ion characters tics of computer

8/6/2019 ion Characters Tics of Computer

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Definition of computer?

A machine for performing calculations automatically

A computer is a programmable machine that receives input, stores and

manipulates data, and provides output in a useful format.

Before electronic computers became commercially available, the term

"computer", in use from the mid 17th century, literally meant "one who

computes": a person performing mathematical calculations. ...

A programmable device that performs mathematical calculations and logicaloperations, especially one that can process, store and retrieve large amounts of

data very quickly; A person employed to perform computations.

An electronic machine that receives, processes and presents data. A computer can

be programmed to perform complicated tasks, like solving complex mathematical

equations or controlling a flight simulator. ...

Electronic machine capable of performing calculations and other manipulations ofvarious types of data, under the control of a stored set of instructions. The

machine itself is the hardware; the instructions are the program or software. ...

Technically, a computer is a programmable machine. This means it can execute aprogrammed list of instructions and respond to new instructions that it is given.

A computer is a device or machine for making calculations or controllingoperations that are expressible in numerical or logical terms. A computer can bemade to represent some aspect of a problem or part of a system. If a computer

configured in this way is given appropriate input data, then it can automatically

solve the problem or predict the behavior of the system.

Characterstics of a computer:

Speed: Computers work at very high speed and are much faster than humans. A second is

very large time period time for computer. A computer can perform billions of

calculations in a second. The time used by a computer to perform an operation is called

the processing speed. Computer speed is measured in Mega Hertz (MHz).

Storage: A computer can store a large amount of data permanently. User can use thisdata at any time. We can store any type of data in a computer. Text, graphic, pictures,

audio and video files can be stored easily. The storage capacity of the computer is

increasing rapidly.

Processing: (of Arithmetical and Logical Operations): A computer can process the given

instructions. It can perform different types of processing like addition, subtraction,multiplication and division. It can also perform logical functions like comparing two

numbers to decide which one is the bigger etc.

Accuracy: Accuracy means to provide results without any error. Computers can processlarge amount of data and generate error-free results. A modern computer performs

millions of operations in one second without any error.

Communication: Most computers today have the capability of communicating with

other computers. We can connect two or more computers by a communication device


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such as modem. These computers can share data, instructions, and information. Theconnected computer are called network.

Programmable-Devices: Controlled by set of instructions to do user specified tasks.

Retrieving data and programs:

The data and program stored on the storage media can be retrieved very quickly forfurther processing. It is also very important feature of a computer.

Automation:

A computer can automatically perform operations without interfering the user during the

operations. It controls automatically different devices attached with the computer. Itexecutes automatically the program instructions one by one.

Versatility

Versatile means flexible. Modern computer can perform different kind of tasks one by

one of simultaneously. It is the most important feature of computer. At one moment yourare playing game on computer, the next moment you are composing and sending emails

etc. In colleges and universities computers are use to deliver lectures to the students. The

talent of computer is dependent on the software.

Diligence

A computer can continually work for hours without creating any error. It does not get

tired while working after hours of work it performs the operations with the same accuracy

as well as speed as the first one.

No Feelings

Computer is an electronic machine. It has no feelings. It detects objects on the basis of

instructions given to it. Based on our feelings, taste, knowledge and experience: we can

make certain decisions and judgments in our daily life. On the other hand, computer cannot make such judgments on their own. Their judgments are totally based on instructions

given to them.

Consistency

People often have difficulty to repeat their instructions again and again. For example, alecturer feels difficulty to repeat a same lecture in a class room again and again.

Computer can repeat actions consistently (again and again) without loosing its

concentration:

To run a spell checker (built into a word processor) for checking spellings in adocument.

To play multimedia animations for training purposes.

To deliver a lecture through computer in a class room etc.

A computer will carry out the activity with the same way every time. You can listen a

lecture or perform any action again and again.

Precision

Computers are not only fast and consistent but they also perform operations veryaccurately and precisely. For example, in manual calculations and rounding fractional


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values (That is value with decimal point can change the actual result). In computerhowever, you can keep the accuracy and precision upto the level, you desire. The length

calculations remain always accurate.

Computer applications(examples)

The first electronic digital computers, with their large size and cost, mainly performedscientific calculations, often to support military objectives. The ENIAC was originally

designed to calculate ballistics firing tables for artillery, but it was also used to calculate

neutron cross-sectional densities to see if the hydrogen bomb would work properly. This

calculation, performed in December, 1945 through January, 1946 and involving over amillion punch cards of data, showed the design then under consideration would fail.

(Interestingly, many of the most powerful supercomputers available today are also used

for nuclear weapons simulations.) The CSIR Mk I, the first Australian stored-programcomputer, evaluated rainfall patterns for the catchment area of the Snowy Mountains

Scheme, a large hydroelectric generation project. Others were used in cryptanalysis, for

example the world's first programmable (though not general-purpose) digital electroniccomputer, Colossus, built during World War II. Despite this early focus of scientific

applications, computers were quickly used in other areas.

From the beginning, stored program computers were applied to business problems. The

LEO, a stored program-computer built by J. Lyons and Co. in Britain, was operationaland being used for inventory management and other purposes 3 years before IBM built

their first commercial stored-program computer. Continual reductions in the cost and size

of computers saw them adopted by ever-smaller organizations. And with the invention ofthe microprocessor in the 1970s, it became possible to produce inexpensive computers. In

the 1980s, personal computers became popular for many tasks, including book-keeping ,

writing and printing documents, calculating forecasts and other repetitive mathematical

tasks involving spreadsheets.

The Internet:

In the 1970s, computer engineers at various research institutions throughout the US

began to link their computers together using telecommunications technology. This effort

was funded by ARPA, and the computer network that it produced was called theARPANET (Advanced Research Projects Agency Network),. The technologies that made

the Arpanet possible rapidly spread and evolved. In time, the network spread beyond

academic institutions and became known as the Internet. In the 1990s, the developmentof World Wide Web technologies enabled ordinary, non-technical people to use the

internet, and it grew rapidly to become a global communications medium.

Advantages and disadvantages (generation of computers):

Computers can be divided into five generations depending upon the technologies used.

These are:

1. First Generation (1942 1955)

2. Second Generation (1955 1964)

3. Third Generation (1964 1975)

4. Fourth Generation (Since 1975)


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5. Fifth Generation (Since 1980)

1. First Generation Computers (1942 1955)

The vacuum tube technology was used in first-generation computers. Mark-1m, ENIAC,

EDSAC, EDVAC, UNIVAC-1 etc. machines belong to the first generation of computers.

The machine language only was used in first-generation computers.

Advantages

The main advantages of first-generation computers were:

1. These computers were the fastest of their time.

2. They were programmed using machine language.

3. The electronic digital computers were introduced due to the vacuum tubetechnology.

Disadvantages

The main disadvantages of first-generation computers were:

1. Very big in size2. Not reliable

3. Consumed large amount of energy

4. Constant maintenance required5. More heat generated and air-conditioning was required

6. More costly

7. Very slow in speed (data processing)

8. It was difficult to programmed, because they used only machine language9. Non-portable

10. Limited commercial use

2. Second Generation Computers (1955 1964)

The transistor technology was used in second-generation computers. The electroniccomponent transistor was invented in 1948 at Bell Laboratories. The transistor is smaller

in size and more reliable than vacuum tube. Therefore, the transistor technology was used

in computer in place of vacuum tube technology. The programming assembly languagewas also introduced in second-generation of computers.

Advantages

The main advantages of second-generation computers as compared to first-generation

computers are:

1. Low in cost2. Smaller in size

3. Fast in speed

4. Less heat generated More reliable and accurate in calculations5. Consume low power etc.

6. Used for commercial purposes

7. Portable


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8. Assembly language was introduced. This language is easy to write program thanmachine language

Disadvantages

The main disadvantages of this generation computers were:

1. Air-conditioning required2. Commercial production was difficult and these were very costly

3. Constant (or frequent) maintenance required

4. Only used for special purposes

3. Third Generation Computers (1964 1975)

The IC (Integrated Circuits) technology was used in third-generation computers. In a

small IC chip (5 mm square size) a circuit is designed having large number of electronic

components like transistors, capacitors, diodes, resistors etc. Initially, an IC containedonly about ten to twenty components. Thus the IC technology was named as Small Scale

Integration (SSI). The third-generation was based on IC technology and the computers

were designed using this technology.

Advantages

The main advantages of third-generation as compared to previous generations of

computers were:

1. Smaller in size

2. Production cost was low3. Very fast in computational power

4. More reliable

5. Low power consumption6. Maintenance cost was low because failure rate of hardware was very low

7. Magnetic disk, used for external storage

8. More storage capacity9. Easily portable

10. Easy to operate

11. Upgraded easily

12. Widely used for various commercial applications all over the world13. Lower heat generated

14. High-level languages were commonly used

15. Many input/output devices were introduced such as mouse and keyboard etc.

Disadvantages

The main disadvantages of third-generation computers were:

1. Air-conditioning required

2. Highly sophisticated technology required for the manufacturer chips


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4. Fourth Generation Computers (1975 onwards)

The microchip technology was introduced in this generation of computers. With the

advancement in IC technology, LSI (Large Scale Integration) chips were developed. It

was possible to itegrate over 30,000 or more components on to single LSI chip. AfterLSI, the VLSI (Very Large Scale Integration) was developed and the development of

microprocessor possible. It is expected that more than one million components will be

integrated on a single chip of VLSI. Using VLSI technology, the entire CPU is designed

on a single silicon chip. The use of microprocessor as CPU introduced another class ofcomputers called the microcomputers. Thus fourth-generation may be called

Microcomputer generation. IBM introduced its personal computer for use in 1981.

Advantages

The advantages of fourth-generation as compared to previous generation computers are:

1. Smaller in size

2. Production cost is very low

3. Very reliable4. Hardware failure is negligible

5. Easily portable because of their small size

6. Totally general purpose

7. Air conditioning is not compulsory8. Very high processing speed

9. Very large internal and external storage capacity

10. Used advanced input & output devices such as optical readers, laser printers, CD-ROM/DVD-ROM drives etc.

Disadvantages

The main disadvantages of fourth-generation computers is:

1. Highly sophisticated technology required for the manufacturer of microprocessorchips

5. Fifth Generation Computers (In process)

The main drawback of first to fourth generation computers is that the computers have not

their own thinking power. These are totally depending upon the instructions given by the

users.

Fifth generation computers are supposed to be the ideal computers, but do not exist. The

scientists are working to design such computers that will have the following features.

1. Having their own thinking power

2. Making decisions themselves3. Having capabilities of learning

4. Having capabilities of reasoning

5. Having large capacity of internal storage6. Having extra high processing speed


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7. Having capabilities of parallel processing

In these computers following technologies will be used:

ULSIC (Ultra Large Scale Integrated Circuits) technology

Artificial Intelligence (AI) technology also called the knowledge Processor. The

AI means automatic programs that let the machines to think and decidethemselves. The programming languages LISP (List Processor) and PROLOG

(Programming with Logic) are used for artificial intelligence. The scientists at

ICOT in Japan use the PROLOG to develop the Artificial Intelligence software.

Types of computers:

Computers can also be divided into three categories depending upon their instruction andform of input data that they accept and process. These are:

1. Analog Computers

2. Digital Computers

3. Hybrid Computers (analog + digital)

Differentiate between Analog and Digital Computers

ANALOG DIGITAL

1. Accept input data in continuousform and output is measured on a

scale.

2. It may have some errors in output.3. Have low internal memory.

4. Have fewer functions.

5. It is used only in scientific,industrial and medical fields.

6. It is costly.

7. It is not easily programmed.

1. Accept input data in digital form andoutput is received in digital form.

2. Output is accurate.

3. Have large internal memory.4. Have large number of functions.

5. It is general purpose in use.

6. It is low in cost.

7. It is easily programmed.

Classification of computers(four main groups.)

1. Supercomputer.

2. Mainframe computer.

3. Mini computer.

4. Microcomputer.

1. Supercomputer

Supercomputer is the most powerful and fastest, and also very expensive. It was

developed in 1980s. It is used to process large amount of data and to solve thecomplicated scientific problems. It can perform more than one trillions calculations per

second. It has large number of processors connected parallel. So parallel processing is


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done in this computer. In a single supercomputer thousands of users can be connected atthe same time and the supercomputer handles the work of each user separately. Super

computer are mainly used for:

Weather forecasting.

Nuclear energy research. Aircraft design.

Automotive design.

Online banking.

To control industrial units.

The supercomputers are used in large organizations, research laboratories, aerospace

centers, large industrial units etc. Nuclear scientists use supercomputers to create and

analyze models of nuclear fission and fusions, predicting the actions and reactions ofmillions of atoms as they interact. The examples of supercomputers are CRAY-1, CRAY-

2, Control Data CYBER 205 and ETA A-10 etc.

2. Mainframe Computers

Mainframe computers are also large-scale computers but supercomputers are larger thanmainframe. These are also very expensive. The mainframe computer specially requires a

very large clean room with air-conditioner. This makes it very expensive to buy and

operate. It can support a large number of various equipments. It also has multiple

processors. Large mainframe systems can handle the input and output requirements ofseveral thousand of users. For example, IBM, S/390 mainframe can support 50,000 users

simultaneously. The users often access then mainframe with terminals or personal

computers. There are basically two types of terminals used with mainframe systems.These are:

i) Dumb Terminal

Dumb terminal does not have its own CPU and storage devices. This type of terminaluses the CPU and storage devices of mainframe system. Typically, a dumb terminal

consists of monitor and a keyboard (or mouse).

ii) Intelligent Terminal

Intelligent terminal has its own processor and can perform some processing operations.Usually, this type of terminal does not have its own storage. Typically, personal

computers are used as intelligent terminals. A personal computer as an intelligent

terminal gives facility to access data and other services from mainframe system. It alsoenables to store and process data locally.

The mainframe computers are specially used as servers on the World Wide Web. Themainframe computers are used in large organizations such as Banks, Airlines and

Universities etc. where many people (users) need frequent access to the same data, whichis usually organized into one or more huge databases. IBM is the major manufacturer of

mainframe computers. The examples of mainframes are IBM S/390, Control Data

CYBER 176 and Amdahl 580 etc.


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3. Minicomputers

These are smaller in size, have lower processing speed and also have lower cost than

mainframe. These computers are known as minicomputers because of their small size as

compared to other computers at that time. The capabilities of a minicomputer are betweenmainframe and personal computer. These computers are also known as midrange

computers.

The minicomputers are used in business, education and many other government

departments. Although some minicomputers are designed for a single user but most aredesigned to handle multiple terminals. Minicomputers are commonly used as servers in

network environment and hundreds of personal computers can be connected to the

network with a minicomputer acting as server like mainframes, minicomputers are usedas web servers. Single user minicomputers are used for sophisticated design tasks.

The first minicomputer was introduced in the mid-1960s by Digital Equipment

Corporation (DEC). After this IBM Corporation (AS/400 computers) Data General

Corporation and Prime Computer also designed the mini computers.

4. Microcomputer

The microcomputers are also known as personal computers or simply PCs.

Microprocessor is used in this type of computer. These are very small in size and cost.

The IBMs first microcomputer was designed in 1981 and was named as IBM-PC. Afterthis many computer hardware companies copied the design of IBM-PC. The term PC-

compatible refers any personal computer based on the original IBM personal computer

design.

The most popular types of personal computers are the PC and the Apple. PC and PC-compatible computers have processors with different architectures than processors in

Apple computers. These two types of computers also use different operating systems. PC

and PC-compatible computers use the Windows operating system while Apple computersuse the Macintosh operating system (MacOS). The majority of microcomputers sold

today are part of IBM-compatible. However the Apple computer is neither an IBM nor a

compatible. It is another family of computers made by Apple computer.

Personal computers are available in two models. These are:

1. Desktop PCs2. Tower PCs

A desktop personal computer is most popular model of personal computer. The system

unit of the desktop personal computer can lie flat on the desk or table. In desktoppersonal computer, the monitor is usually placed on the system unit.

Another model of the personal computer is known as tower personal computer. The

system unit of the tower PC is vertically placed on the desk of table. Usually the system

unit of the tower model is placed on the floor to make desk space free and user can placeother devices such as printer, scanner etc. on the desktop. Today computer tables are

available which are specially designed for this purpose. The tower models are mostly

used at homes and offices.


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Microcomputer are further divided into following categories.

1. Laptop computer

2. Workstation

3. Network computer

4. Handheld computer

1. Laptop computer

Laptop computer is also known as notebook computer. It is small size (85-by-11 inch

notebook computer and can fit inside a briefcase. The laptop computer is operated on a

special battery and it does not have to be plugged in like desktop computer. The laptopcomputer is portable and fully functional microcomputer. It is mostly used during

journey. It can be used on your lap in an airplane. It is because it is referred to as laptop

computer.

The memory and storage capacity of laptop computer is almost equivalent to the PC ordesktop computer. It also has the hard dist, floppy disk drive, Zip disk drive, CD-ROM

drive, CD-writer etc. it has built-in keyboard and built-in trackball as pointing device.

Laptop computer is also available with the same processing speed as the most powerfulpersonal computer. It means that laptop computer has same features as personal

computer. Laptop computers are more expensive than desktop computers. Normally these

computers are frequently used in business travelers.

2. Workstations

Workstations are special single user computers having the same features as personal

computer but have the processing speed equivalent to minicomputer or mainframe

computer. A workstation computer can be fitted on a desktop. Scientists, engineers,

architects and graphic designers mostly use these computers.

Workstation computers are expensive and powerful computers. These have advanced

processors, more RAM and storage capacity than personal computers. These are usually

used as single-user applications but these are used as servers on computer network andweb servers as well.

3. Network computers

Network computers are also version of personal computers having less processing power,

memory and storage. These are specially designed as terminals for network environment.Some types of network computers have no storage. The network computers are designed

for network, Internet or Intranet for data entry or to access data on the network. The

network computers depend upon the networks server for data storage and to usesoftware. These computers also use the networks server to perform some processing

tasks.


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In the mid-1990s the concept of network computers became popular among some PCmanufacturers. As a result several variations of the network computers quickly became

available. In business, variations of the network computer are Windows terminals,

NetPCs and diskless workstations. Some network computers are designed to access onlythe Internet or to an Intranet. These devices are sometimes called Internet PCs, Internet

boxes etc. In home some network computers do not include monitor. These are connected

to home television, which serves as the output devices. A popular example of a home-based network computer is Web TV, which enables the user to connect a television to the

Internet. The Web TV has a special set-top box used to connect to the Internet and also

provides a set of simple controls which enable the user to navigate the Internet, send and

receive e-mails and to perform other tasks on the network while watching television.

Network computers are cheaper to purchase and to maintain than personal computers.

4. handheld computer

In the mid 1990s, many new types of small personal computing devices have been

introduced and these are referred to as handheld computers. These computers are also

referred to as Palmtop Computers. The handheld computers sometimes called Mini-Notebook Computers. The type of computer is named as handheld computer because it

can fit in one hand while you can operate it with the other hand. Because of its reduced

size, the screen of handheld computer is quite small. Similarly it also has small keyboard.The handheld computers are preferred by business traveler. Some handheld computers

have a specialized keyboard. These computers are used by mobile employees, such as

meter readers and parcel delivery people, whose jobs require them to move from place toplace.

The examples of handheld computers are:

1. Personal Digital Assistance

2. Cellular telephones

3. H/PC Pro devices

1. Personal Digital Assistance (PDAs)

The PDA is one of the more popular lightweight mobile devices in use today. A PDA

provides special functions such as taking notes, organizing telephone numbers and

addresses. Most PDAs also offer a variety of other application software such as wordprocessing, spreadsheet and games etc. Some PDAs include electronic books that enable

users to read a book on the PDAs screen.

Many PDAs are web-based and users can send/receive e-mails and access the Internet.

Similarly, some PDAs also provide telephone capabilities.

The primary input device of a PDA is the stylus. A stylus is an electronic pen and looks

like a small ballpoint pen. This input device is used to write notes and store in the PDA

by touching the screen. Some PDAs also support voice input.

2. Cellular phones


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Eductainment is another type of CBT. It is a type of educational software that combinesthe education with entertainment. These software are available on CD-ROMs and DVD-

ROMs and teach children in a fun and in exciting way. Similarly typein is learnt through

these types of software.

2. Entertainment

Computer has also played a very important role for the entertainment of humans.

Computer has become need of humans for entertainment at their home. Form example, to

play video games at home, different game software are available to play games.

Similarly, software are available to see movie films and to listen music. Today the moviefiles and famous songs are mostly available on CDs or on the web at very low cost. You

can listen music while you work on the computer.

On the web, you can view fine art images in online museums and galleries. Some artistssell their works online and others display them for your viewing pleasure.

3. E-Commerce

E-commerce (electronic commerce) of e-trade or e-business is a financial business

transaction conducted electronically between business partners over computer network

(such as on Internet). With e-commerce, transactions can occur instantaneously andglobally. This saves time for participants on both ends. The users can buy, sell and

exchange of products or services via computer network. Today, many mobile computers

can also access the internet on wireless.

There are many applications of e-commerce such as home banking, buying stocks,collaborating electronically with business partners around the globe, marketing and

advertising products, providing services to the customers etc.

There are several types of e-commerce like collaborative commerce business-to-

commerce, consumer-to-consumer, mobile commerce etc.

The following services are mostly used in e-commerce or e-business.

(i) E-Mail

It is the most popular service through which we can electronically send and receive

messages anywhere in the world. The spoken messages are sent and received throughvoice mail.

(ii) Video Conferencing

A video conference is a meeting between two or more people residing at various places.

They can watch and talk with each other. They use a network (i.e. Internet). Toparticipate in a video conference, you need a video camera, a microphone, speaker and

software (special video conferencing software). Video conferencing also need a computer

with a large memory and fast processor.

Video conferencing provides a complete simulation of a normal meeting environment,enabling both parties to see, hear and present material, just as if they are in the same

room.


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(iii) Electronic Shopping (E-Shopping)

Many businesses now have websites that allow internet users to buy goods or services.

Shopping can take place using a computer at home, or at a cybercafe. The e-shop can be

anywhere in the world and it remains open 24 hours a day. You can purchase any goodssuch as books, software, movies, computers, cars, airline tickets etc. on the web.

(iv) Electronic Banking

One of the most popular uses of e-commerce is electronic banking. An electronic banking

is also known as cyber-banking. It includes various banking activities conducted fromhome, a business, or on the road instead of a physical bank location. In all over the world,

about 95 percent banks are online.

4. Health Care

Nearly every area of the medical field uses computers, such as laboratories, researches,scanning, monitoring, pharmacy etc., which are helping the doctors to diagnose diseases

and many other purposes.

The main uses of computer in medical field are described below:

(i) Maintaining Patient History and Other Records

The complete bio-data as well as medical history of patient is recorded into the computerbefore check up of patient. The complete medical history (current and previous) is

delivered to the related doctor for the check up of patient. In this way, much of the

doctors time is saved.

In addition to patient history, other information about doctors, medicines, chemicals andequipments is also maintained. It is very easy and efficient way to organize records than

paper-based records. Any information about patients, doctors, equipments etc. can be

retrieved veryb easity and quickly. In hospitals, mostly all the medical wards areinterconnected through network. For example, if a patient is allocated a specific ward but

being examined by a consultant and receiving treatment in other areas (wards) of the

hospital, his detail can be viewed and updated at any terminal on the hospitals LANnetwork.

(ii) Patient Monitoring

The electronic scanning units (medical equipments) used in hospital can also be attached

to computers. These are very expensive and are used to monitor the patient continuously.Thus computers are normally used in the following medical units of hospitals.

ICU (Intensive Care Unit)

Operation Theater

Recovery Room Medical Ward

EGG (Electrocardiograph)

The medical equipment with sensors attached to the patient that detects changes of heart

rate, pulse rate, blood pressure, breathing and brain activity. If any unbalancing situationoccurs, computer activates the alarming device, which creates sound and alerts the


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medical staff. The data is also logged and used to analyze the change in a patientscondition over a period of time.

(iii) Diagnosis of Diseases

Computer is also used in hospital for diagnosis. For example, laboratory tests on blood

and tissue chemistry have become dependent on computer analysis.

One common use of computer is hospital is to scan the body of patient. A special scanner

is used for this purpose. A scanner sends electromagnetic rays through a patient body and

sensors detect that how much patients body have affected to any type of cancer (or

disease). For example, the CAT (Computerized Axial Topography) scanner passes raysover the patient. A CAT scanner takes many X-rays around the body. It displays an

image that enables physicians to look beneath the patients skin. As the scanner passes

over the patient, it displays and image of bone and tissue structure of patient on acomputer screen.

(iv) Telemedicine

Another improvement in the medical field is the telemedicne. In telemedicine, you can

access medical care centers using computers videoconferencing.

(v) Computer-Aided Surgery (CAS)

Many surgeons also use computer aided surgery while they are in training. It is used to

learn surgical techniques. The physicians and dentists also use the computer aided

learning (CAL) program.

Many websites also provide up-to-date medical, fitness, etc. information. These websites

also maintain databases about various problems and their solutions. There are also

medical chat rooms on the internet.

5. Science

Computer is used in all branches of science to collect and analyze data. The scientistsalso use internet to collect the latest information around the world. Today, it is impossible

to carry out scientific researches without use of computers. In all branches of science, it is

mainly used to get accurate experimental results, for example to get accurate forecastingof weather etc. Data analysis of Researches (in medical, pharmacy ,drug administration,

bio-informatics..etc)is done by computers.

6. Publishing

In the field of publishing, computer is playing very important role such as to publish thebooks, magazines and newspapers etc. The publishers use computer and word processors

and graphics software to design pages of the books or magazines. Many writes and

publishers use Internet to collect information that is used for compliling a new book ofmagazine. Some websites allow you to download and entire book, called an electronic

book (e-book). The journalists also use the notebook computers and digital cameras to

capture and record news.

7. Traveling


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Computer is also playing very important role in traveling by car or airplane to arriveeasily and safely at your destination. Today many vehicles manufactured use special

electronic equipments in the car that controls various activities of the car. These cars have

GPS (Global Positioning System) receiver that reports your vehicles location. These carsalso have Onboard Navigation Systems that have the following featuers.

Track the vehicle if it is stolen

Provide emergency services

Provide directions

Provide roadside assistance

Perform remote diagnostics if a warning light appears on the dashboard

To make hotel and restaurant reservations

Today many vehicles also include options such as screens with e-mail and internetaccess, printers, fax capability etc. Airlines also provide online access. The passengers

can connect their notebook or hand held computer to the web during their flights. Some

airlines also provide web surfing devices to their passenger during their flights.

Computer are also used in cars to monitor fluid levels, temperatures, electrical systemsetc. It is also used to monitor the air traffic etc.

8. Government

A government runs the country by making policies and provides citizens with up-to-date

information. Most of the government departments have their own websites. Thecomputers are used in all government departments have their own websites. The

computers are used in all government offices to perform various activities. The

government agencies use computers as part of their daily routine. Among other tasks, thefederal government uses computers to forecast the weather, to manage parks and

historical sites, to process immigrants, to produce social security checks and to collect

taxes. The most important use of the computer

9. Home

Like other electronic devices used in home such as T.V. set, washing machine etc.computer has also become the need of every person at home. It is used at home as an

educational tool for children. But it is also used at home to keep records, write letters,

prepare budgets, connect with others to send and get information on the internet, to watchfilms and to listen music or other entertainment etc.

10 Agriculture

In agriculture field also, computer is playing very important role. The agricultural

scientists are computer for analyzing the agricultural data. The students of agriculturealso uses computer to get latest information about agriculture on the internet. The farmers

also use computer to get information about crops and to calculate bills and cost per acre

as well as to get information about crops market prices.

11. Energy


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Energy companies use computers to locate or search oil, coal, natural gas and uranium.Similarly electric power companies use computers to monitor the power networks. In

addition, meter readers use hand held computers to record the units consumed in homes

and business.

12. Industry

In industry, computers are used to control the manufacturing system and continuous

running of the machinery. These also help in monitoring temperature [pressure, check the

quality and accuracy and measurement needed in the manufacturing process.

In industry, robots are used to perform most of the activities as mentioned above. A robotis an automatic programmable machine that moves and preforms mechanical tasks. It

means that a robot acts like human beings. Robot can work in environment that is

dangerous for human being such as opening chemical packages and packages believed tocontain bombs. It can perform repetitive tasks continuously without any break, at very

high accuracy than human. Robots can also be used in hundreds of applications such as:

Assembling & spray-painting cars

Lifting of heavy equipments, power cables etc.

Testing blood samples

Performing experiments in artificial satellites and radioactive environment etc.

13. Banking: - Before when there was no computer, every where manual system was

followed which was a very complicated and hard work but now with the coming ofcomputer every thing is in a very systematic way. Every bank is now using a

computerized system because it is very fast and user friendly. ATM cards are used every

where now which let us bank any time we want. PC banking (Personal Computerbanking) let us view our bank balance, request transfers between accounts and pay bills

electronically etc

14. Traffic light control: - In traffic light control the computer is being employed to drive

the traffic light. There are some programmed codes like " turn off the red light" or "turnon the red light" to control the traffic light and to carry out the instructions that follows.

Another most important application of computer in real life is:

15.Sports: - In sports computers are used wildly in conjunction with video cameras.

These are used to record the motion of all the sports men. 3D programs are used later on

to help the trainers see there movements and could improve there styles of playing.

16.Schools and Colleges: - Every student details need to be stored so a computer program

could help in this way. Multimedia, animations, graphics and charts could be used to

teach the students and many boring topics can be made interesting using multimedia.

Students could access internet for online help and courses for more information.

17. Businesses. Businessmen make bar graphs and pie charts from tedious figures to

convey information with far more impact than numbers alone can covey. Furthermore,computers help businesses to predict their future sales, profits, costs etc. making

companies more accurate in their accounts. Computers may also play a vital role in

aiding thousands of organizations to make judgmental and hard-provoking decisions

concerning financial problems and prospective trends.


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18. Buildings. Architects use computer animated graphics to experiment with possibleexteriors and to give clients a visual walk-through of their proposed buildings. The

computers provide architects a numerous amount of facilities to create different buildings

with greater accuracy, better designing and editing tools, and work done at the fastestspeed possible. Finally, a new kind of artist has emerged, one who uses computers to

express his or her creativity.

19. Law Enforcement. Recent innovation in computerised law enforcement include

national fingerprint files, a national file on the mode of operation of serial killers, andcomputer modeling of DNA, which can be used to match traces from an alleged

criminal's body, such as blood at a crime scene. In addition, computers also contain a

complete databases of all the names, pictures and information of such people who chooseto break the law.

20. Transportation. Computers are used in cars to monitor fluid levels, temperatures and

electrical systems. Computers are also used to help run rapid transit systems, load

containerships and track railroads cars across the country. An important part is the aircontrol traffic systems, where computers are used to control the flow of traffic between

airplanes which needs a lot of precision and accuracy to be dealt with.

21.Money. Computers speed up record keeping and allow banks to offer same-day

services and even do-it yourself banking over the phone and internet. Computers havehelped fuel the cashless economy, enabling the widespread use of credit cards, debit

cards and instantaneous credit checks by banks and retailers. There is also a level of

greater security when computers are involved in money transactions as there is a betterchance of detecting forged cheques and using credit/debit cards illegally etc.

22. Agriculture. Farmers use small computers to help with billing, crop information, and

cost per acre, feed combinations, and market price checks. Cattle ranchers can also use

computers for information about livestock breeding and performance.

23. Health and Medicine. Computers are helping immensely to monitor thee extremelyill in the intensive care unit and provide cross-sectional views of the body. This

eliminates the need for hired nurses to watch the patient twenty-four hours a day, which

is greatly tiring and error prone. Doctors use computers to assist them in diagnosingcertain diseases of the sort. This type of computer is called the Expert System, which is

basically a collection of accumulated expertise in a specific area of field. Computers are

now able to map, in exquisite detail, the structure of the human cold virus - the first steptowards the common cold. Furthermore, computers are used greatly in managing patients,

doctors, wards and medicine records, as well as deal with making appointments,

scheduling surgeries and other likes.

24. Manufacturing Industries. Computers have made their way towards jobs that wereunpleasant or too dangerous for humans to do, such as working hundreds of feet below

the earth or opening a package that might contain an explosive device. In other industries,

computers are used to control the production of resources very precisely. All robots andmachinery are now controlled by various computers, making the production process

faster and cheaper. All the stages of manufacturing, from designing to production, can be

done with the use of computer technology with greater diversity.


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25.The Human connection. The computers have evolved in such prosperity that it isnow able to assist or aid with humans who are disabled - both physically and mentally.

The handicapped are now able to express their missing sense with the aid of computer

technology. For example, a deaf and dumb person is able to communicate extensivelywith other people by using a specially designed computer system. This gives the disabled

a chance to live out life and gradually catch up with the other fortunate people living on

earth.

26. Scientific Research. This is very important for mankind and with the development ofcomputers; scientific research has propelled towards the better a great deal. Because of

high-speed characteristics of computer systems

27.Training. It is much more cheaper and effective to teach pilots how to fly in acomputerised cockpit or simulators, than is real airplanes. This is because the learning

pilots will feel much more relaxed and confident due to the fact that no life is at risk at

that moment. Railway engineers can also be given some kind of training on how to run a

train with the help of a computerised system. Training simulations are relatively cheaperand are always available on one-to-one basis making way for personal training.

28. Paperwork. Computer systems will increasingly cut down the paperwork that is

involved in millions of industries around the world. If a business is run on a manual

system, then the amount of papers or registers involved is a great deal, making theadministration process more tedious and error prone. If it is replaced by a computer

system, then all the necessary data and information is transferred into the memory of the

computer. This makes managing various tasks easier, faster and more effective than themanual system. Organisations that involve administrative tasks such as a hotel, school,

hospitals, clubs, libraries etc. will become more efficient if a computer system is

implemented.

29. Real Time systems. Many computers provide an environment, which is completelybased on real time. This means processing of one entity is done so quickly and

effectively, that another entity is not effected. For example Airline systems and Banking

systems will come under this category. These systems are immensely huge because theyinteract with all other airlines or banking systems in the world. A computer system,

therefore, becomes more than just necessary in daily uses.

The basic functions of computer:

The original function of the personal computer was to help the End-User to do Basic

Accountant Processing, and or Book Keeping for the busy Home Person that wasnormally employed with the proper finances.you can do with it like on line educationalthings and or play video game for entertainment or begin to learn more of what you can if

you are just starting out with them.

Other computer functions are:

To run user application programs


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to do repetitive tasks or compute mathematical equations very fast (to compute amandlebrot set by hand it would take 3yrs, with a computer it would take a

fraction of a second).

to convey store and manage information.

to accomplish automated tasks; trivial (flipping traffic lights back and forth) or

advanced (integrating a calculus function).

Before learning how to use a computer, you must first learn the different functionsthat a computer can perform. Basically, there are four functions, input, output,

storage, processing.

Functional composition of a digital computer: (Diagram1)

Basic four function of computers are:

Input

Computer can keep track of any different types of information. With software like

microsoft word, notepad. it makes inputing any data such as words, articles relatively

easy. Examples of input devices include, your keyboard, computer mouse, microphoneetc.

Processing

Computer can rapidly solve all types of numerical problems. Solving numerical problems

can be considered as an example of computer processing. With the ability of datamanipulation of company, task can be completed efficiently with effectively. Saving lots

and lots of time and effort, compared to human work. Also, computer are accurate and


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It is the backbone of the computer, designed to transferinformation and power to and from all of the major components.

Other components are usually plugged into this device, and it is

almost always the largest board in the computer. Also called a"Mainboard" or "mobo". The motherboard contain the BIOS

(Basic Input/Output System) that allows all the components to

communicate with each other.

1. Microprocessor - This is the brain of your computer. It performscommands and instructions and controls the operation of the

computer.

2. Memory - The RAM in your system is mounted on themotherboard. This is memory that must be powered on to retain its

contents.

3. Drive controllers - The drive controllers control the interface of

your system to your hard drives. The controllers let your harddrives work by controlling their operation. On most systems, they

are included on the motherboard, however you may add additional

controllers for faster or other types of drives.

3. Hard disk drive(s) - This is where your files are permanently stored on

your computer. Also, normally, your operating system is installed here.

4. CD-ROM drive(s) - This is normally a read only drive where files are

permanently stored. There are now read/write CD-ROM drives that use

special software to allow users to read from and write to these drives.

5. Floppy drive(s) - A floppy is a small disk storage device that todaytypically has about 1.4 Megabytes of memory capacity.

6. Other possible file storage devices include DVD devices, Tape backupdevices, and some others.

2. Monitor - This device which operates like a TV set lets the user see how the

computer is responding to their commands.

3. Keyboard - This is where the user enters text commands into the computer.

4. Mouse - A point and click interface for entering commands which works well ingraphical environments.


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Accessories and Peripherals include:

Optical Devices - It has become common for a computer to contain CD-ROM, DVD-

ROM, BLU-RAY ROM or writing devices of the aforementioned types.

LAN CARD - Known officially as a Network Interface Card (NIC), these devices

connect a computer to a network, usually to a router or modem which establishes

connectivity to the Internet. These are usually PCI expansion cards or built into amotherboard and output in RJ-45 format. The cable tips (RJ-45) look similar to a phone

cable (RJ-11), but are larger. They are commonly called Ethernet Cables.

USB ports - /printers/flashdrives.

Various Diagrams with Components and peripherals:

(a)

(B)Computer Components(Anatomy):

Computer components are the parts of the computer which are collectively used to offersmooth, fast and accurate operating. Each and every component has a significant feature

which makes your computer work better. The basic components are the computer case,

CPU, power supply, hard drive, disk drive, video cards, mouse, monitor and many more.The most popularly and readily available in the market and online stores are Frontech

external miracle TV box,8 port VGA video splitter, All in one card reader, Crimping


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Hard Disk Drives Disk drive is the mechanism to run the disks. All disks need a driveto get the information, read it and put it back to the disks. Hard disk is used to store the

data permanently. Often the terms disk and drive used to describe the same thing but it

should be clear that a disk is a storage device.

Modem A modem is used for the modulation and demodulation of the data that istransferred through the modem and the telephone lines. Modem translates the data from

digital to analog from analog to digital. Because on the telephone lines data can travel in

the form of the analog signals and in the computer data transmits in the form of digitalsignals. Modems are measured by the speed which is called baud rate. The typical baud

rate is 56Kb.

Keyboard The keyboard is used to type something or input information to the

computer. There are different designs and models of the keyboards in the market. Themost common layout of the keyboard is QWERTY layout. A standard keyboard has 101

keys and embedded keys.

Video cards-Video cards allow computer to display video, graphics and animation. Some

video cards allow computers to display television. A video card with a digital videocamera allows users to produce live video. A high speed broadband internet connection is

required to watch the videos on net.

Network cards:Network interface cards allow PCs to connect with each other and

communicate. Every network computer is required to have a NIC card. NIC cards arerequired both in wired and wireless networking.

Cables: There are two broad types of cables internal cables, which are embedded on the

mother board circuit that performs the communication between the devices and CPU. Theother types of the cables are the network cables like coaxial cable, CAT 5, Ethernet

cables. These cables are used for the communication purposes between the devices or

computers.

Memory Memory is the one of the important piece of the hardware. Sometimesmemory chip memory is confused with the hard disk memory. Sometimes unallocated

space of the hard disk is used as virtual memory also known as page file. This type of

memory is a temporary memory and is used actual memory is less and requires some

additional memory to perform a specific task.

RAM (Random Access Memory) RAM is a memory that is being used by the computer

to store the information temporarily. For example when some work is performed on some

applications that work is temporarily stored in the RAM. More RAM in the computermore faster computer works. Today at least requirement of a modern PC is 64 RAM.

RAM is in the form of a chip and different vendors have developed the RAM of differentcapacities.

Mouse Every modern computer requires a mouse for faster operations. Generally amouse has two buttons left and right to perform different functions. One type of the

mouse has a round ball under the bottom. Another type of the mouse use optical system

to track the movement of the mouse.


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Monitors The monitor is used to display the information on the screen. All theactivities of a computer, functions and tasks are seen on the computer screen and this is

called outputting information. Monitors come in many sizes and shapes, monochrome or

full colors. Today most computers use LCD screens. It is light weight and consumes lesspower as compared to the monitors.

Printers The printer takes the information from the PC and transfers it to the paper of

different sizes, which are placed in the printer device. There are three basic types of a

printer such as dot matrix, inkjet and laser.

Scanners- Scanners allow you to transfer pictures and photographs to your computer. Ascanner is used to scan the images and pictures. You can then send the image to someone,

modify it or take a print out of it. With optical character recognition software you can

convert printed documents into the text that you can use in the word processor.Digital camera- You can take the digital photographs with the digital cameras. The

images are stored on the memory chip of the digital cameras and you can transfer them to

your computer with the USB drive.

Case Case or casing covers the whole computers circuitry. There are two types ofcasings desktop and tower casing. There is room inside the casing to add or remove

components. Cases come in many sizes like desktop, mini, midi and tower. There are

some additional empty slots inside the cases such as IDE, USB, ASI, PCI and firewireslots.

Cards Cards are the hardware components that are added to the computer to increase

their functionalities and capabilities.

Sound cards produce the sound like music and voice. The older cars were 8, 16 and then32 bits.

Color cards allow computers to produce colors. Initially there were 2, 4 and then 16 bits.

The main types of the graphic cards are EGA, VGA and SGA. The 32 cards are the

standard to display almost billions of the colors on the monitor.

Moors-Law :


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Binary Coded Decimal

To the right we have provided a table of

BCD data which is all based upon the old"1's" and "0's".

If at first it looks a bit intimidating don't

worry you will very quickly get the hang

of it. Notice first of all we have in theextreme right hand column the numbers 0

- 9 and the letters A to F. The first four

columns are headed 8 - 4 -2 - 1

We explained earlier by adding switchesyou double the previous capacity for

numbering in binary. Notice the pattern

of our 0's and 1's. Under the column 1 weget a succession of 0, 1, 0, 1..... Under

the column 2 we get a succession of 0, 0,

1, 1..... etc.

In fact under every column heading youhave exactly an equal number of zeros

first followed by the same number of

ones. Look at column 8 for example.Eight zeros followed by eight ones.

Now look at the far right column and

look up number seven, follow that row

reading across right to left and you will

see the sequence 0 - 1 - 1 - 1. Okay if aone means a turned on switch with the

value of that column what does 4 + 2 + 1=?

Binary Coded Decimal -BCD

8 4 2 1 0 0 0 0 0

0 0 0 1 1

0 0 1 0 2

0 0 1 1 30 1 0 0 4

0 1 0 1 5

0 1 1 0 6

0 1 1 1 7

1 0 0 0 8

1 0 0 1 9

1 0 1 0 A

1 0 1 1 B

1 1 0 0 C

1 1 0 1 D

1 1 1 0 E

1 1 1 1 F

Of course the answer was seven. Try it with any number you like. Alright what's this A to

F stuff? Look at a digit on a digital clock or watch for example. For those numbers to be

represented in digital format requires four switches but now we will start using thecorrect terms. The word is "bits", heard that before? Now we're right into digital basics.

Four bits are called "a nibble" and guess what?, eight bits are called "a byte". Bet you've

heard that one for sure unless you live under a rock.

You should know by now that four switches (OK bits right!) can represent sixteen states

and with a digital clock you only go 0 to 9 and don't need anything else so that was calledBCD or Binary Coded Decimal. The last word is because we humans count in decimal

format or decades. Digital devices including computers DON'T, they can't. All they see

are ones and zeros, nothing else.


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Digital Basics of Computers:

Early computer programmers needed the digital basics to some way represent the human

recognised numbers 10 to 15 under the decimal system in a way which still represented

one decade. They conveniently chose A - F the first six letters of the alphabet and six inlatin is "HEX". Hex-Decimal was born, six alphabetical characters with ten decimal

numbers comprising a set of sixteen unique settings of bits all told. The first homecomputers such as my old personal favourite, the Apple II, had an eight bit "data bus"which dealt in "bytes" and had a sixteen bit (65,536 or 64K) "address bus".

The only changes since the 1970's has been the ever increasing speed of the digital logic

blocks contained within microprocessors, repeated doubling of the number of switches,

(er sorry bits!) reduced power consumption for efficiency, and expanded on board"instruction sets" of micro-code for sharp programmers to use. Dead simple really.

By the way, computers and other digital devices can NOT multiply or divide, they can

only add and subtract or shift a sequence of bits left or right. When a computer ostensibly

multiplies 3 X 4 it actually deep down in the nitty gritty department of all those basiclogic blocks shown in figure 3 above, which are buried deep within your IBM or Mac

microprocessor, takes the number four, adds four again and; finally adds four again to get

twelve. Anyone who tells you otherwise reveals a deep ignorance of digital basics, trustme.

Want more proof? Take the word "proof". In ASCII format the word "proof" in lower

case is five letters of the alphabet represented as a sequence of hex-decimal bytes as

follows -

70 72 6F 6F 66

in decimal format that would be

112 114 111 111 102

A computer looks at those sequence of bytes to "interpret" the word "proof". To achieve

that colour change to red I used the html instruction which of

course is a six byte instruction in hex-decimal. As an exercise for yourself see if you cansee how the conversion from hex-decimal to decimal equivalent for the word "proof"

occurs. O.K. it's just digital basics.

Basics of digital computer hardwareA computer is a programmable machine (or more precisely, a programmable sequential state

machine). There are two basic kinds of computers: analog and digital.

Analog computers are analog devices. That is, they have continuous states rather than

discrete numbered states. An analog computer can represent fractional or irrational values


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exactly, with no round-off. Analog computers are almost never used outside ofexperimental settings.

A digital computer is a programmable clocked sequential state machine. A digital

computer uses discrete states. A binary digital computer uses two discrete states, such as

positive/negative, high/low, on/off, used to represent the binary digits zero and one.

The French word ordinateur, meaning that which puts things in order, is a good

description of the most common functionality of computers.

what are computers used for?

Computers are used for a wide variety of purposes.

Data processing is commercial and financial work. This includes such things asbilling, shipping and receiving, inventory control, and similar business related functions,

as well as the electronic office.

Scientific processing is using a computer to support science. This can be as simple as

gathering and analyzing raw data and as complex as modelling natural phenomenon(weather and climate models, thermodynamics, nuclear engineering, etc.).

Multimedia includes content creation (composing music, performing music,

recording music, editing film and video, special effects, animation, illustration, laying outprint materials, etc.) and multimedia playback (games, DVDs, instructional materials,

etc.).

parts of a digital computer

The classic crude oversimplication of a computer is that it contains three elements:processor unit, memory, and I/O (input/output). The borders between those three terms

are highly ambigious, non-contiguous, and erratically shifting.


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A slightly less crude oversimplification divides a computer into five elements:

arithmetic and logic subsystem, control subsystem, main storage, input subsystem, andoutput subsystem.

processor

The processor is the part of the computer that actually does the computations. This is

sometimes called an MPU (for main processor unit) orCPU (for central processing unitor central processor unit).

A processor typically contains an arithmetic/logic unit (ALU), control unit (including

processor flags, flag register, or status register), internal buses, and sometimes special

function units (the most common special function unit being a floating point unit forfloating point arithmetic).

Some computers have more than one processor. This is called multi-processing.

The major kinds of digital processors are: CISC, RISC, DSP, and hybrid.

CISC stands for Complex Instruction Set Computer. Mainframe computers and

minicomputers were CISC processors, with manufacturers competing to offer the mostuseful instruction sets. Many of the first two generations of microprocessors were also

CISC.

RISC stands for Reduced Instruction Set Computer. RISC came about as a result of

academic research that showed that a small well designed instruction set runningcompiled programs at high speed could perform more computing work than a CISC

running the same programs (although very expensive hand optimized assembly language

favored CISC).


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DSP stands for Digital Signal Processing. DSP is used primarily in dedicated devices,such as MODEMs, digital cameras, graphics cards, and other specialty devices.

Hybrid processors combine elements of two or three of the major classes of

processors.

Arithmetic and logic

An arithmetic/logic unit (ALU) performs integer arithmetic and logic operations. Italso performs shift and rotate operations and other specialized operations. Usuallyfloating point arithmetic is performed by a dedicated floating point unit (FPU), which

may be implemented as a co-processor.

control

Control units are in charge of the computer. Control units fetch and decode machineinstructions. Control units may also control some external devices.

A bus is a set (group) of parallel lines that information (data, addresses, instructions,

and other information) travels on inside a computer. Information travels on buses as a

series of electrical pulses, each pulse representing a one bit or a zero bit (there are trinary,or three-state, buses, but they are rare). An internal bus is a bus inside the processor,

moving data, addresses, instructions, and other information between registers and other

internal components or units. An external bus is a bus outside of the processor (butinside the computer), moving data, addresses, and other information between major

components (including cards) inside the computer. Some common kinds of buses are the

system bus, a data bus, an address bus, a cache bus, a memory bus, and an I/O bus.

main storage

Main storage is also called memory or internal memory (to distinguish from external

memory, such as hard drives).

RAM is Random Access Memory, and is the basic kind of internal memory. RAM is

called random access because the processor or computer can access any location inmemory (as contrasted with sequential access devices, which must be accessed in order).

RAM has been made from reed relays, transistors, integrated circuits, magnetic core, or

anything that can hold and store binary values (one/zero, plus/minus, open/close,positive/negative, high/low, etc.). Most modern RAM is made from integrated circuits. At

one time the most common kind of memory in mainframes was magnetic core, so many

older programmers will refer to main memory as core memory even when the RAM is

made from more modern technology. Static RAM is called static because it will continueto hold and store information even when power is removed. Magnetic core and reed

relays are examples of static memory. Dynamic RAM is called dynamic because it loses

all data when power is removed. Transistors and integrated circuits are examples of


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dynamic memory. It is possible to have battery back up for devices that are normallydynamic to turn them into static memory.

ROM is Read Only Memory (it is also random access, but only for reads). ROM is

typically used to store thigns that will never change for the life of the computer, such as

low level portions of an operating system. Some processors (or variations withinprocessor families) might have RAM and/or ROM built into the same chip as the

processor (normally used for processors used in standalone devices, such as arcade video

games, ATMs, microwave ovens, car ignition systems, etc.). EPROM is ErasableProgrammable Read Only Memory, a special kind of ROM that can be erased and

reprogrammed with specialized equipment (but not by the processor it is connected to).

EPROMs allow makers of industrial devices (and other similar equipment) to have thebenefits of ROM, yet also allow for updating or upgrading the software without having to

buy new ROM and throw out the old (the EPROMs are collected, erased and rewritten

centrally, then placed back into the machines).

Registers and flags are a special kind of memory that exists inside a processor.Typically a processor will have several internal registers that are much faster than main

memory. These registers usually have specialized capabilities for arithmetic, logic, and

other operations. Registers are usually fairly small (8, 16, 32, or 64 bits for integer data,address, and control registers; 32, 64, 96, or 128 bits for floating point registers). Some

processors separate integer data and address registers, while other processors have

general purpose registers that can be used for both data and address purposes. A

processor will typically have one to 32 data or general purpose registers (processors withseparate data and address registers typically split the register set in half). Many

processors have special floating point registers (and some processors have general

purpose registers that can be used for either integer or floating point arithmetic). Flags aresingle bit memory used for testing, comparison, and conditional operations (especially

conditional branching).

external storage External storage (also called auxillary storage) is any storage other than mainmemory. In modern times this is mostly hard drives and removeable media (such as

floppy disks, Zip disks, optical media, etc.). With the advent of USB and FireWire hard

drives, the line between permanent hard drives and removeable media is blurred. Otherkinds of external storage include tape drives, drum drives, paper tape, and punched cards.

Random access or indexed access devices (such as hard drives, removeable media, and

drum drives) provide an extension of memory (although usually accessed through logicalfile systems). Sequential access devices (such as tape drives, paper tape punch/readers, or

dumb terminals) provide for off-line storage of large amounts of information (or back ups

of data) and are often called I/O devices (for input/output).

input/output overview

Most external devices are capable of both input and output (I/O). Some devices are

inherently input-only (also called read-only) or inherently output-only (also called write-

only). Regardless of whether a device is I/O, read-only, or write-only, external devices

can be classified as block or character devices.


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A character device is one that inputs or outputs data in a stream of characters, bytes,or bits. Character devices can further be classified as serial or parallel. Examples of

character devices include printers, keyboards, and mice.

A serial device streams data as a series of bits, moving data one bit at a time.

Examples of serial devices include printers and MODEMs.

A parallel device streams data in a small group of bits simultaneously. Usually the

group is a single eight-bit byte (or possibly seven or nine bits, with the possibility of

various control or parity bits included in the data stream). Each group usually

corresponds to a single character of data. Rarely there will be a larger group of bits(word, longword, doubleword, etc.). The most common parallel device is a printer

(although most modern printers have both a serial and a parallel connection, allowing

greater connection flexibility).

A blockdevice moves large blocks of data at once. This may be physically

implemented as a serial or parallel stream of data, but the entire block gets transferred as

single packet of data. Most block devices are random access (that is, information can be

read or written from blocks anywhere on the device). Examples of random access blockdevices include hard disks, floppy disks, and drum drives. Examples of sequential access

block devcies include magnetic tape drives and high speed paper tape readers.

input

Input devices are devices that bring information into a computer.

Pure input devices include such things as punched card readers, paper tape readers,

keyboards, mice, drawing tablets, touchpads, trackballs, and game controllers.

Devices that have an input component include magnetic tape drives, touchscreens, and

dumb terminals.

output

Output devices are devices that bring information out of a computer.

Pure output devices include such things as card punches, paper tape punches, LED

displays (for light emitting diodes), monitors, printers, and pen plotters.

Devices that have an output component include magnetic tape drives, combinationpaper tape reader/punches, teletypes, and dumb terminals.

ion characters tics of computer

Documents