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FUNDAMENTALS, BASIC CONCEPT OF COMPUTER
COMPUTER
Definition
A computer is a machine that can be programmed to manipulate symbols. Its principal
characteristics are:



It responds to a specific set of instructions in a well-defined manner.
It can execute a prerecorded list of instructions (a program).
It can quickly store and retrieve large amounts of data.
OR
A computer is a programmable machine designed to automatically carry out a sequence of
arithmetic or logical operations.
OR
A computer is an electronic device that can transmit, store and manipulate information or data
which can be numeric or character type.
History of Computers
"Computer" was originally a job title; it was used to describe those human beings (predominantly
women) whose job it was to perform the repetitive calculations required to compute such things
as navigational tables, tide charts, and planetary positions for astronomical almanacs.
The abacus was an early aid for mathematical computations. Its only value is that it aids the
memory of the human performing the calculation. A skilled abacus operator can work on
addition and subtraction problems at the speed of a person equipped with a hand calculator
(multiplication and division are slower). The abacus is often wrongly attributed to China. In fact,
the oldest surviving abacus was used in 300 B.C. by the Babylonians. The abacus is still in use
today, principally in the far east. A modern abacus consists of rings that slide over rods, but the
older one pictured below dates from the time when pebbles were used for counting (the word
"calculus" comes from the Latin word for pebble).
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A very old abacus
A more modern abacus.
Note how the abacus is really just a
representation of the human fingers: the 5
lower rings on each rod represent the 5
fingers and the 2 upper rings represent
the 2 hands.
Logarithm Invention: In 1617 an eccentric (some say mad) Scotsman named John Napier
invented logarithms, which are a technology that allows
multiplication to be performed via addition. The magic ingredient
is the logarithm of each operand, which was originally obtained
from a printed table. But Napier also invented an alternative to
tables, where the logarithm values were carved on ivory sticks
which are now called Napier's Bones.
Napier's invention led directly to the slide rule, first built in
England in 1632 and still in use in the 1960's by the NASA
engineers of the Mercury, Gemini, and Apollo programs which landed men on the moon.
An original set of Napier's Bones
A slide rule
more modern set of Napier's
Bones
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Gear-driven calculating machine invention:
Leonardo da Vinci (1452-1519) made drawings of gear-driven calculating machines but
apparently never built any.
The first gear-driven calculating machine to actually be built was
probably the calculating clock, so named by its inventor, the German
professor Wilhelm Schickard in 1623. This device got little publicity
because Schickard died soon afterward in the bubonic plague.
Pascaline Invention:
In 1642 Blaise Pascal, at age 19, invented the Pascaline as an aid for his father who was a tax
collector. Pascal built 50 of this gear-driven one-function calculator (it could only add) but
couldn't sell many because of their exorbitant cost and because they really weren't that accurate
Stepped reckoner invention:
Just a few years after Pascal, the German Gottfried Wilhelm Leibniz (co-inventor with Newton
of calculus) managed to build a four-function (addition, subtraction, multiplication, and division)
calculator that he called the stepped reckoner because, instead
of gears, it employed fluted drums having ten flutes arranged
around their circumference in a stair-step fashion. Although the
stepped reckoner employed the decimal number system (each
drum had 10 flutes), Leibniz was the first to advocate use of the
binary number system which is fundamental to the operation of
modern computers. Leibniz is considered one of the greatest of
the philosophers but he died poor and alone.
Leibniz's Stepped Reckoner
Punched Card invention:
In 1801 the Frenchman Joseph Marie Jacquard invented a power loom that could base its weave
(and hence the design on the fabric) upon a pattern
automatically read from punched wooden cards, held
together in a long row by rope. Descendents of these
punched cards have been in use ever since. Jacquard's
technology was a real boon to mill owners, but put many
loom operators out of work. Angry mobs smashed Jacquard
looms and once attacked Jacquard himself. History is full of
examples of labor unrest following technological innovation
yet most studies show that, overall, technology has actually
increased the number of jobs. `
A close-up of a Jacquard card
By 1822 the English mathematician Charles Babbage was proposing a steam driven calculating
machine the size of a room, which he called the Difference Engine. This machine would be able
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to compute tables of numbers, such as logarithm tables. He obtained government funding for this
project due to the importance of numeric tables in ocean navigation. By promoting their
commercial and military navies, the British government had
managed to become the earth's greatest empire. But in that time
frame the British government was publishing a seven volume set
of navigation tables which came with a companion volume of
corrections which showed that the set had over 1000 numerical
errors. It was hoped that Babbage's machine could eliminate
errors in these types of tables. But construction of Babbage's
Difference Engine proved exceedingly difficult and the project
soon became the most expensive government funded project up
to that point in English history. Ten years later the device was
still nowhere near complete, acrimony abounded between all
involved, and funding dried up. The device was never finished.
Babbage was not deterred, and by then was on to his next
brainstorm, which he called the Analytic Engine. This device, large as a house and powered by 6
steam engines, would be more general purpose in nature because it would be programmable,
thanks to the punched card technology of Jacquard. But it was Babbage who made an important
intellectual leap regarding the punched cards.
Furthermore, Babbage realized that punched paper could be employed as a storage mechanism,
holding computed numbers for future reference. Because of the connection to the Jacquard loom,
Babbage called the two main parts of his Analytic Engine the "Store" and the "Mill", as both
terms are used in the weaving industry. The Store was where numbers were held and the Mill
was where they were "woven" into new results. In a modern computer these same parts are called
the memory unit and the central processing unit (CPU). The Analytic Engine also had a key
function that distinguishes computers from calculators: the conditional statement. A conditional
statement allows a program to achieve different results each time it is run.
IBM invention:
The next breakthrough occurred in America. Hollerith's invention, known as the Hollerith desk,
consisted of a card reader which sensed the holes in the cards, a
gear driven mechanism which could count (using Pascal's
mechanism which we still see in car odometers), and a large wall
of dial indicators (a car speedometer is a dial indicator) to display
the results of the count.
Hollerith's technique was successful and the 1890 census was
completed in only 3 years at a savings of 5 million dollars.
Hollerith built a company, the Tabulating Machine Company
which, after a few buyouts, eventually became International
Business Machines, known today as IBM. IBM grew rapidly and
punched cards became ubiquitous. Your gas bill would arrive each
month with a punch card you had to return with your payment.
This punch card recorded the particulars of your account: your name, address, gas usage, etc. (I
imagine there were some "hackers" in these days who would alter the punch cards to change
their bill).
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IBM continued to develop mechanical calculators for sale to businesses to help with financial
accounting and inventory accounting. One characteristic of both financial accounting and
inventory accounting is that although you need to subtract, you don't need negative numbers and
you really don't have to multiply since multiplication
can be accomplished via repeated addition. But the
U.S. military desired a mechanical calculator more
optimized for scientific computation. One early
success was the Harvard Mark I computer which
was built as a partnership between Harvard and IBM
in 1944. This was the first programmable digital
computer made in the U.S. But it was not a purely
electronic computer. Instead the Mark I was
constructed out of switches, relays, rotating shafts,
and clutches. The machine weighed 5 tons,
incorporated 500 miles of wire, was 8 feet tall and 51
feet long, and had a 50 ft rotating shaft running its length, turned by a 5 horsepower electric
motor. The Mark I ran non-stop for 15 years, sounding like a roomful of ladies knitting. To
appreciate the scale of this machine note the four typewriters in the foreground of the following
photo.
Turing Machine:
Alan Turing of Cambridge university presented his idea(1936) of a theoretically simplified but
fully capable computer, now known as the Turing machine. The concept of this machine, which
could theoretically perform any mathematical computation, was very important in the future
development of the computer. Another contribution by Alan Turing is the Turing test proposed
to determine if a computer has the ability to think. So far no one has built a computer that can
pass that test, there is cash prize of US$ 100,000.
GENERATIONS OF COMPUTER:
Each generation of computer is characterized by a major technological development that
fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper,
more powerful and more efficient and reliable devices. The history of computer development is
often referred to in reference to the different generations of computing devices. Each generation
of computer is characterized by a major technological development that fundamentally changed
the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more
efficient and reliable devices.
1. First generation (1940-1956):
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
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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. The examples are;

ENIAC (1946):
The title of forefather of today's all-electronic digital computers is usually awarded to ENIAC,
which stood for Electronic Numerical Integrator and Calculator. ENIAC was built at the
University of Pennsylvania between 1943 and 1945 by
two professors, John Mauchly and the 24 year old J.
Presper Eckert, who got funding from the war
department after promising they could build a machine
that would replace all the "computers". ENIAC filled a
20 by 40 foot room, weighed 30 tons, and used more
than 18,000 vacuum tubes. Once ENIAC was finished
and proved worthy of the cost of its development, its
designers set about to eliminate the obnoxious fact that
reprogramming the computer required a physical
modification of all the patch cords and switches.
ENIAC

EDVAC (1948):
It took days to change ENIAC's program. Eckert and Mauchly's next teamed up with the
mathematician John von Neumann to design EDVAC, which pioneered the stored program. It
is electronic variable automatic computer, which incorporate a program stored entirely within its
memory.

Floppy disk (1950):
It was invented by Yoshiro nakamats.
compared with magnetic tape.

It provided faster access to programs and data as
Compiler (1951):
Grace hopper of US navy develops the very first high level language compiler. Before the
invention of this compiler, developing a computer program was tedious and prone to errors. A
compiler translates high level language (that is easy to understand for humans) into a language
that the computer can understand.
Other types (1951):
After ENIAC and EDVAC came other computers with humorous names such as ILLIAC,
JOHNNIAC, and, of course, MANIAC. ILLIAC was built at the University of Illinois at
Champaign-Urbana,
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By the end of the 1950's computers were no longer one-of-a-kind hand built devices owned only
by universities and government research labs. Eckert and Mauchly left the University of
Pennsylvania over a dispute about who owned the patents for their invention. They decided to set
up their own company. Their first product was the famous UNIVAC computer, the first
commercial (that is, mass produced) computer. The first UNIVAC was sold, appropriately
enough, to the Census bureau. UNIVAC was also the first computer to employ magnetic tape.
Advantages:


Fastest calculation device
Control electronic signal for calculation
Limitations:

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Too bulky size
Unreliable
Thousand of vacuum tube were used
Air condition system is required
Regular hardware failure
Constant maintainance required
Not portable
Manual assembly
Commercial production was difficult & Limited commercial use
2. Second Generation (1956-1963):
Transistors(1947) replaced vacuum tubes and ushered in the second generation of computers.
The transistor was invented in 1947 by shockly, bardeen and brattain in the bell labs USA 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.
Advantages:



Small in size
More reliable
Less computation time
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Less heat generator
Less prone to hardware failure
Better portability
Wide commercial usage
Limitations:



Air production system is required
Manual assembly
Commercial production was difficult and costly
3. Third Generation (1964-1971):
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. The examples are;

BASIC (1965):
It is developed by Thomas Kurtz and john kemeny at Dartmouth college. It has all purpose
symbolic instruction code.

Computer Mouse (1965):
It was developed by Douglas Englebart. It did not become popular until 1983, when apple
computers adopted the concept.

ARPANET (1969):
It is a network of networks, which is a grand daddy of the today’s global internet. It is a network
of around 60,000 computers developed by the US department of defense to facilitate
communications between research organizations and universities.
Advantages:




Smaller in size as compared to previous generations
More reliable and less heat generation
Easly portable
Maintainance cost is low
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Less power requirement
Totally general purpose
Commercial production was easy and cheap
Limitations:


Air condition system is required
Highly sophisticated technology required for manufacturing the IC’s chips
4. Fourth Generation (1971-Present):
This transformation was a result of the invention of the microprocessor. A microprocessor (uP)
is a computer that is fabricated on an integrated circuit (IC). The microprocessor brought the
fourth generation of computers, as thousands of integrated circuits were built onto a single
silicon chip. Computers had been around for 20 years before the first microprocessor was
developed at Intel in 1971. The micro in the name microprocessor refers to the physical size.
Intel didn't invent the electronic computer. But they were the first to succeed in cramming an
entire computer on a single chip (IC). Intel was started in 1968 and initially produced only
semiconductor memory (Intel invented both the DRAM and the EPROM, two memory
technologies that are still going strong today). In 1969 they were approached by Busicom, a
Japanese manufacturer of high performance calculators (these
were typewriter sized units, the first shirt-pocket sized
scientific calculator was the Hewlett-Packard HP35 introduced
in 1972). Busicom wanted Intel to produce 12 custom
calculator chips: one chip dedicated to the keyboard, another
chip dedicated to the display, another for the printer, etc. But
integrated circuits were (and are) expensive to design and this
approach would have required Busicom to bear the full
expense of developing 12 new chips since these 12 chips would
only be of use to them. The examples are;
A typical Busicom desk calculator
 Intel (1971):
The Intel 4004, the first microprocessor (uP). The 4004 consisted of 2300 transistors and was
clocked at 108 kHz (i.e., 108,000 times per second). Compare this to the 42 million transistors
and the 2 GHz clock rate (i.e., 2,000,000,000 times per second) used in a Pentium 4. One of
Intel's 4004 chips still functions aboard the Pioneer 10 spacecraft, which is now the man-made
object farthest from the earth. Curiously, Busicom went bankrupt and never ended up using the
ground-breaking microprocessor.
Intel followed the 4004 with the 8008 and 8080. Intel priced the 8080 microprocessor at $360
dollars as an insult to IBM's famous 360 mainframe which cost millions of dollars.
 MITS Altair 8080 computer (1975):
The 8080 was employed in the MITS Altair computer, which was the world's first personal
computer (PC). It was personal all right: you had to build it yourself from a kit of parts that
arrived in the mail. This kit didn't even include an enclosure and that is the reason the unit shown
below doesn't match the picture on the magazine cover.
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 Cray 1 (1976):
It was the first commercial supercomputer. Supercomputer are state of the art machines designed
to perform calculations as fast as the current technology allows.
 Home user computers:
In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the
Macintosh. A Harvard freshman by the name of Bill Gates decided to drop out of college so he
could concentrate all his time writing programs for this computer. This early experienced put Bill
Gates in the right place at the right time once IBM decided to standardize on the Intel
microprocessors for their line of PCs in 1981. The Intel Pentium 4 used in today's PCs is still
compatible with the Intel 8088 used in IBM's first PC. 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.
Advantages:









Smaller in size as compared to previous generations
More reliable and less heat generation
Easly portable
Hardware failure is negligible
Much faster computational time (pico seconds)
Less power requirement
Totally general purpose
Manual labour required
Commercial production was easy and cheap
Limitations:

Highly sophisticated technology required for manufacturing the LSI chips
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. The use
of parallel processing and superconductors is helping to make artificial intelligence a reality.
Quantum computation and molecular and nanotechnology will radically change the face of
computers in years to come. The goal of fifth-generation computing is to develop devices that
respond to natural language input and are capable of learning and self-organization.
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Advantages:
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Much faster
More intelligent (reasoning, learning etc)
Massive primary memory capabilities
Hardware continued to shrink in size
Vocabulary within computers are increasing “talking machines” came in the market.
EXPLANATION:
Computers can perform complex and repetitive procedures quickly, precisely and reliably.
Modern computers are electronic and digital. The actual machinery (wires, transistors, and
circuits) is called hardware; the instructions and data are called software. All general-purpose
computers require the following hardware components:





Central processing unit (CPU): The heart of the computer, this is the component that
actually executes instructions organized in programs ("software") which tell the computer
what to do.
Memory (fast, expensive, short-term memory): Enables a computer to store, at least
temporarily, data, programs, and intermediate results.
Mass storage device (slower, cheaper, long-term memory): Allows a computer to
permanently retain large amounts of data and programs between jobs. Common mass
storage devices include disk drives and tape drives.
Input device: Usually a keyboard and mouse, the input device is the conduit through
which data and instructions enter a computer.
Output device: A display screen, printer, or other device that lets you see what the
computer has accomplished.
In addition to these components, many others make it possible for the basic components to work
together efficiently. For example, every computer requires a bus that transmits data from one part
of the computer to another.
CLASSIFICATION OF COMPUTERS:
I). Based on the operational principle of computers, they are categorized as analog, digital
and hybrid computers.
Operational Principle
A.
B.
C.
Analog
Digital
Hybrid
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Type of
computer
Digital
computer
Main frame
Computer
Micro
Computer
Home
Analog
computer
Super
Computer
Hybrid
Computer
Mini
Computer
PC
A. Analog Computers: These are almost extinct today. These are different from a digital
computer because an analog computer can perform
several mathematical operations simultaneously. It
uses continuous variables for mathematical operations
and utilizes mechanical or electrical energy. Analog
computer measures and answer the questions by the
method of “HOW MUCH”. The input data is not a
number infect a physical quantity like pressure, speed,
velocity. Other characteristics are;
 Signals are continuous of (0 to 10 V)
 Accuracy 1% Approximately
 High speed
 Output is continuous
 Time is wasted in transmission time
B. Digital Computers: They use digital circuits and are designed to operate on two states,
namely bits 0 and 1. They are analogous to states ON and OFF. Data on these computers
is represented as a series of 0s and 1s. Digital computers are suitable for complex
computation and have higher processing speeds. They are programmable. Digital
computers are either general purpose computers or special purpose ones. General purpose
computers, as their name suggests, are designed for specific types of data processing
while general purpose computers are meant for general use. Digital computer counts and
answer the questions by the method of “HOW Many”. The input data is represented by a
number. These are used for the logical and arithmetic operations. Logic is a science of
reasoning which tells that which statements will be followed next and the statement must
be true or false. There is no place for perhaps or if. Arithmetic means performing
mathematical operations on data, such as addition, subtraction, multiplication etc.
Other characteristics are;
 Signals are two level of (0 V or 5 V)
 Accuracy unlimited
 low speed sequential as well as parallel processing
 Output is continuous but obtain when computation is completed.
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C. Hybrid Computers: These computers are a combination of both digital and analog
computers. In this type of computers, the digital segments perform process control by
conversion of analog signals to digital ones. They are special purpose computers,
accurate like digital computers and fast like analog computers. They are used in hospitals,
spaceships, guided missiles etc.
Classification of digital computers:
Digital computes are classified on the basis of processing power into four sub-types, these are;
Processing Power
1.
2.
3.
4.
1.
Mainframe
Microcomputers
Minicomputers
Supercomputers
Mainframe Computers:
Mainframe computers are those computers that offer faster processing (100 millions
operation per second) and greater storage area. The word “main frame” comes from the
metal frames. It is also known as Father computer. Mainframe was a term originally
referring to the cabinet containing the central processor unit or "main frame" of a roomfilling Stone Age batch machine. After the emergence of smaller "minicomputer" designs
in the early 1970s, the traditional big iron machines were described as "mainframe
computers" and eventually just as mainframes. Nowadays a Mainframe is a very large
and expensive computer capable of supporting hundreds, or even thousands, of users
simultaneously.
The chief difference between a supercomputer and a mainframe is that a supercomputer
channels all its power into executing a few programs as fast as possible, whereas a
mainframe uses its power to execute many programs concurrently. In some ways,
mainframes are more powerful than supercomputers because they support more
simultaneous programs. But supercomputers can execute a single program faster than a
mainframe. The distinction between small mainframes and minicomputers is vague,
depending really on how the manufacturer wants to market its machines. Large
organizations use mainframes for highly critical applications such as bulk data processing
and ERP.
Most of the mainframe computers have capacities to host multiple operating systems and
operate as a number of virtual machines. They can substitute for several small servers.
Application – Host computer, Central data base server. They are also used by banks and
large companies. E.g IBM 4381, ICL 2900, NEC 610.
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2. Microcomputers (personal computers):
A computer with a microprocessor and its central processing unit is known as a
microcomputer. Micro computer are the smallest computer system. It can be defined as a
small, relatively inexpensive computer designed for an individual user. In price, personal
computers range anywhere from a few hundred pounds to over five thousand pounds. All
are based on the microprocessor technology that enables manufacturers to put an entire
CPU on one chip. Businesses use personal computers for word processing, accounting,
desktop publishing, and for running spreadsheet and database management applications.
At home, the most popular use for personal computers is for playing games and recently
for surfing the Internet. There size range from calculator to desktop size. Its CPU is
microprocessor. It also known as Grand child Computer. They do not occupy space as
much as mainframes do. When supplemented with a keyboard and a mouse,
microcomputers can be called personal computers. A monitor, a keyboard and other
similar input-output devices, computer memory in the form of RAM and a power supply
unit come packaged in a microcomputer. These computers can fit on desks or tables and
prove to be the best choice for single-user tasks. Application : - personal computer, Multi
user system, offices.
Microcomputers first appeared in the late 1970s. One of the first and most popular
personal computers was the Apple II, introduced in 1977 by Apple Computer. During the
late 1970s and early 1980s, new models and competing operating systems seemed to
appear daily. Today, the world of personal computers is basically divided between Apple
Macintoshes and PCs. The principal characteristics of personal computers are that they
are single-user systems and are based on microprocessors. However, although personal
computers are designed as single-user systems, it is common to link them together to
form a network. In terms of power, there is great variety. At the high end, the distinction
between personal computers and workstations has faded. High-end models of the
Macintosh and PC offer the same computing power and graphics capability as low-end
workstations by Sun Microsystems, Hewlett-Packard, and DEC.
Personal computers come in different forms such as desktops, laptops and personal
digital assistants. Let us look at each of these types of computers.
Personal Computers
a)
b)
c)
d)
e)
f)
g)
Desktop
Laptop
Netbook
PDA
Server
Wearable Computer
Tablet
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a) Desktops: A desktop is intended to be used on a single location. The spare parts of a
desktop computer are readily available at relatively lower costs. Power consumption is
not as critical as that in laptops. Desktops are widely popular for daily use in the
workplace and households. A computer designed to fit comfortably on top of a desk,
typically with the monitor sitting on top of the computer. Desktop model computers are
broad and low, whereas tower model computers are narrow and tall. Because of their
shape, desktop model computers are generally limited to three internal mass storage
devices. Desktop models designed to be very small are sometimes referred to as slimline
models.
b) Laptops: Similar in operation to desktops, laptop
computers are miniaturized and optimized for mobile
use. Laptops run on a single battery or an external
adapter that charges the computer batteries. They are
enabled with an inbuilt keyboard, touch pad acting as
a mouse and a liquid crystal display. The screen folds
down onto the keyboard when not in use. Their
portability and capacity to operate on battery power
have proven to be of great help to mobile users.
c) Netbooks: They fall in the category of laptops, but
are inexpensive and relatively smaller in size. They had a smaller feature set and lesser
capacities in comparison to regular laptops, at the time they came into the market. But
with passing time, netbooks too began featuring almost everything that notebooks had.
By the end of 2008, netbooks had begun to
overtake notebooks in terms of market share and
sales. An extremely lightweight personal
computer. Notebook computers typically weigh
less than 6 pounds and are small enough to fit
easily in a briefcase. Aside from size, the
principal difference between a notebook
computer and a personal computer is the display
screen. Notebook computers use a variety of
techniques, known as flat-panel technologies, to
produce a lightweight and non-bulky display
screen. The quality of notebook display screens varies considerably. In terms of
computing power, modern notebook computers are nearly equivalent to personal
computers. They have the same CPUs, memory capacity, and disk drives. However, all
this power in a small package is expensive. Notebook computers cost about twice as
much as equivalent regular-sized computers. Notebook computers come with battery
packs that enable you to run them without plugging them in. However, the batteries need
to be recharged every few hours.
d) Personal Digital Assistants (PDAs): PDA Short for personal digital assistant, a
handheld device that combines computing, telephone/fax, and networking features. A
typical PDA can function as a cellular phone, fax sender, and personal organizer. Unlike
portable computers, most PDAs are pen-based, using a stylus rather than a keyboard for
input. This means that they also incorporate handwriting recognition features. Some
PDAs can also react to voice input by using voice recognition technologies. The field of
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PDA was pioneered by Apple Computer, which introduced the Newton Message Pad in
1993. Shortly thereafter, several other manufacturers offered similar products. To date,
PDAs have had only modest success in the
marketplace, due to their high price tags and
limited applications. However, many experts
believe that PDAs will eventually become
common gadgets. PDAs are also called palmtops,
hand-held computers and pocket computers. It is
a handheld computer and popularly known as a
palmtop. It has a touch screen and a memory
card for storage of data. PDAs can also be used
as portable audio players, web browsers and
smart phones. Most of them can access the
Internet by means of Bluetooth or Wi-Fi
communication.
e) Servers: They are computers designed to provide services to client machines in a
computer network. They have larger storage capacities and powerful processors. Running
on them are programs that serve client requests and allocate resources like memory and
time to client machines. Usually they are very large in size, as they have large processors
and many hard drives. They are designed to be fail-safe and resistant to crash.
f) Wearable Computers: A record-setting step in the evolution of computers was the
creation of wearable computers. These computers can be worn on the body and are often
used in the study of behavior modeling and human health. Military and health
professionals have incorporated wearable computers into their daily routine, as a part of
such studies. When the users' hands and sensory organs are engaged in other activities,
wearable computers are of great help in tracking human actions. Wearable computers do
not have to be turned on and off and remain in operation without user intervention.
g) Tablet Computers: Tablets are mobile computers that are very handy to use. They have
the combine features of laptops and handhelds.
They use the touch screen technology. Tablets
come with an onscreen keyboard or use a stylus
or a digital pen. Apple's iPad redefined the
class of tablet computers. These were some of
the different types of computers used today.
Looking at the rate of advancement in
technology, we can definitely look forward to
many more types of computers in the near
future.
3. Minicomputers:
It is a midsize computer. In the past decade, the distinction between large minicomputers
and small mainframes has blurred, however, as has the distinction between small
minicomputers and workstations. But in general, a minicomputer is a multiprocessing
system capable of supporting from up to 200 users simultaneously. They are more
compact and less expensive. In terms of size and processing capacity, minicomputers lie
in between mainframes and microcomputers. Minicomputers are also called mid-range
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systems or workstations. The term began to be popularly used in the 1960s to refer to
relatively smaller third generation computers. They took up the space that would be
needed for a refrigerator or two and used
transistor and core memory technologies. The
12-bit PDP-8 minicomputer of the Digital
Equipment Corporation was the first successful
minicomputer. These are also small general
purpose system. They are generally more powerful
and most useful as compared to micro computer. It
behave like terminals at remote sites and data is
entered and sent to the mainframe which acts as
a host computer and hence distributed
processing is done. Mini computer are also known as mid range computer or Child computer.
Application :- Departmental systems, Network Servers, work group system. . E.g. PRIME
9755, IBM system 36.
4. Supercomputers: Supercomputer is a broad term for one of the fastest computers
currently available. Supercomputers are very expensive and are employed for specialized
applications that require immense amounts of mathematical calculations (number
crunching). For example, weather forecasting requires a supercomputer. Other uses of
supercomputers
scientific
simulations,
(animated)
graphics,
fluid
dynamic
calculations,
nuclear
energy
research,
electronic design, and analysis of geological
data (e.g. in petrochemical prospecting). They
can calculate at a rate of 400 million numbers
every second and are accurate upto 14 decimal
places. Perhaps the best known supercomputer
manufacturer is Cray Research. The highly
calculation-intensive tasks can be effectively
performed by means of supercomputers.
Quantum physics, mechanics, weather
forecasting, molecular theory are best studied
by means of supercomputers. Their ability of
parallel processing and their well-designed
memory hierarchy give the supercomputers,
large transaction processing powers.
Super computer are those computer which are designed for scientific job like whether
forecasting and artificial intelligence etc. They are fastest and expensive. A super
computer contains a number of CPU which operate in parallel to make it faster. It also
known as grand father computer. Application – whether forecasting, weapons research
and development. E.g. cray-1, CYBER 205.
THE END
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