reproduce the types of physical connections that occur in animal brains
  
• Robotics: programming computers to see and hear and react to other sensory stimuli
  

Currently, no computers exhibit full artificial intelligence (that
is, are able to simulate human behavior). The greatest advances have
occurred in the field of games playing. The best computer chess programs
are now capable of beating humans. In May,1997, an IBM super-computer
called Deep Blue defeated world chess champion Gary Kasparov in a chess
match.
In the area of robotics, computers are now widely used in assembly
plants, but they are capable only of very limited tasks. Robots have
great difficulty identifying objects based on appearance or feel, and
they still move and handle objects clumsily.
Natural-language processing offers the greatest potential rewards
because it would allow people to interact with computers without needing
any specialized knowledge. You could simply walk up to a computer and
talk to it. Unfortunately, programming computers to understand natural
languages has proved to be more difficult than originally thought. Some
rudimentary translation systems that translate from one human language
to another are in existence, but they are not nearly as good as human
translators.
There are also voice recognition systems that can convert spoken
sounds into written words, but they do not understand what they are
writing; they simply take dictation. Even these systems are quite
limited -- you must speak slowly and distinctly.
In the early 1980s, expert systems were believed to represent the
future of artificial intelligence and of computers in general. To date,
however, they have not lived up to expectations. Many expert systems
help human experts in such fields as medicine and engineering, but they
are very expensive to produce and are helpful only in special
situations.
Today, the hottest area of artificial intelligence is neural
networks, which are proving successful in an umber of disciplines such
as voice recognition and natural-language processing.
There are several programming languages that are known as AI
languages because they are used almost exclusively for AI applications.
The two most common are LISP and Prolog.oice Recognition


The field of computer science that deals with designing computer
systems that can recognize spoken words. Note that voice recognition
implies only that the computer can take dictation, not that it
understands what is being said. Comprehending human languages falls
under a different field of computer science called natural language
processing. A number of voice recognition systems are available on the
market. The most powerful can recognize thousands of words. However,
they generally require an extended training session during which the
computer system becomes accustomed to a particular voice and accent.Such
systems are said to be speaker dependent.
Many systems also require that the speaker speak slowly and
distinctly and separate each word with a short pause. These systems are
called discrete speech systems. Recently, great strides have been made
in continuous speech systems -- voice recognition systems that allow you
to speak naturally. There are now several continuous-speech systems
available for personal computers.
Because of their limitations and high cost, voice recognition systems
have traditionally been used only in a few specialized situations. For
example, such systems are useful in instances when the user is unable to
use a keyboard to enter data because his or her hands are occupied or
disabled. Instead of typing commands, the user can simply speak into a
headset. Increasingly, however, as the cost decreases and performance
improves, speech recognition systems are entering the mainstream and are
being used as an alternative to keyboards.
The use of parallel processing and superconductors is helping to make
artificial intelligence a reality. Parallel processing is the
simultaneous use of more than one CPU to execute a program. Ideally,
parallel processing makes a program run faster because there are more
engines (CPUs) running it. In practice, it is often difficult to divide a
program in such a way that separate CPUs can execute different portions
without interfering with each other.
Most computers have just one CPU, but some models have several. There
are even computers with thousands of CPUs. With single-CPU computers,
it is possible to perform parallel processing by connecting the
computers in a network. However, this type of parallel processing
requires very sophisticated software called distributed processing
software.
Note that parallel processing differs from multitasking, in which a single CPU executes several programs at once.
Parallel processing is also called parallel computing.
Quantum computation and molecular and nano-technology will radically
change the face of computers in years to come. First proposed in the
1970s, quantum computing relies on quantum physics by taking advantage
of certain quantum physics properties of atoms or nuclei that allow them
to work together as quantum bits, or qubits, to be the computer's
processor and memory. By interacting with each other while being
isolated from the external environment,qubits can perform certain
calculations exponentially faster than conventional computers.
Qubits do not rely on the traditional binary nature of computing.
While traditional computers encode information into bits using binary
numbers, either a 0or 1, and can only do calculations on one set of
numbers at once, quantum computers encode information as a series of
quantum-mechanical states such as spin directions of electrons or
polarization orientations of a photon that might represent a 1 or a 0,
might represent a combination of the two or might represent a number
expressing that the state of the qubit is somewhere between 1 and 0, or a
superposition of many different numbers at once. A quantum computer can
doan arbitrary reversible classical computation on all the numbers
simultaneously, which a binary system cannot do, and also has some
ability to produce interference between various different numbers. By
doing a computation on many different numbers at once,then interfering
the results to get a single answer, a quantum computer has the potential
to be much more powerful than a classical computer of the same size.In
using only a single processing unit, a quantum computer can naturally
perform myriad operations in parallel.
Quantum computing is not well suited for tasks such as word
processing and email, but it is ideal for tasks such as cryptography and
modeling and indexing very large databases.
Nanotechnology is a field of science whose goal is to control
individual atoms and molecules to create computer chips and other
devices that are thousands of times smaller than current technologies
permit. Current manufacturing processes use lithography to imprint
circuits on semiconductor materials. While lithography has improved
dramatically over the last two decades -- to the point where some
manufacturing plants can produce circuits smaller than one micron(1,000
nanometers) -- it still deals with aggregates of millions of atoms. It
is widely believed that lithography is quickly approaching its physical
limits. To continue reducing the size of semiconductors, new
technologies that juggle individual atoms will be necessary. This is the
realm of nanotechnology.
Although research in this field dates back to Richard P. Feynman's
classic talk in 1959, the term nanotechnology was first coined by K.
Eric Drexler in1986 in the book Engines of Creation.
In the popular press, the term nanotechnology is sometimes used to
refer to any sub-micron process,including lithography. Because of this,
many scientists are beginning to use the term molecular nanotechnology
when talking about true nanotechnology at the molecular level.
The goal of fifth-generation computing is to develop devices that
respond to natural language input and are capable of learning and
self-organization.
Here natural language means a human language. For example, English,
French, and Chinese are natural languages. Computer languages, such as
FORTRAN and C,are not.
Probably the single most challenging problem in computer science is
to develop computers that can understand natural languages. So far, the
complete solution to this problem has proved elusive, although great
deal of progress has been made. Fourth-generation languages are the
programming languages closest to natural languages.

title is to big so b carefull try to make lil titel edited

OK nxt time i be carefull

nice info