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1.1 INTRODUCTION

Although, the term ‘Information Technology’ is becoming more familiar to the common man, somepeople still interested to know, what is information technology?

Information, meaning processed form of raw data, is something to be valued with your life intoday’s world. A person possessing right kind of information and using it at the right time can surelywork wonders. From the credit card numbers, which we use for shopping, to the confidential bankaccount details, everything is stored in the form of binary digits in computers. These details can be usedor misused depending on what kind of people have authorized or unauthorized access to it. With thehelp of information technology (IT) and our increasing dependency on machines, our life has becomefar easier, but we are more vulnerable now than before.

When computer and communications technologies are combined, the result is informationtechnology or infotech. Information technology is a general term that describes any technology that helps toproduce, manipulate, store, communicate and/or disseminate information . Presumably, when speaking of IT as

a whole, it is noted that the use of computers and information are associated.1.1.1 Let’s Define IT

Information technology (IT), as defined by the Information Technology Association of America (ITAA),is “the study, design, development, implementation, support or management of computer-basedinformation systems, particularly software applications and computer hardware. Information technology is the use of computers and software to manage information . In some companies, this is referred to asManagement Information Services (or MIS) or simply as Information Services (or IS). The informationtechnology department of a large company would be responsible for storing information, protectinginformation, processing the information, transmitting the information as necessary, and later retrievinginformation as necessary.

Information Technology or IT mainly deals with the computer applications. The common workenvironment today is totally dependent on computers. This has led to the need to develop and consistentlyupgrade dedicated computer software like project management software, for a number of relatedrequirements. These include storage and protection of content, processing and transmitting of dedicatedinformation and the secured retrieval of information, when and as required. IT promotes computingtechnology, covering everything from installing applications to developing databases.

We use the term information technology or IT to refer to an entire industry.

INTRODUCTION TO

INFORMATION TECHNOLOGY



It Infrastructure & Management

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1.1.2 Evolution of IT

As a concept, it has evolved from the basic usage of computers and processing of information in anyindustry. In relative terms, it was not long ago that the IT department might have consisted of a singlecomputer operator, who might be storing data on magnetic tape, and then putting it in a box down inthe basement somewhere. The history of IT is fascinating. Domsic, who worked as a computer managerfor an automotive related industry, is supposed to have created the term to modernize the outdatedphrase “data processing”. The Oxford English Dictionary, however, defined information technology as“the branch of technology concerned with the dissemination, processing, and storage of information, especially bymeans of computers” provides an illustrative quote from the year 1958 that predates the so-farunsubstantiated Domsic coinage.

The term ‘Information Technology’ evolved in the 1970s and if we consider a medium or largecompany providing goods or services, its information technology department will be responsible for

storing, protecting, processing, retrieving and transmitting the information. IT is a wide and variedsector, and is represented in some form in almost all the industries. It is a blend of computers andcommunication technology where IT professionals perform variety of duties, ranging from developmentand installation of applications to designing complex computer networks and databases. The informationtechnology industry consists of computers, communication mediums, peripherals, electronics-relatedorganizations, software and services. Usage of information technology for the completion of tasks in anyorganization, speeds up the processing and information mobility, and also improves the reliability andintegrity of information.

1.1.3 Information Technology: Great Future Ahead

Information Technology Departments will be increasingly concerned with data storage and management,and will find that information security will continue to be at the top of the priority list. Cloud computingremains a growing area to watch. The job outlook for those within Information Technology is strong,with data security and server gurus amongst the highest paid techies.

The cost of transmitting information has fallen dramatically, and according to a study, the cost of transfer of one trillion bits of information from one part of the world to the other part has come downfrom large amounts to a meager amount today. With the help of Internet technology, emailing a documentof 40 pages from India to America costs nothing as compared to the faxing price or even sending it bycourier. Hence, it can be clearly seen that there are many advantages of information technology and ithas drastically decreased the cost of information transfer. It has also increased the efficiency of employeesin all organizations, allowing them to focus on core competencies rather than the technological issues.

Information Technology is on the way ahead building the bridge between otherwise not easily mingledsocieties.

1.1.4 Components of Information Technology

Some components of Information Technology here as under:



Introduction to Information Technology

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(a) Computers

Computers are very important in order to store and process data. Depending on the size, cost andprocessing ability, computers are divided into four categories. They are mainframes, supercomputer,minicomputers and microcomputers (desktops or personal computers).

(b) Servers

A server is a combination of hardware and software, and is used to provide services to the client computers.These services generally include storage and retrieval of information. A standalone computer can alsoact as a server, provided it’s running on server operating system.

(c) Database Management Systems (DBMS)

Some components of Inforamtion Technology are as follows: Database Management System is basically

a set of software programs, which manages the storage and retrieval, and organizes the information in acomputer. This information is in the form of a database and is managed with the help of software. TheDBMS accepts requests from the application program and instructs the operating system to transfer theappropriate data. There are various departments to monitor the flow of information, which include:

System Administrators,IT Managers,Database Administrators andChief Information Officers (CIOs).

(d) Networking

A computer network is a collection of computers and peripherals connected to each other throughdifferent modes. These modes can be wired or wireless. The network allows computers to communicatewith each other (share information and resources like printers, scanners, etc.).

1.1.5 Advantages of Information Technology

Some of the advantages of information technology include:Globalization: Information technology has not only brought the world closer together, but ithas allowed the world’s economy to become a single interdependent system. This means that wecan not only share information quickly and efficiently, but we can also bring down barriers of linguistic and geographic boundaries. The world has developed into a global village due to the

help of information technology allowing countries like Chile and Japan who are not only separatedby distance but also by language to share ideas and information with each other.Communication: With the help of information technology, communication has also becomecheaper, quicker and more efficient. We can now communicate with anyone around the globe bysimply text messaging them or sending them an email for an almost instantaneous response. The




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Internet has also opened up face-to-face direct communication from different parts of the worldthanks to the helps of video conferencing.

Cost effectiveness: Information technology has helped to computerize the business process thusstreamlining businesses to make them extremely cost effective money making machines. This inturn increases productivity, which ultimately gives rise to profits that, means better pay and lessstrenuous working conditions.Bridging the cultural gap: Information technology has helped to bridge the cultural gap byhelping people from different cultures to communicate with one another, and allow for theexchange of views and ideas, thus increasing awareness and reducing prejudice.Time effectiveness: Inforamtion Technology has made it possible for businesses to be open 24 x7all over the globe. This means that a business can be open anytime anywhere, making purchasesfrom different countries easier and more convenient. It also means that you can have your goods

delivered right to your doorstep with having to move a single muscle.Creation of new jobs: Probably the best advantage of information technology is the creation of new and interesting jobs. Computer programmers, Systems analyzers, Hardware and Softwaredevelopers and Web designers are just some of the many new employment opportunities createdwith the help of IT.

1.1.6 Technology: Very Cost Effective

Technology has contributed towards savings in many ways mentioned below:(a) Savings from the technology automating what was previously manual(b) Savings from data rationalization - e.g., through Master Data management facilitated by the

technology(c) Savings from business process changes the technology facilitates(d) Savings from structural changes (e.g., moving to shared services enabled by the technology)(e) Savings from optimized information (back then constraint based decision tools were starting to

allow for smaller physical asset bases)(f) Savings from not having to invest in Y2K fixes(g) Savings from disbanding other legacy systems (e.g., through data center consolidation. Keyword

is disbanding, not keeping it around)(h) Revenue increments clearly attributable to the new technology (rare back then - and even

today)1.1.7 Disadvantages of Information Technology

Some disadvantages of information technology include:Unemployment: While information technology may have streamlined the business process ithas also crated job redundancies, downsizing and outsourcing. This means that a lot of lower and




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middle level jobs have been done away with causing more people to become unemployed.Privacy: Though information technology may have made communication quicker, easier andmore convenient, it has also bought along privacy issues. From cell phone signal interceptions toemail hacking, people are now worried about their once private information becoming publicknowledge.Lack of job security: Industry experts believe that the internet has made job security a big issueas since technology keeps on changing with each day. This means that one has to be in aconstant learning mode, if he or she wishes for their job to be secure.Dominant culture: While information technology may have made the world a global village, ithas also contributed to one culture dominating another weaker one. For example it is nowargued that US influences how most young teenagers all over the world now act, dress andbehave. Languages too have become overshadowed, with English becoming the primary mode of

communication for business and everything else.1.2 COMPUTER FUNDAMENTALS

Computers form the most important component of Information Technology.A computer is a programmable machine (or more precisely, a programmable sequential state machine).There are two basic kinds of computers: analog and digital.

1.2.1 Analog Computer

Analog computers are analog devices. That is, they have continuous states rather than discrete numberedstates. An analog computer can represent fractional or irrational values exactly, with no round off. They

are almost never used outside of experimental settings.1.2.2 Digital Computer

A digital computer is a programmable-clocked sequential state machine. A digital computer uses discretestates. 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.

1.2.3 Types of Computer

There are many types of computers, but personal computers such as desktop and laptop computers areprobably the two types of computers that you think of first.

Desktop ComputersThe term desktop computer originated when the computer case was wide and flat, and was designedspecifically to fit on your desktop with the monitor on the top. Many people use desktop computers, ordesktops as they are often referred to, at work, home, school, or the library. They can be small, medium




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Figure 1.1 Desktop Computer

or large in style, and usually sit on a desk. The term desktop actually refers to the casing, or the tower.Once you add a monitor, mouse, and a keyboard, you have what is typically known as a desktop computer(fig. 1.1). Most desktop computers are easy to upgrade and expand or add new parts. In addition toexpandability, another benefit of desktop computers is the cost. If you compare a desktop computer with128 MB of RAM and a 2 GB hard drive to a laptop with the same features, you will most likely find thatthe desktop computer is priced lower.

Two popular types of personal computers are the IBM compatible and Macintosh computers. Thefirst personal computer was produced by IBM in 1981 and was called the IBM PC. In 1984, AppleComputer introduced the Macintosh, or Mac, and it became the first widely sold personal computerwith a graphical user interface or GUI (pronounced gooey). Although both IBM and Apple computersare personal computers, the term PC came to refer to IBM or IBM-compatible personal computers.Apple now produces a Macintosh computer called the iMac, which is a desktop computer that featuresan all-in-one design. This means all the internal components are located behind the monitor, ratherthan in a tower case, which is customary in desktop computers. While our training is intended forpeople who use PCs and the Windows operating system, some of our information also applies to Macintoshcomputers.

Laptop Computers

Laptops are battery or AC-powered personal computers that can be easily carried and used in a varietyof locations. The second type of computer that you may be familiar with is a laptop computer, or laptops(fig. 1.2) as they are often referred to. A laptop computer is sometimes called a notebook computerbecause of its size. A quick glance at the size of a laptop and you might guess that it would be difficult toexpand or upgrade. While the desktop computer case is relatively easy to open and access internalcomponents, the small laptop case makes this more difficult in comparison; however, the primarybenefit of a laptop computer is its small size and easy portability.




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Figure 1.2 Laptop Computer

Workstation/Server

You may hear someone refer to a computer as a workstation or a server, especially at work. You maywonder how these two items are different from desktop computers. Workstations are similar to desktopcomputers, but are more powerful and are usually connected to a network.

Servers are specialized computers that store and deliver, or “serve up,” information to other computerson a network. There are many different types of servers such as file servers, database servers, and webservers. For example, employees at a company might store all the business documents on a file server so

that they can share files and access them from any computer on the network. When you use yourbrowser to click a link, a web server delivers the page you requested on the Internet, the biggest networkin the world.

1.2.4 Components of a Computer

Two of the important constituents of a computer are hardware, which represents the physical parts of the computer and software which represents the programs or set of instructions to the computer. Apartfrom these two main elements computer works on data , people and procedures. These five elements arelisted below as:

Hardware

SoftwareDataPeople andProcedures




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1.2.5 Physical Components of Computer

RAM ROM

controlunit

CentralProcessing

Unit

arithmeticlogic unit

floatingpoint unit

Main Memory

input subsystem external storage output

Figure 1.3 Physical Components of computer

If we go further deep into exploring the parts of computer, it is divided into following elements:ProcessorArithmetic and logic unitControl unitMain storageExternal storageInputOutput

1.2.6 Processor

The processor is the part of the computer that actually does the computations. This is sometimescalled an MPU (main processor unit) or CPU (central processing unit or 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 mostcommon special function unit being a floating point unit for floating point arithmetic).Some computers have more than one processor. This is called multi-processing.

Kinds of Processors

The major kinds of digital processors are:




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CISC: CISC stands for Complex Instruction Set Computer. Mainframe computers and minicomputerswere CISC processors, with manufacturers competing to offer the most useful instruction sets. Many of

the first two generations of microprocessors were also CISC.RISC: RISC stands for Reduced Instruction Set Computer. RISC came about as a result of academicresearch that showed that a small well designed instruction set running compiled programs at highspeed could perform more computing work than a CISC running the same programs (although veryexpensive hand optimized assembly language favored CISC).DSP: DSP stands for Digital Signal Processing. DSP is used primarily in dedicated devices, such asMODEMs, digital cameras, graphics cards, and other specialty devices.Hybrid: Hybrid processors combine elements of two or three of the major classes of processors.

1.2.7 Arithmetic and Logic Unit

An arithmetic/logic unit (ALU) performs integer arithmetic and logic operations. It also performs shiftand rotate operations and other specialized operations. Usually floating point arithmetic is performedby a dedicated floating point unit (FPU), which may be implemented as a co-processor.

ALU performs integer arithmetic and logic operations. It also performs shift and rotate operationsand other specialized operations. Usually floating point arithmetic is performed by a dedicated FPUwhich may be implemented as a co-processor.

1.2.8 Control Unit

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

A bus is a set (group) of parallel lines that information (data, addresses, instructions, and otherinformation) 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 that is inside the processor, moving data, addresses, instructions, and otherinformation between registers and other internal components or units. An external bus is a bus that isoutside of the processor (but inside the computer), moving data, addresses, and other informationbetween major components (including cards) inside the computer. Some common kinds of buses are thesystem bus, a data bus, an address bus, a cache bus, a memory bus, and an I/O bus.

1.2.9 Main Storage

Main storage is also called memory or internal memory (to distinguish from external memory, such ashard drives).

Random Access Memory (RAM)

Random Access Memory is the basic kind of internal memory. RAM is called “random access” becausethe processor or computer can access any location in memory (as contrasted with sequential accessdevices, which must be accessed in order). RAM is also called Read Write Memory. RAM has been made




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from reed relays, transistors, integrated circuits, magnetic core, or anything that can hold and storebinary 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 wasmagnetic core, so many older programmers will refer to main memory as core memory even when theRAM is made from more modern technology. Static RAM is called static because it will continue tohold 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 dynamic memory. It is possible to have battery backup for devices that are normally dynamic to turn them into static memory.

Read Only Memory (ROM)

ROM is typically used to store things that will never change for the life of the computer, such as lowlevel portions of an operating system. Some processors (or variations within processor families) mighthave RAM and/or ROM built into the same chip as the processor (normally used for processors used instandalone devices, such as arcade video games, ATMs, microwave ovens, car ignition systems, etc.).EPROM is Erasable Programmable Read Only Memory, a special kind of ROM that can be erased andreprogrammed with specialized equipment (but not by the processor it is connected to). EPROMs allowmakers of industrial devices (and other similar equipment) to have the benefits of ROM, yet also allowfor updating or upgrading the software without having to buy new ROM and throw out the old (theEPROMs are collected, erased and rewritten centrally, then placed back into the machines).

Registers and Flags

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 havespecialized 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 pointregisters). Some processors separate integer data and address registers, while other processors havegeneral purpose registers that can be used for both data and address purposes. A processor will typicallyhave one to 32 data or general purpose registers (processors with separate data and address registerstypically split the register set in half). Many processors have special floating point registers (and someprocessors have general purpose registers that can be used for either integer or floating point arithmetic).Flags are single bit memory used for testing, comparison and conditional operations.

1.2.10 External Storage

External storage (also called auxillary storage) is any storage other than main memory. In modern timesthis 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 andremoveable media is blurred. Other kinds of external storage include tape drives, drum drives, papertape, and punched cards. Random access or indexed access devices (such as hard drives, removeablemedia, and drum drives) provide an extension of memory (although usually accessed through logical file




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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).1.2.11 Input/Output Devices

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 adevice is I/O, read-only or write-only, external devices can be classified as character and block devices.

Character Device

A character device is one that inputs or outputs data in a stream of characters, bytes, or bits. It can furtherbe 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 devicesinclude 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 bitsincluded in the data stream). Each group usually corresponds to a single character of data. Rarely therewill be a larger group of bits (word, longword, doubleword, etc.). The most common parallel device is aprinter (although most modern printers have both a serial and a parallel connection, allowing greaterconnection flexibility).

Block Device

A block device moves large blocks of data at once. This may be physically implemented as a serial orparallel stream of data, but the entire block gets transferred as single packet of data. Most block devicesare random access (that is, information can be read or written from blocks anywhere on the device).Examples of random access block devices include: hard disks, floppy disks and drum drives. Examples of sequential access block devctises include magnetic tape drives and high-speed paper tape readers.

Input Decices

Input devices are devices that feed data into a computer.Pure input devices include, punched card readers, paper tape readers, keyboards, mice, drawing tablets,touchpads, trackballs and game controllers. Devices that have an input component include: magnetictape drives, touchscreens and dumb terminals.

Output Devices

Output devices are devices that bring information out of a computer.Pure output devices include card punches, paper tape punches, LED displays (for light emitting diodes),monitors, printers and pen plotters.




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Devices that have an output component include: magnetic tape drives, combination paper tapereader/punches, teletypes, and dumb terminals.

1.3 DEVICES: HOW DO THEY WORK

1.3.1 The Magnetic Tape Drive

Magnetic tape drive is an external storage device used to store and retrieve data sequentially. Itsworking is similar to audio tape. The tape drops in two loops to either side of the drive so that it can passat a constant speed across the heads. The reservoirs are triggered by lights and photo-sensors. Thestandard tape is 9 track, 1/2 inch wide (9 parallel tracks running along the tape - 8 are for data and thelast is a parity bit).

Tape density is defined in terms of bytes/inch (the standard is 1600 bytes per inch, the maximum is6250 bytes per inch). The standard tape is 2400 feet long. Between blocks stored on tape is the inter-

record gap (0.6 inches). This is the smallest possible distance to allow the drive to stop and start againThe Tape

There are two parts to any audio magnetic recording system: the recorder itself (which also acts as theplayback device) and the tape it uses as the storage medium.

Figure 1.4 Tape

The tape itself is actually very simple. It consists of a thin plastic base material, and bonded to this baseis a coating of ferric oxide powder. The oxide is normally mixed with a binder to attach it to the plastic,and it also includes some sort of dry lubricant to avoid wearing out the recorder.

Iron oxide (FeO) is the red rust we commonly see. Ferric oxide (Fe 2O3) is another oxide of iron.Maghemite or gamma ferric oxide are common names for the substance.

This oxide is a ferromagnetic material, meaning that if you expose it to a magnetic field it ispermanently magnetized by the field. That ability gives magnetic tape two of its most appealing features:

You can record anything you want instantly and the tape will remember what you recorded forplayback at any time.You can erase the tape and record something else on it any time you like.




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These two features are what make tapes and disks so popular — they are instant and they are easilychanged.

Audio tapes have gone through several format changes over the years. The original format was nottape at all, but actually was a thin steel wire. The wire recorder was invented in 1900 by ValdemarPoulsen. German engineers perfected the first tape recorders using oxide tapes in the 1930s. Tapesoriginally appeared in a reel-to-reel format.

Reel-to-reel tapes were common until the compact cassette or “cassette tape” took hold of themarket. The cassette was patented in 1964 and eventually beat out 8-track tapes and reel-to-reel tobecome the dominant tape format in the audio industry.

If you look inside a compact cassette, you will find that it is a fairly simple device. There are two spoolsand the long piece of tape, two rollers and two halves of a plastic outer shell with various holes and cutoutsto hook the cassette into the drive. There is also a small felt pad that acts as a backstop for the record/

playback head in the tape player. In a 90-minute cassette, the tape is 443 feet (135 meters) long.The Tape Recorder

The simplest tape recorders are very simple indeed, and everything from a Walkman to a high-endaudiophile deck embodies that fundamental simplicity.

The basic idea involves an electromagnet that applies a magnetic flux to the oxide on the tape. Theoxide permanently “remembers” the flux it sees. A tape recorder’s record head is a very small, circularelectromagnet with a small gap in it, like this:

Figure 1.5 Tape recorder

This electromagnet is tiny — perhaps the size of a flattened pea. The electromagnet consists of an ironcore wrapped with wire, as shown in the figure. During recording, the audio signal is sent through thecoil of wire to create a magnetic field in the core. At the gap, magnetic flux forms a fringe pattern tobridge the gap (shown in red), and this flux is what magnetizes the oxide on the tape. During playback,the motion of the tape pulls a varying magnetic field across the gap. This creates a varying magnetic fieldin the core and therefore a signal in the coil. This signal is amplified to drive the speakers.




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In a normal cassette player, there are actually two of these small electromagnets that together areabout as wide as one half of the tape’s width. The two heads record the two channels of a stereo program

when you turn the tape over, you align the other half of the tape with the two electromagnets.When you look inside a tape recorder, you generally see that at the top of this picture are the two

sprockets that engage the spools inside the cassette. These sprockets spin one of the spools to take upthe tape during recording, playback, fast forward and reverse. Below the two sprockets are two heads.The head on the left is a bulk erase head to wipe the tape clean of signals before recording. The head inthe center is the record and playback head containing the two tiny electromagnets

1.3.2 Hard Disk Drive

The Hard Disk Drive installs in one of the 3-1/2 inch internal drive bays in the PC. It is secured bymachine screws. It is powered by a 4 conductor cable coming from the power supply. Data to and fromthe motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.

Figure 1.6 Hard Disk Drive

Data is stored magnetically on multiple rigid disks that are stacked up like pancakes. Small arms withmagnetic pickups move rapidly back and forth across the top and bottom surface of each disk in thedrive. The sensors float just a few microns above the rotating disk surface and can read and write data atvery high rates.

Most commercially available hard drives rotate at 5400 or 7200 RPM (revolutions per minute)

which translates to 90 or 120 revolutions per second respectively. The data transfer rate from the driveto the motherboard is 33 Mbytes/second in bursts. Newer drives are capable of higher speeds up to 66Mbytes/sec. To use this faster drive, the PC must have an ATA/66 interface that is capable of keeping upwith it.

Nearly every desktop computer and server in use today contains one or more hard-disk drives. Everymainframe and supercomputer is normally connected to hundreds of them.




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Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameterholding just a few megabytes. They were originally called “fixed disks” or “Winchesters” (a code name

used for a popular IBM product). They later became known as “hard disks” to distinguish them from“floppy disks.” Hard disks have a hard platter that holds the magnetic medium, as opposed to theflexible plastic film found in tapes and floppies.

At the simplest level, a hard disk is not that different from a cassette tape. Both hard disks andcassette tapes use the same magnetic recording techniques Hard disks and cassette tapes also share themajor benefits of magnetic storage—the magnetic medium can be easily erased and rewritten, and it will“remember” the magnetic flux patterns stored onto the medium for many years.

A typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes.Data is stored onto the disk in the form of files. A file is simply a named collection of bytes. The bytesmight be the ASCII codes for the characters of a text file, or they could be the instructions of a software

application for the computer to execute, or they could be the records of a data base, or they could be thepixel colors for a GIF image. No matter what it contains, however, a file is simply a string of bytes. Whena program running on the computer requests a file, the hard disk retrieves its bytes and sends them tothe CPU one at a time.There are two ways to measure the performance of a hard disk:

Data rate: The data rate is the number of bytes per second that the drive can deliver to the CPU.Rates between 5 and 40 megabytes per second are common.Seek time: The seek time is the amount of time between when the CPU requests a file and whenthe first byte of the file is sent to the CPU. Time between 10 and 20 milliseconds are common.

The other important parameter is the capacity of the drive, which is the number of bytes it can hold

Storing the Data

Data is stored on the surface of a platter in sectors and tracks. Tracks are concentric circles, and sectorsare pie-shaped wedges on a track, like the following figure:

Figure 1.7 Surface of Platter




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A typical track is shown in yellow; a typical sector is shown in blue. A sector contains a fixednumber of bytes — for example, 256 or 512. Either at the drive or the operating system level, sectors are

often grouped together into clusters.The process of low-level formatting a drive establishes the tracks and sectors on the platter. The

starting and ending points of each sector are written onto the platter. This process prepares the drive tohold blocks of bytes. High-level formatting then writes the file-storage structures, like the file-allocationtable, into the sectors. This process prepares the drive to hold files.

1.3.3 Cassette Tape vs. Hard Disk

Let’s look at the big differences between cassette tapes and hard disks:

Figure 1.8 Cassette tape vs Hard Disk

The magnetic recording material on a cassette tape is coated onto a thin plastic strip. In a hard disk, themagnetic recording material is layered onto a high-precision aluminum or glass disk. The hard-diskplatter is then polished to mirror-type smoothness.

With a tape, you have to fast-forward or reverse to get to any particular point on the tape. This cantake several minutes with a long tape. On a hard disk, you can move to any point on the surface of thedisk almost instantly.

In a cassette-tape deck, the read/write head touches the tape directly. In a hard disk, the read/writehead “flies” over the disk, never actually touching it.

The tape in a cassette-tape deck moves over the head at about 2 inches (about 5.08 cm) per second.A hard-disk platter can spin underneath its head at speeds up to 3,000 inches per second (about 170mph or 272 kph)!

The information on a hard disk is stored in extremely small magnetic domains compared to acassette tape’s. The size of these domains is made possible by the precision of the platter and the speedof the medium.

Because of these differences, a modern hard disk is able to store an amazing amount of informationin a small space. A hard disk can also access any of its information in a fraction of a second.




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1.3.4 Floppy Disk Drive

The Floppy Disk Drive (FDD) installs in one of the external drive bays at the front of the PC case andis secured by machine screws. External means you can access the drive from the outside. A cable powersit with a 4-pin connector that comes from the power supply. It transfers data to and from the motherboardby means of a 34 pin ribbon cable. It stores data magnetically on a removable floppy disk. A pickup armin the drive floats above the disk surface. The arm moves rapidly back and forth across the disk surfaceas a small magnetic sensor at the end of the arm reads and writes data on the rotating disk surface.

Floppy disks hold 1.44 Mbytes, which at one time was a large amount of data. Today many programsand files are much larger than this. In spite of being surpassed in size by CD and DVD, floppy drives arestill found on many newer PCs.

The FDD was invented at IBM by Alan Shugart in 1967. The first floppy drives used an 8-inch disk(later called a “diskette” as it got smaller), which evolved into the 5.25-inch disk that was used on thefirst IBM Personal Computer in August 1981. The 5.25-inch disk held 360 kilobytes compared to the1.44 megabyte capacity of today’s 3.5-inch diskette.

The 5.25-inch disks were dubbed “floppy” because the diskette packaging was a very flexible plasticenvelope, unlike the rigid case used to hold today’s 3.5-inch diskettes.

By the mid-1980s, the improved designs of the read/write heads, along with improvements in themagnetic recording media, led to the less-flexible, 3.5-inch, 1.44-megabyte (MB) capacity FDD in usetoday. For a few years, computers had both FDD sizes (3.5-inch and 5.25-inch). But by the mid-1990s,the 5.25-inch version had fallen out of popularity, partly because the diskette’s recording surface couldeasily become contaminated by fingerprints through the open access area.

Parts of a Floppy Disk Drive

(a) The Disk: Disk is a flat, thin round object, an information storage device for a computer, onwhich data is stored - either magnetically or of optically.The floppy disk and the magnetic tape have lot in common, which are given as follows:

Both use a thin plastic base material coated with iron oxide. This oxide is a ferromagneticmaterial, meaning that if you expose it to a magnetic field it is permanently magnetized bythe field.Both can record information instantly.Both can be erased and reused many times.Both are very inexpensive and easy to use.

If you have ever used an audio cassette, you know that it has one big disadvantage — it is a sequentialdevice. The tape has a beginning and an end, and to move the tape to another song later in the sequenceof songs on the tape you have to use the fast forward and rewind buttons to find the start of the song,since the tape heads are stationary. For a long audio cassette tape it can take a minute or two to rewindthe whole tape, making it hard to find a song in the middle of the tape.




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A floppy disk, like a cassette tape, is made from a thin piece of plastic coated with a magneticmaterial on both sides. However, it is shaped like a disk rather than a long thin ribbon. The tracks are

arranged in concentric rings so that the software can jump from “file 1” to “file 19” without having tofast forward through files 2-18. The diskette spins like a record and the heads move to the correct track,providing what is known as direct access storage.

Figure 1.9 Floppy Disk (b) The Drive: Disk drive is a devie which allows a computer to read from and write on to computer

disks.The major parts of a Floppy Disk Drive include:Read/Write Heads : Located on both sides of a diskette, they move together on the same assembly.The heads are not directly opposite each other in an effort to prevent interaction between writeoperations on each of the two media surfaces. The same head is used for reading and writing,while a second, wider head is used for erasing a track just prior to it being written. This allows thedata to be written on a wider “clean slate,” without interfering with the analog data on anadjacent track.Drive Motor : A very small spindle motor engages the metal hub at the center of the diskette,spinning it at either 300 or 360 rotations per minute (RPM).Stepper Motor : This motor makes a precise number of stepped revolutions to move the read/ write head assembly to the proper track position. The read/write head assembly is fastened to thestepper motor shaft.




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Mechanical Frame: A system of levers that opens the little protective window on the diskette toallow the read/write heads to touch the dual-sided diskette media. An external button allows the

diskette to be ejected, at which point the spring-loaded protective window on the diskettecloses.Circuit Board : Contains all of the electronics to handle the data read from or written to thediskette. It also controls the stepper-motor control circuits used to move the read/write heads toeach track, as well as the movement of the read/write heads toward the diskette surface.

The read/write heads do not touch the diskette media when the heads are traveling between tracks.Electronic optics check for the presence of an opening in the lower corner of a 3.5-inch diskette (or a notchin the side of a 5.25-inch diskette) to see if the user wants to prevent data from being written on it.

Figure 1.10 Driver

1.3.5 Compact Disk Drive

The Compact Disk Drive installs in one of the external 5-1/4 inch drive bays in the front of the PC case.It is secured by machine screws. Some manufacturers offer special rail-like systems that mount on theCDD. These allow the drive to be removed from the PC without having to remove any screws.

Figure 1.11 Disk Data is stored optically on the surface of the disk. A laser attached to an arm that moves back and forthacross near the disk surface and sends light toward the disk surface which is coated with of a thin layerof aluminum.




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Smooth areas called a lands reflect the light back to a photo diode located near the laser. Thereflected light is read as a 1. Areas called pits are where the aluminum has been removed. When the laser

light hits these, it is scattered and very little is picked up by the photo diode. The absence of light is readas a 0.CDD have become the predominant removable storage media for PCs and can store 700 Mbytes of

data.A 4-pin cable from the power supply plugs into the CDD and provides power to it.

Data to and from the motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.There are two types of Compact Disk drives available for PCs.

CD-ROM (read only memory) is the older type. As the title implies it can only read CDs. It canread any standard CD and most CD-R type disks. It may be able to read some types of CD-RWdisks too.CD-RW (ReWritable) units can read and write CD-R and CD-RW type disks. It can also readstandard CD type disks.

The reading and writing speed of the CD drives is expressed in terms of multiples of some standard speedand are expressed as nx to indicate that this unit is ‘n’ times faster than the standard used.

The history of the compact disk (CD) started with the videodisk in the form of Video Long Play(VLP) read-only systems. But, it was actually introduced in about 1982, the CD-DA (compact disk-digital audio) was introduced to the market jointly by Phillips and Sony. It stored a high-quality stereoaudio signal in a digital form. These systems became a huge success. In 1985, the compact disk-digitalaudio technology was extended for computer storage.

Parts of Compact DiskThe compact disk consists of:(a) The label(b) The protective layer(c) The reflective layer(d) The substrate layer.A laser beam of approximately 780 nm wave length is focused on the data side of the disk into a spot of about 1 micron in diameter. The laser moves in the radial direction over the fast spinning disk andscans the data track for the intensity of the reflected light.

The reason for the high reliability of the CD is good protection of the data from damage both insideand outside CD drive. Outside, the data layer is protected by tough 1.2 mm thick layer of polycarbonateon one side and 10-20 microns of a protective lacquer layer on the other side. Small scratches on thesurface of CD do not directly erase the data, but just create additional areas of light scattering. This canconfuse the drive’s electronic, which is also much less sensitive to radial scratches than to thecircumferential ones. Gentle polishing of the scratch can (in many cases) make the CD readable again.




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But, this is rarely necessary thanks to the large size of the laser spot on the surface of the PC layer - about1 mm. This large spot diameter “integrates” the signal over the large area making the system much less

sensitive to dirt and scratches on the disk surface.Inside the drive, the disk and the drive’s optics are separated by a distance of about 1 mm, making

mechanical interaction and “crashes”, even with wavy disks and imperfect clamping almost impossible.

1.3.6 Digital Video Disk Drive

DVD also known as the Digital Versatile Disk drive, installs in one of the external 5 1/4 inch drive baysin the PC. It is secured by machine screws. Some manufacturers offer special rail-like systems thatmount on the DVD. These allow the drive to be removed from the PC without having to remove screws.

It is designed to optically access data stored on a DVD. A laser moves back and forth near the disksurface and accesses data at a very fast rate.

A 4-pin cable from the power supply plugs into the CDD and provides power to it.Data between the DVD drive and the motherboard is carried on a 40-pin Integrated Drive Electronics

cable.There are two types of DVD drives that typically go into PCs.

DVD-ROM (Read Only Memory) can read DVDs and CDsDVD-RAM (Random Access Memory) units can read and write DVDs. They can also read CDs

A standard DVD stores up to 4.7 Gbytes on one side of the disk. Digitally formatted movies can be storedon a standard DVD in MPEG-2 format.

The main features of the DVD formats include backwards compatibility with current CD media (atleast the newest models of DVD drives), Physical dimensions identical to compact disc with totalthickness equal to 1.2 mm, but with capacity at least 7 times larger than that of CD. Capacities of 4.7 GB,8.54 GB, 9.4 GB, and 17.08 GB, depending on the disk structure.

DVD replication process is similar to that used for compact disks. A disc-based format means fastrandom access like in hard drives and CDs and unlike tapes. Designed from the outset for video, audioand multimedia. Meets the requirement for 133 minutes of high quality video on one side of a disk.

1.3.7 Difference between CD and DVD

The main differences between the CD and DVD are summarized in the following table:Table 1.1 Difference between the CD and DVD

Features DVD CD-ROMSubstrate diameter / thickness (mm) 120 / 1.2 120 / 1.2Sides 1 or 2 1Layers per side 1 or 2 1Capacity (GB) 4.7, 8.54, 9.4, or 17 ~ 0.7Track pitch (microns) 0.74 1.6




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Min pit length (microns) 0.4 - 0.44 0.83Linear velocity used for scan (m/s) 3.5 - 3.84 1.3Laser wavelength (nm) 635 or 650 780Numerical aperture 0.6 0.45Modulation 8 to 16 EFM (8 to 17)Error correction code (ECC) RSPC CIRCDurability and dust/scratch same as that of CD High

1.3.8 Monitor

Often referred to as a monitor when packaged in a separate case, the display is the most-used outputdevice on a computer. The display provides instant feedback by showing you text and graphic images as

you work or play.Displays have come a long way since the blinking green monitors in text-based computer systems of

the 1970s. Just look at the advances made by IBM over the course of a decade:In 1981, IBM introduced the Color Graphics Adapter (CGA), which was capable of renderingfour colors, and had a maximum resolution of 320 pixels horizontally by 200 pixels vertically.IBM introduced the Enhanced Graphics Adapter (EGA) display in 1984. EGA allowed up to 16different colors and increased the resolution to 640x350 pixels, improving the appearance of thedisplay and making it easier to read text.In 1987, IBM introduced the Video Graphics Array (VGA) display system. The VGA standardhas a resolution of 640 x 480 pixels and some VGA monitors are still in use.

IBM introduced the Extended Graphics Array (XGA) display in 1990, offering 800x600 pixelresolution in true color (16.8 million colors) and 1,024 x 768 resolution in 65,536 colors. Mostdesktop displays use liquid crystal display (LCD) or cathode ray tube (CRT) technology, whilenearly all portable computing devices such as laptops incorporate LCD technology. Because of their slimmer design and lower energy consumption, monitors using LCD technology (alsocalled flat panel or flat screen displays) are replacing the venerable CRT on most desktops.

Resolution refers to the number of individual dots of color, known as pixels, contained on a display.Resolution is expressed by identifying the number of pixels on the horizontal axis (rows) and thenumber on the vertical axis (columns), such as 800x600. Resolution is affected by a number of factors,including the size of the screen.

As monitor sizes have increased over the years, display standards and resolutions have changed. Inaddition, some manufacturers offer widescreen displays designed for viewing DVD movies.

Common Display Standards and Resolutions

Resolution Typical Use

1024 x 768 15- and 17-inch CRT monitors15-inch LCD monitors




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1280 x 1024 15- and 17-inch CRT monitors17-and 19-inch LCD monitors1600 x 1200 19-, 20-, 21-inch CRT monitors20-inch LCD monitors2048 x 1536 21-inch and larger CRT monitors1280 x 800 Wide aspect 15.4-inch laptopsLCD displays1680 x 1050 Wide aspect 20-inch LCD monitors1920 x 1200 Wide aspect 22-inch and larger LCD monitors

Two measures describe the size of your display the aspect ratio and the screen size. Historically, computerdisplays, like most televisions, have had an aspect ratio of 4:3. This means that the ratio of the width of the display screen to the height is 4 to 3.

1.3.9 CRT Monitors

A Cathod Ray Tubes (CRT) monitor contains millions of tiny red, green and blue phosphor dots thatglow when struck by an electron beam that travels across the screen to create a visible image. Theillustration below shows how this works inside a CRT. Up until recently, CRTs were the only type of displays for use with desktop PCs. They are relatively big (14" to 16" deep) and heavy (over 15 lbs).

They are available in screen sizes from 14" to 21". A 17" display means that it is 17" measureddiagonally from one corner of the tube to the other. The actual viewing area is smaller than 17" (about16") since the electron gun can’t sweep completely to the tube edge.

CRTs send a stream of electrons at the screen, which is charged to about 25,000 volts. As they strikeit they cause phosphor on the backside of the screen to glow creating light which you see. The electronstream is sweep back and forth and up and down at about 60 sweeps per second and turned off and on at

the right time to make text and graphics images appear.They are powered by standard 120Vac wall power.

Figure 1.12 CRT Monitors

Data is transferred to the display on a cable with a 15-pin D-shell connector that plugs into a connectoron the video card which in turn plugs into one of the PC’s expansion slots.




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1.3.10 LCD Monitors

Liquid Crystal Display (LCD) technology has been used in laptops for some time. It has recently beenmade commercially available as monitors for desktop PCs.

LCDs have no electron gun and are therefore not very deep like CRTs. The text and images you seeare created by a back light behind the panel, that shines through pixels (picture elements). Each pixel ismade up of three chambers red, green and blue. The chambers in each pixel must be opened enough andin the proper proportion to produce the correct brightness and color.

For an LCD to provide a screen resolution 1024 x 768 pixels (SVGA), it must have 786,432 (1024x 768) pixels. In TFT (Thin Film Transistor) type LCDs, each pixel is controlled by a tiny transistor thatopens and closes the chambers in each pixel.Desk top LCD displays are powered by standard 120Vac wall power.

Data is transferred to the display on a cable with a 15-pin connector that plugs into a matingconnector on the video card seated in an expansion slot in the PC.

1.3.11 Difference between LCDs and CRTs

Advantages of LCD Monitors

Smaller and weigh less: An LCD monitor is significantly thinner and lighter than a CRTmonitor, typically weighing less than half as much. In addition, you can mount an LCD on anarm or a wall, which also takes up less desktop space.Require less power: Power consumption varies greatly with different technologies. CRT displaysare somewhat power-hungry, at about 100 watts for a typical 19-inch display. The average isabout 45 watts for a 19-inch LCD display. LCDs also produce less heat.Less eye strain: Because LCD displays turn each pixel off individually, they do not produce aflicker like CRT displays do. In addition, LCD displays do a better job of displaying text comparedwith CRT displays.More adjustable: LCD displays are much more adjustable than CRT displays. With LCDs, youcan adjust the tilt, height, swivel, and orientation from horizontal to vertical mode. As notedpreviously, you can also mount them on the wall or on an arm.

Advantages of CRT Monitors

Multiple resolutions: If you need to change your display’s resolution for different applications, you are better off with a CRT monitor because LCD monitors don’t handle multiple resolutions

as well.More responsive: Historically, CRT monitors have had fewer problems with ghosting and blurringbecause they redrew the screen image faster than LCD monitors. Again, LCD manufacturers areimproving on this with displays that have faster response times than they did in the past.




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Less expensive: Although LCD monitor prices have decreased, comparable CRT displays stillcost less. Better color representation - CRT displays have historically represented colors and

different gradations of color more accurately than LCD displays. However, LCD displays aregaining ground in this area, especially with higher-end models that include color-calibrationtechnology.More rugged: Although they are bigger and heavier than LCD displays, CRT displays are alsoless fragile and harder to damage.

1.3.12 Keyboard

A keyboard’s primary function is to act as an input device rather the keyboard was the first input devicedeveloped for the PC. Using a keyboard, a person can type a document, use keystroke shortcuts, accessmenus, play games and perform a variety of other tasks. Keyboards can have different keys depending onthe manufacturer, the operating system they are designed for, and whether they are attached to adesktop computer or part of a laptop. But for the most part, these keys, also called keycaps, are the samesize and shape from keyboard to keyboard. They’re also placed at a similar distance from one another ina similar pattern, no matter what language or alphabet the keys represent.

Figure 1.13 Keyboard

The standard keyboard layout provides 104 keys organized as four groups:(a) Alphanumeric keys (A-Z, 0-9)(b) Location keys (home, end etc.)(c) Numeric keypad

(d) Function keys (F1-F12)The typing keys include the letters of the alphabet, generally laid out in the same pattern used fortypewriters. According to legend, this layout, known as QWERTY for its first six letters, helped keepmechanical typewriters’ metal arms from colliding and jamming as people typed. Some people questionthis story – whether it’s true or not, the QWERTY pattern had long been a standard by the timecomputer keyboards came around. Keyboards can also use a variety of other typing key arrangements.




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The most widely known is Dvorak, named for its creator, August Dvorak. The Dvorak layout places allof the vowels on the left side of the keyboard and the most common consonants on the right. The most

commonly used letters are all found along the home row. The home row is the main row where you place your fingers when you begin typing. People who prefer the Dvorak layout say it increases their typingspeed and reduces fatigue. Other layouts include ABCDE, XPeRT, QWERTZ and AZERTY. Each isnamed for the first keys in the pattern. The QWERTZ and AZERTY arrangements are commonly usedin Europe. The numeric keypad is a more recent addition to the computer keyboard. As the use of computers in business environments increased, so did the need for speedy data entry. Since a large partof the data was numbers, a set of 17 keys, arranged in the same configuration found on adding machinesand calculators, was added to the keyboard.

In 1986, IBM further extended the basic keyboard with the addition of function and control keys.Applications and operating systems can assign specific commands to the function keys. Control keysprovide cursor and screen control. Four arrow keys arranged in an inverted T formation between thetyping keys and numeric keypad move the cursor on the screen in small increments.Other common control keys include:

HomeEndInsertDeletePage UpPage DownControl (Ctrl)Alternate (Alt)Escape (Esc)

Data is transferred to the PC over a short cable with a circular 6-pin Mini-din connector that plugs intothe back of the motherboard.

There are wireless keyboards that communicate with a pod that is plugged into the keyboard port.Radio Frequency (RF) or InfraRed (IR) technology is used to communicate between the keyboard andthe receiver pod, which plugs into the PC. Cherry Hill Inc. is releasing a keyboard that has an integratedFinger Tip sensor. Instead of having to type in passwords to access the PC a successful fingerprint matchallows entry in to the PC or specific programs.

1.3.13 Mouse

The mouse is the most common ‘pointing device’ used in PCs. Every mouse has two buttons and mosthave one or two scroll wheels. Although originally conceived in the 1960s, a couple of decades passedbefore mice became mainstream.




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Figure 1.14 Mouse

In the beginning, there was no need to point because computers used crude interfaces like teletypemachines or punch cards for data entry. The early text terminals did nothing more than emulate ateletype (using the screen to replace paper), so it was many years before arrow keys were found on mostterminals. Full screen editors were the first things to take real advantage of the cursor keys, and theyoffered humans the first way to point.

Light pens were used on a variety of machines as a pointing device for many years, and graphicstablets, joy sticks and various other devices were also popular in the 1970s. None of these really took off as the pointing device of choice, however.

When the mouse hit the scene — attached to the Mac, it was an immediate success. There issomething about it that is completely natural. Compared to a graphics tablet, mice are extremelyinexpensive and they take up very little desk space. In the PC world, mice took longer to gain ground,

mainly because of a lack of support in the operating system. Once Windows 3.1 made Graphical UserInterfaces (GUIs) a standard, the mouse became the PC-human interface of choice very quicklyBy default the left button is used to select items. The right button is assigned as a context or

alternate menu. A single wheel is normally set to scroll up and down on the active page . If a secondwheel is present, it is usually assigned to scroll left and right on the page.

The button functions can be reassigned by going to Control Panel > Mouse > Buttons tab.Data is transferred to the PC over a short cable with a circular 6-pin Mini-din connector that plugs

into the back of the motherboard.Some versions of the mouse are wireless. They communicate with a receiver pod that is plugs into

the mouse port. Radio Frequency (RF) or InfraRed (IR) technology is used for communication betweenthe mouse and the pod.There are two designs used in a mouse for detecting motion:

Track Ball

This type of mouse uses a rolling (track) ball. As the mouse moves the ball rolls. The rolling motion isconverted electronically into matching movements of the mouse pointer that moves across your videodisplay.




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The track ball mouse is rapidly becoming another casualty of rapidly changing technology. Theoptical mouse has pretty much replaced it. The track ball mouse is already becoming a thing of the past.

Optical Mouse

This mouse uses an InfraRed transmitter/receiver pair to optically detect the motion of the mouse. It hasa number of advantages over the track ball mouse:

No mouse pad is required.Can work on any flat surfaceNo rolling track ball that collects and transfers dirt to the internal rollers, making them slip.When they do, your mouse pointer jumps around in an unpredictable and annoying way!Developed by Agilent Technologies and introduced to the world in late 1999, the optical mouse-actually uses a tiny camera to take thousands of pictures every second.It is able to work on almost any surface without a mouse pad, most optical mice use a small, redlight-emitting diode (LED) that bounces light off that surface onto a complimentary metal-oxide semiconductor (CMOS) sensor.In addition to LEDs, a recent innovation are laser-based optical mice that detect more surfacedetails compared to LED technology. This results in the ability to use a laser-based optical mouseon even more surfaces than an LED mouse.

1.3.14 Audio

Speakers and headphones are the primary audio output devices for a PC.Some monitors have speakers built into their sides. Other speakers are free standing.Passive speakers plug into and are powered directly from the output signal provided by the ‘speaker out’port on the sound card. Active speakers amplify the sound signal from the sound card using battery orrectified AC house power.

Both speakers and headphones are, fundamentally, electrically the same, but there are otherdifferences between the two. Speakers let audio to be broadcasted to people sitting within their range,whether they want to listen or not; headphones keep the audio to one person (well, more or less).Speakers cost more - possibly a lot more - for similar fidelity. Speakers are less portable. They can jiggle

your kidneys with pumping bass; headphones can’t. And headphones can be uncomfortable - thoughgood ones aren’t.

There is more to it than this, though. Headphones can actually mix it with speakers in moredepartments than you might think.

1.3.15 Power Cord

The power cord is the link between the power outlet and the power supply unit in the computer casing.If the power cord is not plugged in, the computer will not power on. It is a good idea to keep the power




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cord plugged into an Uninterruptable Power Supply (UPS), which serves as a surge protector with itsown temporary power source.

1.3.16 Printers

Dot Matrix Printers

Dot matrix printer is a type of printer that produces characters and illustrations by striking pins againstan ink ribbon to print closely spaced dots in the appropriate shape. Dot-matrix printers are relativelyexpensive and do not produce high-quality output. However, they can print to multi-page forms (thatis, carbon copies), something laser and ink-jet printers cannot do. Dot matrix printers are known asimpact printers. Today most dot matrix printers for the home market are extremely inexpensive andhave been mostly superceded by inkjet printers. The biggest draw of dot matrix printers, especially forsome business applications is their ability to print to continuous multi-page forms.

Figure 1.15 Dot matrix printers

Dot-matrix printers vary in two important characteristics:Speed: Given in characters per second (cps), the speed can vary from about 50 to over 500 cps.Most dot-matrix printers offer different speeds depending on the quality of print desired.Print quality: Determined by the number of pins (the mechanisms that print the dots), it canvary from 9 to 24. The best dot-matrix printers (24 pins) can produce near letter-quality type,although you can still see a difference if you look closely.

Inkjet Printer

An inkjet printer is type of printer forms images by spraying tiny droplets of liquid ink onto paper. Small

size and precision placement of the dots of ink produce very near photo-quality images. Ink-jet printersare capable of producing high quality print approaching that produced by laser printers. A typical ink-jet printer provides a resolution of 300 dots per inch, although some newer models offer higherresolutions.

Two primary inkjet technologies are thermal bubble or bubble jet and piezoelectric. The former usesheat and the latter uses a crystal and an electric charge to apply the ink.




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Figure 1.16 Inkjet printers

Some inkjet printers employ a hybrid dye-sublimation process. The color is contained in cartridges,heated, vaporized, and laid down a strip at a time rather a page at a time creating an effect closer tocontinuous tone than traditional inkjet technology. They are also known as bubble jet thermal ink

Laser Printer

Static electricity is the principle behind laser printing which uses a revolving cylinder, a laser beam, finepowder toner, and heat to create images on paper. It’s a type of printer that utilizes a laser beam toproduce an image on a drum. The light of the laser alters the electrical charge on the drum wherever ithits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. Thisis also the way to copy machines work.

Figure 1.17 Laser printers

Black and white lasers (black toner) are relatively inexpensive and common in many homes and smalloffices. Color lasers are typically found in service bureaus and commercial printers and may be used toproduce high-resolution color digital proofs. Adobe PostScript capabilities found in many laser printersmake them popular with graphic designers and desktop publishers who often utilize EPS images and

PostScript files. Hewlett-Packard’s PCL language is another popular command language used by laserprinters

1.4 COMPUTER DATA

To help understand computers in a better way, it is best to first learn about computer data. Computerdata is information required by the computer to be able to operate. It is used to:




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Run programs This is the actual executable program data that the computer will execute to runthe program such as Microsoft Word.

Store program or system configuration information.Store information that the computer user needs such as text files or other files that are associatedwith the program the computer user is running. A common example of a program the computeruser is running is the Microsoft Office suite of products which include Microsoft Word, MicrosoftExcel, and others. These programs are also known as applications.

1.4.1 Data Structure

Computer data is in what is called binary format. This means that it is always a 0 or a 1. It only has thesetwo states and must be in one of them. There are several fundamental data units which include:

Bit: A data unit which must be in one of the two binary states described above. It is the smallestdata unit that exists.Byte: 8 bits of data which has a possible value from 0 to 255.

Word: Two bytes or 16 bits of data with a possible unsigned value from 0 to 16535

1.4.2 Data Transmission

Data transmission is the act of sending data from one place to another. Data is transmitted both insideand outside your computer. There are two fundamental methods of data transmission.

Serial: Data is sent on a single line and one bit is sent at at a time. This is similar to a line whichone item must come one after another.Parallel: Data is sent on more than one line at a time. This may be any number of bits at a time,but is usually one word at a time (two bytes) or possibly three bytes at a time.

1.5 SOFTWARE

Software is a set of instructions that “tell” the hardware to do something. For example, a mixing bowl,a mixer and ingredients are the “hardware” and the recipe is the “software” or directions that allow youto do something with the hardware.

Figure 1.18




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The term software describes the programs that run on your system. This includes your computer operatingsystem and other computer programs which run. Software is written in a computer language (such as

Basic, C, Java, or others) by programmers. The computer language is in a text format and can be read bya person although if you do not understand the structure and rules of the language you may not understandit very well. Once a program is written, an operation is performed on it which is called compiling.Compiling is the process of changing the textual written language into a binary language which can beunderstood by the computer.

Writing these text files and converting them to computer readable files is the way operating systemsand most application programs are created.

Software includes application software, which are programs that allow you to perform a specific tasksuch as word process, browse the Internet, or edit pictures and system software, which are programs thatcontrol and monitor all input and output and processing activities of the computer such as the operating

system and utility programs1.6 NETWORK

The word network can be used to describe a very large and complicated set of equipment. A networkconsists of two or more computers that are linked in order to share resources (such as printers and CD-ROMs), exchange files, or allow electronic communications. The computers on a network may be linkedthrough cables, telephone lines, radio waves, satellites, or infrared light beams In its most accurate andsimplest definition a network refers to the cables and electronic components that amplify the signals goingthrough the cables. The amplifying equipment is necessary to ensure accurate communication and makethe signal stronger if it needs to go long distances. Broader definition is when many people talk about anetwork, they are talking about a network using a very broad concept. For instance if someone cannot getto their email, they may say, “the network is down”. Likewise they may say this if they cannot surf theInternet or get to their files. They may not stop to think that in each specific instance there is a single pieceof equipment that may provide the capability, which they are trying to use.

Most people who work on a corporate or organizational network think about the network incomponent parts. The three main parts are:

The cabling and amplifiersThe workstations, which most members of the organization use to access resources.Higher-powered computers called servers - These are the machines that provide what networkadministrators call services. Services include the functions that most people try to use such asemail, reading and writing files, printing, and getting to the Internet. Whenever a user is tryingto do something on the network, there is a service or machine providing the capability to do so.This even includes times when someone is trying to get to network resources from their home.

1.6.1 Types of Network

The three basic types of networks include:




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(a) Local Area Network (LAN)(b) Metropolitan Area Network (MAN)(c) Wide Area Network (WAN)

Local Area Network (LAN)

A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generallylimited to a geographic area such as a writing lab, school, or building. Rarely LAN computers are morethan a mile apart.

In a typical LAN configuration, one computer is designated as the file server. It stores all of thesoftware that controls the network, as well as the software that can be shared by the computers attachedto the network. Computers connected to the file server are called workstations. The workstations canbe less powerful than the file server, and they may have additional software on their hard drives. On

most LANs, cables are used to connect the network interface cards in each computer. Metropolitan Area Network (MAN)

Metropolitan Area Network (MAN) span bigger area than LAN and generally confined to cities.

Wide Area Network(WAN)

Wide Area Networks (WANs) connect larger geographic areas, one part of the world to the other.Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of network.

A WAN is complicated. It uses multiplexers to connect local and metropolitan networks to globalcommunications networks like the Internet. To users, however, a WAN will not appear to be much

different than a LAN or a MAN1.6.2 Protocol

A protocol is a set of rules that governs the communications between computers on a network. Theserules include guidelines that regulate the following characteristics of a network: access method, allowedphysical topologies, types of cabling, and speed of data transfer.The most common protocols are:(a) Ethernet: The Ethernet protocol is by far the most widely used. Ethernet uses an access method

called CSMA/CD (Carrier Sense Multiple Access/Collision Detection). This is a system whereeach computer listens to the cable before sending anything through the network. The Ethernet

protocol allows for linear bus, star, or tree topologies. Data can be transmitted over wirelessaccess points, twisted pair, coaxial, or fiber optic cable at a speed of 10 Mbps up to 1000 Mbps.(b) Fast Ethernet: To allow for an increased speed of transmission, the Ethernet protocol has

developed a new standard that supports 100 Mbps. This is commonly called Fast Ethernet. FastEthernet requires the use of different, more expensive network concentrators/hubs and networkinterface cards. In addition, category 5 twisted pair or fiber optic cable is necessary. Fast Ethernetis becoming common in schools that have been recently wired.




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(c) Local Talk: LocalTalk is a network protocol that was developed by Apple Computer, Inc. forMacintosh computers. The method used by LocalTalk is called CSMA/CA (Carrier Sense

Multiple Access with Collision Avoidance). The LocalTalk protocol allows for linear bus, star,or tree topologies using twisted pair cable. A primary disadvantage of LocalTalk is speed. Itsspeed of transmission is only 230 Kbps.

(d) Token Ring: IBM developed the Token Ring protocol in the mid-1980s. The access methodused involves token passing. In Token Ring, the computers are connected so that the signaltravels around the network from one computer to another in a logical ring. The Token Ringprotocol requires a star-wired ring using twisted pair or fiber optic cable. It can operate attransmission speeds of 4 Mbps or 16 Mbps. Due to the increasing popularity of Ethernet, the useof Token Ring in school environments has decreased.

(e) FDDI: Fiber Distributed Data Interface (FDDI) is a network protocol that is used primarily to

interconnect two or more local area networks, often over large distances. The access methodused by FDDI involves token-passing. FDDI uses a dual ring physical topology. Transmissionnormally occurs on one of the rings; however, if a break occurs, the system keeps informationmoving by automatically using portions of the second ring to create a new complete ring. Amajor advantage of FDDI is speed. It operates over fiber optic cable at 100 Mbps.

(f) ATM: Asynchronous Transfer Mode (ATM) is a network protocol that transmits data at a speedof 155 Mbps and higher. ATM works by transmitting all data in small packets of a fixed size;whereas, other protocols transfer variable length packets. ATM supports a variety of media suchas video, CD-quality audio, and imaging. ATM employs a star topology, which can work withfiber optic as well as twisted pair cable. ATM is most often used to interconnect two or morelocal area networks. It is also frequently used by Internet Service Providers to utilize high-speedaccess to the Internet for their clients. As ATM technology becomes more cost-effective, it willprovide another solution for constructing faster local area networks.

1.6.3 Topology

The physical topology of a network refers to the configuration of cables, computers, and other peripherals.Physical topology should not be confused with logical topology which is the method used to passinformation between workstations

Main Types of Physical Topologies

Linear Bus: A linear bus topology consists of a main run of cable with a terminator at each end.

All nodes (file server, workstations, and peripherals) are connected to the linear cable. It is easyto connect a computer or peripheral to a linear bus and requires less cable length than a startopology. But its main disadvantage is that entire network shuts down if there is a break in themain cable.




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Figure 1.19 Linear Bus topology

Star: A star topology is designed with each node (file server, workstations and peripherals)connected directly to a central network hub or concentrator. Data on a star network passesthrough the hub or concentrator before continuing to its destination. The advantage of a StarTopology is that it is easy to install and wire and no disruptions to the network then connectingor removing devices. But it is more expensive than linear bus topologies because of the cost of the concentrators and requires more cable length than a linear topology. If the hub or concentratorfails, nodes attached are disabled

Concentrator/Hub

Nodes

Figure 1.20 Star topology




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Star-Wired Ring: A star-wired ring topology may appear (externally) to be the same as a startopology. Internally, the MAU (multistation access unit) of a star-wired ring contains wiring

that allows information to pass from one device to another in a circle or ring. The Token Ringprotocol uses a star-wired ring topology.Tree: A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable . Tree topologiesallow for the expansion of an existing network, and enable schools to configure a network tomeet their needs. It’s advantage is that it is supported by several hardware and software venders

Nodes

Nodes

Backbone Cable

Concentrator(Hub)

Figure 1.21 Tree topology




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1.7 INTERNET: DEFINITION

The word internet is used to describe a network of networks which incorporate a very large and complicatedset of equipment. To understand the internet, there are three areas of discussion which are very helpful.These include the various services provided across the internet, the functions that enable the internetto work, and the various organizations that are part of the internet.

1.7.1 Internet Services

The main services used on the internet include:(a) Web browsing: Supported by the HTTP protocol, this functions allows users to view web pages

using a web browser.(b) E-mail: Allows people to send and receive electronic messages.(c) Other lesser used services: These include telnet (allows remote login to computers), FTP (Allows

quick file transmission to remote computers), and gopher (An early form of text based form of reading internet documents which is rarely used today).

1.7.2 Types of Internet Access

Before you can connect to the Internet, you need to determine the type of Internet access you would like,and which Internet Service Provider (ISP) you want to provide you with this access. An ISP is thecompany that provides you with your connection to the Internet for a fee. Often ISPs offer differenttypes and tiers of access, so it is a good idea to consider the common types of service before exploring

specific companies.Dial-up Access

Dial-up access is usually the least expensive way to access the Internet; however, it is also the slowest.With dial-up service, you need a phone line and PC modem to dial-up and be connected to the Internetby your ISP. A modem ties up the phone line so can’t use the phone and computer at the same time.

While dial-up access can be an affordable option, the web pages load slowly due to the limitations of the modem. Some websites with a lot of videos or graphics may have a difficult time loading, if they loadat all. Additionally, with dial-up access, your Internet connection isn’t immediate. Since you have to usethe telephone line to dial into a server, it can take from several seconds to minutes before you can access

the Internet.If you only use the Internet to check your email and occasionally view other websites, a dial-up

connection may serve your needs. If you are going to spend any significant amount of time online, youshould consider another option. Keep in mind that some ISPs have increased the fee for dial-up accessin an effort to transition more people to broadband access.




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Digital Subscriber Line Access

Digital Subscriber Line (DSL), provides high-speed, Internet access through a phone line. With DSLservice, you can talk on the telephone and access the Internet at the same time. It is considered a type of broadband Internet access, which refers to high-speed Internet connections that allow for transmissionof data at rates 10 to 50 times faster than dial-up service.

A DSL modem and an Ethernet card are required for installation. A splitter may also be required tofilter the DSL signal from the low frequency voice signal

Cable Access

Cable access is provided through your local TV cable company and transferred through your TV cables.Like DSL access, it is considered broadband, high-speed Internet access. If you don’t have cable TV, youcan still purchase cable Internet service as long as it is available in your area.

With cable access, web pages load quickly and you will find it easy to download and upload files. Onething to be aware of though is that cable access is a shared service and can be affected by others who usethe same cable lines. For example, if it is a holiday and everyone in your neighborhood is at home surfingthe web, you may notice that some aspects of service are slower than normal. In most areas, this won’t bean issue.

Satellite Access

Satellite access can be used in locations where there is no broadband cable or DSL Internet available.Satellite access is available across the world and can provide you with a broadband connection that isequal to a high speed connection. LTS is the most expensive and will require costs such as installation

and satellite equipment, which will cost several hundred dollars.1.7.3 Internet Service Provider (ISP)

Once you have decided which type of Internet access you are interested in, you can determine whichISPs are available in your area that offer the type of Internet access you want. Then, you need to choosethe ISP that best meets your needs based on their prices and service packages, and secure Internet accessthrough that company. Talk to friends, family members, and neighbors to see what ISP they use.Some things to consider as you research ISPs:

SpeedPrice

Installation SoftwarePhysical ServiceService RecordExtras such as email accounts and web spaceTechnical Support




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Remote AccessContract Terms

1.7.4 Internet Browser

A browser is the tool that allows you to view and interact on the Internet. Once you have an accountwith an ISP and can access the Internet, you’ll need to use a browser to access web pages. Browsers can bereferred to the window of the web because they allow you to view all the pages on the Internet.

Most computers come preloaded with Microsoft Internet Explorer, so you do not have to worryabout purchasing a browser; however, you do not have to use Internet Explorer. If you would prefer to tryanother browser option, you can. For example, Mozilla Firefox is a free browser that you can downloadand use.

1.8 COMPUTING RESOURCES

Computing is usually defined as the activity of using and developing computer technology, computerhardware and software. It is the computer-specific part of information technology. Computer science(or computing science) is the study and the science of the theoretical foundations of information andcomputation and their implementation and application in computer systems. There are loads of computing resources available. Evaluating and selecting software packages that meet an organization’srequirements is a difficult software engineering process. Selection of a wrong software package can turnout to be costly and adversely affect business processes. There are a number of methodologies for selectingsoftware packages, software evaluation techniques, software evaluation criteria, and systems that supportdecision makers in evaluating software packages. Evaluation of the software packages includes analytichierarchy process. There is lack of a common list of generic software evaluation criteria and its meaning.A framework for finding a proper computing resource includes software selection methodology evaluationtechnique, evaluation criteria, and system to assist decision makers in software selection.

1.8.1 Applications

Applications are programs that you as the user use to perform specific tasks. These are the applicationsthat most users are familiar with such as Word 2000, Excel 2000, and Netscape Communicator. Here aresome examples of applications.There are listed as below:(a) Word Processing: Enables users to create, edit, format and edit textual documents such as letters

Example Microsoft Word 2003, Corel Word Perfect, Lotus Word Pro(b) Spreadsheet: Enables users to manipulate a table of data usually making numerical and business

calculations and projections.For example Microsoft Excel 2003, Lotus 1-2-3, Corel Quattro Pro

(c) Database: Enables the user to create and maintain a database in which data is organized for easeof use and manipulation.For example Microsoft Access 2003, Microsoft Visual FoxPro, Lotus Approach




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(d) Presentation Graphics: Enables users to create images for group presentations, self-runningslide shows and for other situations that require the presentation of organized, visual information.

For example Microsoft PowerPoint 2003, Lotus Freelance Graphics, Corel Presentations(e) Web Browsers: Enables users to view web pages and allows for communication on the Internet.

For example Microsoft Internet Explorer, Mozilla(f) Photo-Editing: Enables users to edit, crop, manipulate photos that were scanned in or imported

from a digital camera.For example Adobe Photoshop, PhotoImpact, Microsoft PictureIt

1.8.2 System Software

System software refers to the files and programs that make up your computer’s operating system. Systemfiles include - libraries of functions, system services, drivers for printers and other hardware, systempreferences, and other configuration files. The programs that are part of the system software includeassemblers, compilers, file management tools, system utilites, and debuggers. Since system software runsat the most basic level of your computer, it is called “low-level” software. It generates the user interfaceand allows the operating system to interact with the hardware. Fortunately, you don’t have to worryabout what the system software is doing since it just runs in the background.

System Software Categories

There are different categories of system software namely:(a) Operating system(b) Compiler(c) Loaders(d) Linkers(e) Interpreter(f) Assembler(g) Utility programs.

Operating System

The operating system is the nucleus of all software activity. It is the most important program that runson a computer. Every general-purpose computer must have an operating system to run other programs.

It is the first program loaded into memory when the computer is turned on and, in a sense, brings life tothe computer hardware. Without it, you cannot use your word processing software, spreadsheet software,or any other applications. It is the ultimate source of communication with computer. When you give thecomputer a command, the operating system relays the instructions to the ‘brain’ of the computer, calledthe microprocessor or CPU. You cannot speak directly to the CPU because it only understands machinelanguage. When you are working in an application software program, such as Microsoft Word, commands




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that you give the application are sent through the operating system to the CPU. Windows2000,Window95/98, Mac OS, Unix and DOS are all examples of operating systems.

Operating System Tasks:

Operating systems perform basic tasks, such as, Recognizing input from the keyboard, Sending output tothe display screen, Keeping track of files and directories on the disk, Controlling peripheral devices suchas disk drives and printers.

Application

Disk Drive

MouseMonitor

Keyboard Printer

OperatingSystem

Figure 1.22

Compiler

A compiler is a computer program (or set of programs) that transforms source code written in a computerlanguage (the source language) into another computer language (the target language, often having abinary form known as object code). The most common reason for wanting to transform source code is tocreate an executable program.




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The name “compiler” is primarily used for programs that translate source code from a high-levelprogramming language to a lower level language (e.g., assembly language or machine code). A program

that translates from a low level language to a higher level one is a decompiler. A program that translatesbetween high-level languages is usually called a language translator, source-to-source translator, orlanguage converter.

Loader

In computing, a loader is the part of an operating system that is responsible for loading programs fromexecutables (i.e., executable files) into memory, preparing them for execution and then executing them.

The loader is usually a part of the operating system’s kernel and usually loaded at system boot timeand stays in memory until the system is rebooted, shut down, or powered off. Some operating systemsthat have a pageable kernel may have the loader in the pageable part of memory and thus the loadersometimes may be swapped out of memory.

Linker

In computing, a linker or link editor is a program that takes one or more objects generated by a compilerand combine them into a single executable program.In IBM mainframe environments such as OS/360 this program is known as a linkage editor.

Interpreter

Interpreter translates interactively each programming statement into an immediately usable machine

language instruction. Although an interpreter slows down the execution speed of a program somewhat,it does not require extra steps to compile and link like a compiler.

In a production environment where throughput is more critical, a compiled language is preferred.Any high-level language can either be interpreted or compiled

Assembler

Assembler is a program that translates programs from assembly language to machine language.

Utility Programs

Utility programs help manage, maintain and control computer resources. These programs are availableto help you with the day-to-day chores associated with personal computing and to keep your systemrunning at peak performance.

Some examples of utility programs include:Virus scanning software, Backup software, Scandisk andDisk defragmenter




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Virus Scanning Software

Virus Scanning Software are utility programs designed to protect your computer from computer viruses.Virus scanning software is critical to uses, due to the number of computer viruses (small computerprograms created to disrupt and destroy computer files and/or operating system software).

Virus scanning software scans your disk each time you insert it into a computer. Virus scanningsoftware needs to be updated on a regular basis Updates insure that your virus scanning software willprotect you from the most recent viruses. Virus scanning packages come with directions on how toreceive updates to your software!

Backup software is software that assists you in backing up your files and even the entire computerhard drive. It is important for you to back up your files regularly. If you own your own computer, youshould think about how to backup your valuable data on your hard drive.

Scandisk

Scandisk is a utility provided with Windows computers. Scandisk scans your disks to see if there are anypotential problems on the disk, such as bad disk areas. Since disks are magnetic media, all disks, including your hard drive can be corrupted.

Freeware

The term freeeware is commonly used for copyrighted software given away free by its author. It isavailable for free but the author retains the copyright, which means that a user does not have the rightto modify anything in the software that ,is not explicitly allowed: by the developer. Thus, freewaresoftware permits re-distribution but not modification. Freeware usually carries a license that permitsredistribution but may have other restrictions, such as limitations on its commercial use.Freeware is an umbrella term that covers:(a) Donationware : The authors of donationwareask that anyone using their software make a donation

to the authors or to some third party such as a charity.(b) Postcardware : It is freeware (no-charge software that is freely shared) that requires only that the

user send the software provider a postcard as a form of payment.(c) Abandonware : It is commercial software that has not been sold for a long time or whose copyright

holder is defunct; it has been abandoned. The licenses of most such software forbid redistributionor require payment; so distributing it violates the author’s copyright (even if the author does notor cannot enforce it).

(d) Adware : It is distributed as freeware, but it requires the user to view advertisements to use thesoftware.

Shareware

Shareware is the software, which comes with permission for people to redistribute copies for a limitedperiod. Anyone who continues to use a copy is required to pay a license fee. Therefore, a free use of the




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software is usually limited to a period. It is distributed without payment ahead of time as is common forproprietary software. Typically shareware software is obtained free of charge by downloading, thus allowing

one to try out the program ahead of time. It is accompanied by a request for payment, and often paymentis required as per the terms of the license past a set period. For example, software is distributed with a 30days trial period like WinZip software.

Commercial Software

Commercial software represents the majority of software purchased from software publishers. Thissoftware comes in pre-packaged, is available in software stores, and can be obtained through Internet.It_is developed by business organisations, which aims to earn profits from its use. It is always copyrighted.The licensing restrictions vary somewhat from vendor-to-vendor and product-to-product, and changefrequently. It is generally more expensive than competing shareware products for example MicrosoftWindows.

Open Source Software

Open source software is created by generous programmers and released into the public domain for pubicuse. The underlying programming code is available to the users so that they-may read it, make changesto it, and build new versions of the software incorporating their changes for software. Usually thesesoftware are distributed under an open-source license - General Public License (GPL). Such a licenserequires that the source code should be distributed along with the software, and that the source code isfreely modifiable, with least restrictions, such as the requirement to preserve the author’s names andcopyright statement in the code. The Linux operating system is an example of open source software.

Proprietary Software

In general, proprietary describes a technology or product that is owned exclusively by a single companythat carefully guards knowledge about the technology or the. Product’s internal working. Some proprietaryproducts can only function properly, if at all, when used with other products owned by the same company.Example of a proprietary product is Adobe Acrobat, whose Portable Document Format (PDF) files canonly be read with Acrobat Reader: Proprietary software is also called as Closed Source Software,(CSS).Its use, redistribution or modification is prohibited or is restricted so much that the user effectivelycannot use it freely.

Firmware

Firmware is a combination of software; permanently stored in .the memory. As the name suggests,firmware is a program or data that has been written onto read only memory (ROM). For example, theBIOS (which is installed inside a computer on a chip) checks different parts of the system before loadingthe operating system into memory. Being firmware, it ensures that it will always be available and will notbe damaged in case of a power failure. ROMs, PROMs, and EPROMs that have data or programs recordedon them are firmware




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EXERCISE

Descriptive Type Questions1. Discuss the characteristics of computers.2. What are the advantages of transistors over vacuum tubes?3. Discuss the various types of computers in detail.4. List out the various applications of computers5. Explain how read/write operation is carried out in optical disk.6. Discuss advantages and disadvantages of:

(a) Magnetic disks (b) Optical disks

7. Distinguish between the following:(a) Sequential mode and Random mode (b) Static RAM and Dynamic RAM(c) Magnetic tape and Magnetic disk

8. What is a speech recognition system? Explain its types and give logical reasons. Why do currentlyavailable speech recognition devices have limited success?

9. What do you mean by optical scanning devices? Explain any four such devices.10. Explain the different types of printers. Make a clear difference between them in terms

of speed, cost, and method of operation, aiJ suggest suitable applications.11. What do you understand by software? Discuss its types.12. Explain the difference between hardware and software with their definition and uses.13. Explain the concept of software installation and uninstallation.14. How is software update different from software upgrade? Explain.15. What is software piracy and how can it be avoided?16. Discuss the various computer generations along with the key characteristics of the computers of

each generation.17. Discuss the basic organization of a computer system, and explain the functions of various units

of a computer system.18. What are the types of memories available in the computer system? How are they organized in the

hierarchy?19. What is ROM? Differentiate between EPROM and EEPROM.20. With the help of diagrams, explain how RAM, ROM, and CPU interact with each other.21. Explain the working of a magnetic tape. What are its advantages and disadvantages?22. What are the advantages and disadvantages of using a pseudocode?23. Discuss the three basic program control structures with suitable examples.




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24. Explain the features of a good programming language.25. Describe the classification of programming languages.26. Write short notes on the following: (a) Compiler27. What are mass storage devices? How are they useful in storing large amount of data?28. Describe the application areas where plotters are useful. Discuss the various types of plotters.29. What is speech synthesizer? How does it function? Give some of its typical applications.30. What is LCD? Differentiate between CRT and LCD monitors.31. Write short notes on the following:

(a) Resolution (b) Aspect ratio(c) Dot pitch (d) Refresh rate(e) Colour depth

32. Why are input and output devices necessary for a computer system?33. What are pointing devices? Discuss some of the commonly used pointing devices.34. What is a touch screen device? Explain with their advantages and disadvantages and give some

typical applications for which touch screen is most suitable as an input device.35. Explain program development cycle with the help of a block diagram.36. Define an algorithm. List the characteristics of a good algorithm. 3: Define a flowchart. List

some important reasons for using flowcharts.

Fill in the Blanks

1. Laptops are also known as …………………………2. Computers can be classified as …………, …………….., and……………3. The invention of logarithms influenced the development of ……………….4. PDA stands for ………………………………5. CPU consists of ………………, ……………….., and ……………….6. Physical components on which the data is stored permanently are called ...…………..7. The two types of data access methods available with secondary storage devices are.............................

and ………………………….8. The time required to position the read/write head over the desired track is called

....………………………9. WORM stands for …………………………..10. The multiple association of disk array box used for obtaining high performance, large capacity,

and reliability is called as …………………….11. The basic component of first generation computer was ……………………




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12. The speed of computer is calculated in ………………………………13. Third generation computers were ……………….…… based machines.14. Keyboard is an ………………………. device.15. MICR stands for ………………….16. The bar-coded data represent the ………………….. and a device, which is used for reading the

barcoded data, is known as ………………………17. The most used layout of a keyboard is ……………………..18. The printed form of output is referred as …………………….and the form of outputs which is

shown on a display screen, is referred as ……………….19. An impact printer, which gives only alphanumeric output, is called as ……...20. …………….. plotters are computer graphics devices that use drum or flat-bed paper holder.

21. A non-impact printer that forms an image by spraying ink from a matrix of tiny jets is called…………………

22. The mouse may be classified as ……………… or ………………..23. ………………… refers to the electronic storage place for instructions and data in the computer

system.24. The time period lagged between a request made and the action being performed is called

..........................25. The memory that requires constant refreshing circuit to preserve the information is called

..........................

26. …………………………… memory is used as a backup for storing data that are not currentlyused by the processor. Mouse and light pens are examples of ………………… input devices.27. ……………… is a machine-readable code in the form of parallel vertical lines.28. ……………………… is the oldest printing technology.29. The quality of the monitor is generally judged by considering four basic terms ...........

………………………, ……………………….., and …………………………30. The number of bits used to describe a pixel is known as ……………………31. A computer can talk to persons through a device known as …………………..32. ……………… is the set of coded instruction that brings the machinery to life.

33. Software is often divided into two major categories, namely, …………...... and …………………………34. A ……………. acts like a translator between the device and programs that use the device.35. The functions of an operating system that allows creation, deletion, suspension, resumption,

scheduling, and synchronisation of processes is called .............................36. ………………… software scans the hard disk for viruses and removes them.




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37. …………. helps in converting programming language into machine language.38. …………….. is the process of copying software from CD-ROM (or floppy disks) to the hard disk

and configuring it to work with the computer hardware.39. The sequence of instructions that instruct the computer to carry out a specific task is

……………………..40. The tools that act as a mediator in the process of translating real life problem into a computer

program are …………….., ……………….., and ………………..41. A program that translates the assembly language code into machine language code is

…………………………42. The part of operating system that brings an executable file residing on disk into memory and

start running is ………………………43. Compiler and interpreter are also called as ………………………44. The two-part forms of machine language instructions are …………………, ..................

……………………. and ……………………..45. …………….. is the unauthorised copying of an organisation’s internally developed software or

the illegal duplication of commercially available software.46. ………………. is the software, which comes with permission for people to redistribute copies

for a limited period.47. Firmware is the program or data that has been written onto48. ………………………. language is very close to the hardware.49. COBOL, FORTRAN, and C are examples of ……………………….

True/False Questions

1. A terabyte comprises 1024 megabyte.2. The ROM chip, which can be rewritten several times and requires the action of ultraviolet

radiations to erase its contents, is EPROM.3. The memory which is utmost accessible to the processor is hard disk.4. CD-ROM is a kind of magneto-optical disk.5. Rotational delay time is also known as latency.6. Auxiliary memory stores information about BIOS and start-up routines.

7. The memory that resides inside the processor is called processor memory8. LSI and VLSI technology are part of fifth generation computers.9. A laptop is a portable computer.10. Primary memory and main memory are synonyms.




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11 . The ability of a computer to understand and respond to commands that are given in a naturallanguage, such as English, is known as artificial language processing.

12. PARAM is an example of portable computer13. DVD-ROM and CD-ROM has the same storing capacity.14. The speed of memory depends upon the access time of data that is stored.15. Operating system is application software.16. A device driver allows another program to interact with a hardware device.17. Data recovery is the process of retrieving deleted or inaccessible data from failed electronic

storage media.18. Anti-virus is the software to protect computer from the bacteria.19. Installation files usually have the extension .EXE or .Z1P.

20. Software update and software upgrade perform the same function.21. Software piracy is the authorised copying of an organisation’s internally developed software.22. Public domain software refers to any program that is not copyrighted.23. Firmware software is embedded in the hardware devices.24. Microsoft Word is an image editing software25. Floppy disk can be write-protected.26. ALU carries out all the calculations in the CPU.27. Micro computers are more powerful than mini computers.28. Laptop is also known as notebook.29. Vacuum tubes were a part of third generation computers.30. DVAC was a second generation computer.31. The generic way of describing an algorithm without the use of programming is known as program.32. The keyword, DETERMINE, used in a pseudocode is an input operation.33. The terminal symbol in a flowchart represents start of program logic.34. Programming is the art and science of creating computer programs.35. A program that links several object modules and libraries to form a single, coherent program is

linker.36. The language translator that translates the programs written in high-level language into its

corresponding machine code is assembler.37. Any hardware item that is attached to the CPU is referred to as peripheral device.38. Impact printers are slower as compared to non-impact ‘printers.39. The speed of a printer is measured by character per minute.40. Audio response is a soft copy output.




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41. Dot pitch can be changed by the user.42. Plotters are best suited for desktop publishing.43. Bank cheques are an example of bar code marking.44. QWERTY is the most popular keyboard layout.45. A speech recognition system converts the computer text and commands into human spoken

words.46. More pixels per square inch means better resolution.47. The graphical representation of an algorithm is called flowchart.48. Machine language is also called as low-level language.49. Pseudocode can be compiled by a program compiler.50 The diamond shape symbol in the flowchart signifies processing51. A digital camera’s photographs can be stored in a computer’s hard disc.52. The most common aspect ratio used in computer monitors is 4:4.53. Raster scan monitors draw a picture one line at a time and for this reason they are referred as

vector displays, stroke-writing or calligraphic displays.54. Ultrasonic acoustic waves are one of the most commonly used touch screen techniques.55. 16-bits colour allows up to 256 colours.

Multiple Choice Questions

1. .............................. is a very small computer that can be held in the palm of the hand.

(a) PDA (b) PC(c) Laptop (d) Mini computer

2. Choose the odd one out.(a) Micro computer (b) Mini computer(c) Super computer (d) Digital computer

3. The development of computers can be divided into generations.(a) 3 (b) 4(c) 5 (d) 6

4. A spiral shape track formatting is present in:(a) Floppy Disk (b) Optical Disk(c) Hard Disk (d) Half-inch Tape Cartridge

5. UNIVAC is an example of:(a) First generation computer (b) Second generation computer(c) Third generation computer (d) Fourth generation computer




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6. The computer that is not considered as a portable computer is:(a) Laptop computer (b) Notebook computer(c) Mini computer (d) None of these

7. CPU stands for:(a) Central Protection Unit (b) Central Processing Unit(c) Central Power Unit (d) Central Prerogative Unit

8. Select the smallest memory size.(a) Terabyte (b) Gigabyte(c) Kilobyte (d) Megabyte

9. The access time refers to:(a) Time required locating and retrieving stored data(b) Time required to locate the lost data(c) Time required to delete specific data on a certain memory location(d) None of the above

10. FPI stands for:(a) Faults per inch (b) Frames per inch(c) Figure per inch (d) Film per inch

11. In which kind of disk does the read/write head physically touches the surface?(a) Hard Disk (b) Compact Disk

(c) Floppy Disk (d) None of these12. A floppy can be write protected by:

(a) Breaking the slider(b) Positioning the slider to cover the hole(c) Positioning the slider away from the hole(d) Cannot be write protected

13. Analytical Engine was developed by:(a) Gottfried Wilhem Von Leibriz (b) Charles Babbage(c) Herman Hollerith (d) Joseph-Marie Jacquard

14. The main distinguishing feature of fifth generation computers will be:(a) Liberal use of microprocessors (b) Artificial Intelligence(c) Extremely low cost (d) Versatility

15. The unit that performs the arithmetical and logical operations on the stored numbers is knownas …………….




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(a) Arithmetic Logic Unit (b) Control Unit(c) Memory Unit (d) Both (a) and (b)

16. The …………… is the “administrative” section of the computer system.(a) Input Unit (b) Output Unit(c) Memory Unit (d) Central Processing Unit

17. The type of memory that uses in-circuit wiring to erase the content by applying electric field is:(a) PROM (b) Flash Memory(c) EAROM (d) EEPROM

18. The storage device that has high cost per bit of storage:(a) SDRAM (b) Cache Memory(c) Read Only Memory (d) Hard Disk

19. The secondary storage device that follows the sequential mode of access:(a) Optical Disk (b) Magnetic Disk(c) Magnetic Tape (d) None of these

20. ……………… is the most commonly used input device.(a) Keyboard (b) Mouse(c) Joystick (d) Scanner

21. Mouse, trackball, and joystick are the examples of (a) Scanning devices (b) Storing devices

(c) Pointing devices (d) Multimedia devices22. Which of the following is not a computer terminal?

(a) Intelligent (b) Smart(c) Both (a) and (b) (d) None of these

23. Which of the following technique is best suited for bank cheques?(a) OCR (b) OMR (c) BAR (d) MICR

24. Choose the most suitable device among the following for playing computer games.(a) Hand-held scanner (b) Joystick

(c) Optical Mark Reader (d) Digital Camera25. Light pen is frequently used in

(a) Computer Aided Design (b) Word Processing(c) Presentation (d) Spreadsheet

26. Choose the odd one out.




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(a) QWERTY (b) SULTRY(c) AZERTY (d) DVORAK

27. Which of the following is not a pointing device?(a) Scanner (b) Trackball(c) Light Pen (d) Mouse

28. Which of the following is not an output device?(a) Printer (b) Keyboard(c) Monitor (d) Plotter

29. Which of the following is used for both input and output?(a) Computer Terminals (b) Pen Plotter(c) Dot Matrix Printer (d) None of these

30. The …………….. is also called as letter quality printer.(a) Dot Matrix Printer (b) Ink Jet Printer(c) Daisy Wheel Printer (d) Laser Printer

31. An individual small dot, which one sees on the computer screen is called as ...............(a) Font (b) Character(c) Screen Point (d) Pixel

32. LCD stands for(a) Liquid Colour Display (b) Light Colour Display

(c) Lithium Crystal Display (d) Liquid Crystal Display33. With the combinations of ……………….., ..........................., and colours, other colours can be

shown.(a) Red, Black, Blue (b) Yellow, Blue, Green(c) Red, Blue, Green (d) Black, White, Yellow

34. Which of the following is system software?(a) Microsoft Word (b) Adobe Photoshop(c) Microsoft PowerPoint (d) Windows 98

35. ……………. analyses and executes each line of source code in succession, without looking at the

entire program.(a) Compiler (b) Operating System(c) Interpreter (d) Device Drivers

36. The assembly language program must be translated into machine code by a separate programcalled




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(a) Assembler (b) Interpreter(c) Compiler (d) Loader

37. If you change Windows 98 operating system to Windows XP, you are actually performing………………………..(a) Update (b) Upgrade(c) Patch (d) None of these

38. Which of the following is application software?(a) Database Management System (b) Image Editor(c) Spreadsheets (d) All of these

39. Linux is a type of ……………….. software.(a) Shareware (b) Open Source(c) Commercial (d) Proprietary

40. Which of the following was a disadvantage of the first generation language?(a) Machine dependency (b) Less efficient(c) Need for more disk space (d) All of these

41. Good programming language has the following features:(a) Portable, Safe (b) Reliable, Good Performance(c) High Cost (d) Only (a) and (b)

42. Query languages comes under:

(a) Third Generation (b) Fourth Generation(c) Fifth Generation (d) None of these43. Which of the following program control structure allows the program to make a choice bettseen

two alternate paths depending upon the condition?(a) Sequence (b) Loop(c) Selection (d) None of these

44. Choose the odd one out:(a) Abstraction (b) Encapsulation(c) Inheritance (d) Linking

45. Flow lines in a flowchart are used to connect:(a) Two Terminals (b) Two Connectors(c) Two Input/Output (d) All of these

46. Programming tools helps in:(a) Producing readable code (b) Making the program logic easier(c) Reducing the size of programs (d) None of these




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47. A high-level language is. a programming language that is:(a) Easier to use(b) Considered a first generation language(c) Considered a third generation language(d) Both (a) and (c)

48. What consists of instructions written as string of 1s and Os?(a) Query Language (b) Assembly Language(c) Machine Language (d) None of these

ANSWERS:

Fill in the Blanks1. Notebooks 2. Desktop, laptop, Workstation/server3. Punched cards 4. Personal Digital Assistant5. Control Unit, ALU, Memory Unit 6. Secondary Storage Devices7. Sequential Access, Random Access 8. Seek time9. Write Once Read Many 10. RAID11. Vacuum Tubes 12. MIPS13. IC 14. Input15. Magnetic Ink Character Recognition 16. Information, bar code reader17. QWERTY 18. Hard copy, Soft Copy19. Daisy wheel printer 20. Drum21. Ink Jet Printer 22. Mechanical mouse, optical mouse23. Memory 24. Response time25. Dynamic Ram 26. Secondary27. Bar code 28. Impact printing29. Size, color, resolution, aspect ratio 30. Resolution31. Speaker 32. program

33. System software, application software 34. Operating system35. Scheduling 36. Antivirus37. Translators 38. installation39. Program 40. Editor, compiler, linker41. Assembler 42. loader




43. translators 44. operation code, address45. piracy 46. open source47. memory 48. machine49. high level languages

True/False Questions

1. F 2. T 3. F 4. T 5. T 6. F7. T 8. F 9. T 10. T 11. T 12. F13. F 14. F 15. F 16. T 17. T 18. F19. T 20. T 21. F 22. T 23. T 24. F25. T 26. T 27. F 28. T 29. F 30. T31. F 32. F 33. T 34. T 35. T 36. F37. T 38. T 39. T 40. T 41. F 42. F43. F 44. T 45. F 46. T 47. T 48. T49. F 50. F 51. T 52. F 53. T 54. F55. T

Multiple Choice Questions

1 a 2 d 3 c 4 b 5 a 6 c7 b 8 c 9 a 10 b 11 c 12 b13 b 14 b 15 a 16 d 17 d 18 b19 c 20 a 21 c 22 d 23 d 24 b

25 a 26 b 27 a 28 b 29 a 30 c31 d 32 d 33 c 34 d 35 c 36 a37 b 38 d 39 b 40 d 41 d 42 b43 c 44 d 45 d 46 a 47 d 48 c

it infrastructure 2

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