Computer xi

ByBy

Mrs. Niti AroraMrs. Niti Arora

IndexIndex Computer OverviewComputer Overview Computer MemoryComputer Memory Input DevicesInput Devices Output DevicesOutput Devices ExitExit

Computer System : An OverviewComputer System : An Overview

“Information is power and Computers are amplifiers of information”

Computer is an electronic device that stores, retrieves, and processes data, and can be programmed with instructions. A computer is composed of hardware and software, and can exist in a variety of sizes and configurations.

Computer has evolved an information technology era which refers to the Creation, Gathering, Processing, Storage, Presentation and Dissemination of information.

COMPUTER AND INFORMATION

Information is a powerful tool and is the driving force behind every economy.

In today’s world , Information is multiplying at a manifold speed, and to manage it we need the help of a magic machine - The Computer.

COMPUTER AND INFORMATION

Information is a powerful tool and is the driving force behind every economy.

In today’s world , Information is multiplying at a manifold speed, and to manage it we need the help of a magic machine - The Computer.

SPEED It has an ability to perform at a high speed. The human equivalent of an average computer would be more than one million mathematicians working 24 hours a day.

ACCURACY Computers are very accurate. If the input and the instructions are accurate the output will also be accurate.

RELIABILTY Computer are immune to tiredness and boredom or fatigue. They are more reliable than human being.

HIGH STORAGE CAPACITY Computer has a very large memory to store data.

DILIGENT Unlike humans Computer does not get bored or tired. Hence can work for long hours.

VERSATILITY Computer can perform various jobs efficiently. It can work in various areas.

Weakness of computer

HIGH STORAGE CAPACITY Computer has a very large memory to store data.

DILIGENT Unlike humans Computer does not get bored or tired. Hence can work for long hours.

VERSATILITY Computer cn perform various jobs efficiently. It can work in various areas.

Where all this magic machine can be used ?

Field Of Education Computers are used as a teaching aid and as a research tool.

Medical field

Railways and Airways ticket reservation.

Banking and accounts

Communications - E-mail, Video conferencing banking and brokerage etc.

Weather forecast

Space research

Design and research work

Law enforcement by Police

Government

Military

Music

Theatre, film And Television

Computer at Home

.  The first home personal computer was not sold until 1977.  We have come a long way since then.  Did you know that in 1983 there were approximately 2 million personal computers in use in the United States alone.  However just 10 years later in 1993 the number had jumped to more than 90 million.

Inside View of the Computer

Floppy Drive

RAM

ROM

SPEAKER

HARD DISK DRIVE

How A Computer Works!

INPUT PROCESSINGDATA

OUTPUTINFORMATION

• We feed the Data through Input unit (Keyboard)

• Computer Processes (Works on) the data in the Processing unit - CPU

• Computer gives the information (Result)

•Data- Unprocessed raw facts and figures are known as DATA.

•Information- processed data which conveys proper meaning is known as INFORMATION.

•Personal Computer- A compact machine which can be placed on a table used for daily day-today work used in offices, school etc. is called PERSONAL COMPUTER.

Types of computer

Embedded Computer. Computer which exist in various size used in various appliances.

Programmable Computer. Computer which comes in various sizes, speed etc.

Laptop & Desktop. Computer used in home and business etc.

Workstation. Computer used for connecting other computer in a computer network.

Main frames. Computer used for sharing ,controlling inter connected computer.

Super computer. Computer used in complex time consuming calculation

The Central Processing Unit(CPU) of a computer is responsible for carrying out the processing job with aid of memory. The CPU is the brain of computer.

Components of CPU:-

•Arithmetic Logic Unit(ALU)

•Control UNIT(CU)

•Memory

The ALU is responsible for carrying out arithmetic operations such as addition and subtraction as well as logical decisions such as whether one number is bigger than another. All programs consist of complex sets of arithmetic and logical operations. Another way of thinking of a logical operation is as a decision making operation.

The control unit is responsible for loading and interpreting the individual instructions that comprise the computer program. These instructions are in a language called machine code. Machine code is a pattern of ones and zeros. The control unit also has the task of getting the data needed by the instructions and returning the results of the processing after the instruction has been executed.

Because the CPU can perform its operations much faster than data can be transferred from RAM, many CPUs have on-board cache memory. This is memory that the control unit can access very quickly and use for intermediate storage. Further, data and instructions can be loaded into cache before they are actually needed. When they are needed, the transfer is much faster than it would have been if RAM had been used.

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Computer MemoryComputer MemoryComputer MemoryComputer Memory

Concept of MemoryConcept of MemoryConcept of MemoryConcept of MemoryLet’s understand what is Computer’s Let’s understand what is Computer’s

memory ...memory ...

It is an electronic holding place It is an electronic holding place for the instructions and the data for the instructions and the data that the microprocessor of the that the microprocessor of the

computer can reach quickly. Like computer can reach quickly. Like the Grey cells in our brain, the the Grey cells in our brain, the computer memory consists of computer memory consists of

binary cells to store the binary cells to store the information.information.

CComputeromputer memory is measured in bytes.  A memory is measured in bytes.  A single byte is made up of a series of single byte is made up of a series of 1's1's and and 0's0's normally traveling in pairs of eight.  These normally traveling in pairs of eight.  These eight 0's and 1's are the way the computer eight 0's and 1's are the way the computer communicates and stores information.  With communicates and stores information.  With each keystroke or character a each keystroke or character a bytebyte of memory of memory is used.  In another article you will learn more is used.  In another article you will learn more about bits and how the computer thinks.about bits and how the computer thinks.

Measuring Memory

Term/Byte Abbreviation Value

Kilo K, KB 1,024 bytes

Mega M, MB, Meg 1,048,576 bytes (Million)

Giga G, GB, Giga1,073,741,824 bytes (Billion)

Tera T, TB, Tera1,099,511,628,000 bytes (Trillion)

8 bits = 1 byte

1000 bytes = 1 kilobyte

1000 kilobytes = 1 megabyte

1000 megabytes = 1 gigabyte

1000 gigabytes = 1 terabyte

Here is another way of looking at the measurement of memory:

Measuring Bytes

Types of MemoryTypes of Memory

P rim a ry S e con d a ry

M e m o ry

Primary MemoryPrimary Memory

Primary memoryPrimary memory is the memory that is intimately is the memory that is intimately

associated with the actual working of the associated with the actual working of the computer. This includes memory that holds the computer. This includes memory that holds the start-up routines as well as the current program start-up routines as well as the current program and data it is working with. There are various and data it is working with. There are various forms of primary memory: RAM, ROM and Cache forms of primary memory: RAM, ROM and Cache memory. memory. It is the main or internal memory . It is the main or internal memory .

It can be broadly categorized into It can be broadly categorized into two partstwo parts

RAMRAM (Random Access Memory) (Random Access Memory)

ROMROM (Read Only Memory) (Read Only Memory)

CacheCache

Primary MemoryPrimary Memory

RAMRAM

It is known as the It is known as the Read and Write Read and Write memorymemory.This memory is .This memory is volatile.volatile.

Whatever information you store is Whatever information you store is temporary in nature and when you temporary in nature and when you switch off the computer everything is switch off the computer everything is erased.erased.

ROMROMROMROM

It is a memory unit that It is a memory unit that performs theperforms the Read operationRead operation only and only and does not does not have a write capabilityhave a write capability. .

The Binary information in the The Binary information in the ROMROM is is made permanent during the hardware made permanent during the hardware production of the unit and it is not production of the unit and it is not accessible to users to store accessible to users to store information. information.

  RAM ROM

Function Store the currently active programs and their data.

Stores certain fixed routines such as the boot-up routines.

Volatility RAM is volatile: When the computer is switched off, the contents are lost.

ROM is non-volatile: When the computer is switched off, the contents are not lost.

Changeable

The contents of RAM can be changed or deleted.

The contents of ROM cannot be changed or deleted.

The following table compares RAM and ROM.

CACHE CACHE MEMORYMEMORYCACHE CACHE

MEMORYMEMORYOtherOther types of temporary memory are cache types of temporary memory are cache

(pronounced "cash") and virtual memory.  (pronounced "cash") and virtual memory.  Both of these types of memory supplement Both of these types of memory supplement the computer's primary RAM and perform the computer's primary RAM and perform the same function as RAM.the same function as RAM.

Secondary MemorySecondary MemoryIt is theIt is the Permanent Permanent memory. The information memory. The information

stored is permanent in nature and it uses stored is permanent in nature and it uses external storage devices like external storage devices like Floppy disk, Floppy disk, Magnetic disk, CD-ROM etc.Magnetic disk, CD-ROM etc.

In human terms Primary memory is the In human terms Primary memory is the memory inside our brain and Secondary memory inside our brain and Secondary memory are the notes copy we maintain to memory are the notes copy we maintain to store the information.store the information.

Floppy DiskFloppy Disk

• We used it to store information and it’s We used it to store information and it’s main advantage is that it is main advantage is that it is transportable because of its size.transportable because of its size.

• A diskette comprises a plastic flexible A diskette comprises a plastic flexible disk enclosed inside a tough plastic disk enclosed inside a tough plastic cover. At one end is a window. When the cover. At one end is a window. When the diskette is placed inside a diskette drive, diskette is placed inside a diskette drive, the window is pushed to the side. The the window is pushed to the side. The read-record head inside the drive makes read-record head inside the drive makes contact with the magnetic disk. contact with the magnetic disk.

Hard DiskHard Disk

A number of floppy disk put A number of floppy disk put together in a box and kept in the together in a box and kept in the CPU to store and retrieve CPU to store and retrieve information is a information is a Hard DiskHard Disk..

It consists of a number of rotating platters It consists of a number of rotating platters which are covered with a magnetic film. which are covered with a magnetic film. Information is stored using the magnetic Information is stored using the magnetic properties of the film. The platters rotate properties of the film. The platters rotate from between 5000 and 8000 rpm or faster. from between 5000 and 8000 rpm or faster.

CD - ROMCD - ROM

A CD ROM uses optical technology. A CD ROM uses optical technology. When data is written, small pits When data is written, small pits are burned into the surface using a are burned into the surface using a highly focussed laser beam. These highly focussed laser beam. These are read by another laser beam. are read by another laser beam.

CD-ROMCD-ROM is prepared and read using is prepared and read using Laser BeamLaser Beam. It has a large storage . It has a large storage Capacity and is being widely used Capacity and is being widely used now for archival storagenow for archival storage. .

The Digital Versatile Disk is a development of the storage technology of the CD ROM. Using newer storage methods and higher quality media, a DVD can store about 4 Gb of data. This is enough to store a full length film.

  A zip A zip disk is a removable magnetic disk which disk is a removable magnetic disk which fits into a special zip drive. The surface is coated fits into a special zip drive. The surface is coated with a special scratch resistant material which with a special scratch resistant material which makes a zip disk a very robust storage device. It makes a zip disk a very robust storage device. It comes in a number of capacities: 100, 250 and comes in a number of capacities: 100, 250 and 750 Mb. The speed of a zip drive is faster than all 750 Mb. The speed of a zip drive is faster than all but the very fastest of CD drives. Its robustness but the very fastest of CD drives. Its robustness and speed make it an excellent backup device. and speed make it an excellent backup device. However, its capacity is much less than that of However, its capacity is much less than that of hard drives and tape drives which limits its use hard drives and tape drives which limits its use

for very large amounts of data.for very large amounts of data.

When you think USB flash drive, think USB When you think USB flash drive, think USB Drive. This portable storage products let Drive. This portable storage products let you store, transfer and carry your data you store, transfer and carry your data securely anywhere. Pocket-sized and securely anywhere. Pocket-sized and lightweight, USB Drives can store your lightweight, USB Drives can store your music, images or computer files in a snap. music, images or computer files in a snap.

A new type of external memory is the flash disk or memory stick. This is a solid state device (no moving parts) that connects to the computer via the USB port. It provides a very fast and reliable method of storing data externally. They are at the moment fairly expensive, especially the larger capacity devices. They tend to be limited to a maximum of about 2 Gb. This figure can be expected to increase quite dramatically over time. BACK

INPUT DevicesINPUT Devices

Basic Computer Operation

A computer performs basically five major operations or functions. These are:1) It accepts data or instructions by way of input.2) It stores data by way of storage devices. 3) It can process data as required by the user.4) It gives results in the form of output.

5) It controls all operations inside a computer.

Input Device

Input is the process of entering data and programs into the computer system.The input unit is formed by the input device attached to the computer. The input device takes data from user to the computer in an organized manner for processing.Example of input device: -KeyboardMouseScanner

Keyboard

This is the standard input device attached to all computers.

The layout of keyboard is just like the traditional type-writer with some extra command key and functions keys.

It contains a total of 101-104 keys.

The computer can recognize the electric signals corresponding to the correct key combination and processing is done accordingly.

Let’s see how a Let’s see how a keyboard takes keyboard takes

the input.the input.

Functioning of a Functioning of a keyboard keyboard

When you press the When you press the KK key on key on the keyboard, a plunger the keyboard, a plunger attached to the key pushes attached to the key pushes against the spring or against the spring or rubber dome. The pressure rubber dome. The pressure from your finger overpower from your finger overpower the resistance of the the resistance of the springs or dome so that it springs or dome so that it collapses. This causes two collapses. This causes two electrical contacts to come electrical contacts to come together and electricity together and electricity flows through them making flows through them making a circuit . When you lift a circuit . When you lift your finger the spring or your finger the spring or dome pop the key up and dome pop the key up and the circuit is broken.the circuit is broken.

MouseThe mouse is an input

device also known as pointing device with a roller on its base.

When a mouse rolls on a flat surface the cursor on the screen moves in any direction giving easier and faster movement.

Let’s see how a Let’s see how a Mouse works.Mouse works.

Functioning of a Functioning of a mousemouse

A mouse lets you to control the A mouse lets you to control the onscreen pointer to make onscreen pointer to make menu selection and to menu selection and to manipulate graphics and text manipulate graphics and text on your screen. This mouse on your screen. This mouse has no feet instead a small ball has no feet instead a small ball sticks through its underside sticks through its underside housing. When you move the housing. When you move the mouse the ball moves too. As mouse the ball moves too. As the ball turns it rubs against the ball turns it rubs against two roller and they also turn. two roller and they also turn. One roller senses when mouse One roller senses when mouse moves side-by-side. The other moves side-by-side. The other roller senses up-n-down roller senses up-n-down movement. Together the two movement. Together the two roller can tell which direction roller can tell which direction you moved the mouse.you moved the mouse.

Scanner

Scanner is an optical device that can input any graphical matter and display it back.

The main advantage of direct entry of information is that the user doesn’t have to key the information.

A touchpad is a device that senses A touchpad is a device that senses pressure to guide the pointer on the pressure to guide the pointer on the

computer screen. It is generally a computer screen. It is generally a small square area below the small square area below the

keyboard. As the user moves his/her keyboard. As the user moves his/her finger across the touchpad, the finger across the touchpad, the

pointer moves on the screen. Next pointer moves on the screen. Next to the pad are two buttons used for to the pad are two buttons used for clicking in exactly the same way as clicking in exactly the same way as

those on a mouse.those on a mouse.

A trackball acts as a type of overturned mouse. The ball is on the top side of the object. By rolling the ball you can move the pointer across the screen. Some keyboards have an in-built trackball.

The trackball has been superseded by the touchpad.

A light pen is a device which is sensitive to variations in patterns on a surface. Light pens act like a miniature scanner and can read text as they are dragged across the printed page. This can be transferred directly to the current open document.

A bar code is a pattern of vertical lines in which the spacing and thickness can be used to represent data. A bar code reader is a device that can read and interpret bar codes and input the data into the computer.

A joystick is a device that is familiar for use in games to move objects on the screen. However, it is also used to control the movements in computerised industrial machines such as lathes. It consists of a small vertical lever which can move in any direction. These movements are translated to the computer which in turn uses them to control the movements of machinery.

Instead of film, a digital camera uses a light sensitive screen at the back of the camera. A small computer inside the camera converts the pattern on the screen into a standard graphics file which can then be transferred to a computer.

A microphone translates speech into an electronic signal. Modern speech recognition software is able to translate this into either commands or data. This enables the user to use a microphone as an alternative to the keyboard.

Magnetic Ink Character Recognition is a character recognition system that uses special ink and characters. When a document that contains this ink needs to be read, it passes through a machine, which magnetizes the ink and then translates the magnetic information into characters. MICR technology is used by banks. Numbers and characters found on the bottom of checks (usually containing the check number, sort number, and account number) are printed using Magnetic Ink. To print Magnetic Ink need, you need a laser printer that accepts MICR toner. MICR provides a secure, high-speed method of scanning and processing information.

Optical character recognition, usually abbreviated to OCR, is computer software designed to translate images of handwritten or typewritten text (usually captured by a scanner) into machine-editable text, or to translate pictures of characters into a standard encoding scheme representing them (e.g. ASCII or Unicode). OCR began as a field of research in pattern recognition, artificial intelligence and machine vision. Though academic research in the field continues, the focus on OCR has shifted to implementation of proven techniques.

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Output DevicesOutput Devices

Output DevicesOutput DevicesOutput is the process of producing Output is the process of producing

results from the raw data for getting results from the raw data for getting useful information. useful information.

Mainly there are two principal devices to Mainly there are two principal devices to output information from a computer. output information from a computer. These are:These are: MonitorMonitor PrinterPrinter

Monitor / Visual Display UnitMonitor / Visual Display UnitThe most popular output device is The most popular output device is

visual device unit. A keyboard visual device unit. A keyboard is used to input data and is used to input data and monitor is used to display the monitor is used to display the input data and to receive input data and to receive messages from the computer. messages from the computer.

A monitor has its own box which is A monitor has its own box which is separated from the main separated from the main computer system and is computer system and is connected to the computer by connected to the computer by cable. cable.

In some system it is compact with In some system it is compact with the system unit.the system unit.

It can be colored or monochrome.It can be colored or monochrome.

Let’s see how monitor Let’s see how monitor functions.functions.

How monitor worksHow monitor worksSignals from computer’s video card Signals from computer’s video card

are loaded into three electron are loaded into three electron guns at the base of the monitor. guns at the base of the monitor. There is one gun for each of three There is one gun for each of three color Red, Blue and Green. These color Red, Blue and Green. These three colors when mix together three colors when mix together can create all the colors you see can create all the colors you see on your screen. Now these gun on your screen. Now these gun don’t shoot bullets instead they don’t shoot bullets instead they shoot powerful beams of shoot powerful beams of electrons toward the face of the electrons toward the face of the monitor. The beam pass through monitor. The beam pass through a deflection unit. It uses the a deflection unit. It uses the magnetism to bend the electronic magnetism to bend the electronic beam So that they can sweep beam So that they can sweep across the entire screen and across the entire screen and create the picture we see.create the picture we see.

PrinterPrinterPrinter is an important Printer is an important

output device which can output device which can be used to get a hard be used to get a hard copy or printed copy of copy or printed copy of the processed data or the processed data or result on paper.result on paper.

There are different types There are different types of printer that are of printer that are designed for different designed for different types of application. types of application. Printers are classified asPrinters are classified as– Impact Impact – Non-Impact Non-Impact

printerprinter

Impact Printer Impact Printer Impact printers use Impact printers use

the familiar type-the familiar type-writer approach of writer approach of hammering a hammering a typeface against typeface against the paper and the paper and inked ribbon.inked ribbon.

E.g.. DOT MATRIXE.g.. DOT MATRIX

Non-Impact PrinterNon-Impact PrinterNon-Impact printer do not Non-Impact printer do not

impact or hit a ribbon to impact or hit a ribbon to paper.paper.

They use electrostatic They use electrostatic chemical and inkjet chemical and inkjet technologies.technologies.

These can produce color These can produce color printing and elaborate printing and elaborate graphics.graphics.E.g. E.g. Laser printerLaser printer

Inkjet printerInkjet printer

A plotter consists of a device that can move paper both backwards and forwards. On the top of the device one or more pens are able to move horizontally across the paper. The combined movement of the pens horizontally across the paper and the vertical movement of the paper allows complex continuous diagrams to be drawn.

Some plotters allow different colour pens to be used to create diagrams in multiple colours.

In other types of plotters, the paper lies on a flat bed. The mechanics of the plotter are so designed that the pens can move both across and down the paper to create the diagram.

Modern computers using the appropriate software can turn text in a document into audible speech. This is known as speech synthesis. Other types of software allow music and other sounds to be created and played back.

The sound is transmitted through a speaker in the same way it is in a sound system or radio.

Some devices function as both input and output devices.

A touchscreen is a special type of screen in which the screen not only displays output but also responds to being touched. A typical example is their use in autotellers at banks. Part of the screen contains information. Other parts may contain a menu. When you touch one of the icons on the screen, the system responds to the associated command.

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