Computer for IBPS

8/10/2019 Computer for IBPS

1/61

Computer HistoryComputer through the Ages

We give below an overview of the developments which have taken place upto the time when 1stGeneration computers came into existence. These are milestones which played some role later on

towards our achievements in the present day computer age.

Year Inventor Invention

16 th Century China Abacus. This is considered as the first babystep towards computers

1617 Johan Napier Napiers Bones

1642 Blaise Pascal First Calculating Machine

1671 Gottfried Von Leibntiz Calculator (Modified Pascals machine)

1801 Joseph Jacquard Card of holes for weaving patterns

1823-34 Charles Babbage Difference Engine and Analytical Engine

1880 Herman Hollerith Lady AdaLovelace Tabulating machine using punch

cards Binary number System

1930 Howard Aitken and Grace Hopper(IBM) MARK-1

1937-38 Dr John Vircent Atanassoff ABC (Atanassoff-Berry-Computer)

1946 JP Eckert and JW Mauchly ENIAC (Electronic Numerical and Calculator)

1940s H Goldshine, AW Burks and JohanVon Neumann Stored Program Concept


2/61

1947-49 Johan Von Neumann EDSAC (Electronic Delayed StorageAutomatic Computer)

1950 Moor School in USA EDVAC (Electronic Discrete VariableAutomatic Computer)

1951 Eckert and JW Mauchly UNIVAC-1 (Universal Automatic Computer)

Computer Fundamentals of ComputerBinary System Bit vs Byte

What is Binary System : A system in which information can beexpressed by combinations of the digits 0 and 1. The modern day origin of this can betraced to late 1930s, when Claude Shannon showed that it was possible to carry outlogical operations by assigning the number 1 to true and 0 to false while using switcheswhich were closed for true and open for false,.

What is Bit? Or What is Bits ? : The term bitor bits means binary digit , meaning 0 or 1 in binary numbering. . Thus, we can saythat it is the smallest unit of information which can be manipulated by a digital machine.(While writing in short form we merely use a lowercase b to represent bits ). With two bits,you can have four different states (2*2):

0 0 0 0

0 1 0 1

1 0 1 0

1 1 1 1

With 3 bits, you can have eight different states (2*2*2), and so on. Thus, for a group of nbits, it is possible to represent 2 n values.


3/61

What is Byte? : The byte is a unit of information composed of 8 bits. It canbe used to store, among other things, a character, such as a letter or number. (Whilewriting in short form we merely use an uppercase B to represent a byte ).

For a byte, the smallest number possible is 0 (represented by eight zeroes, 00000000), andthe largest is 255 (represented by eight ones, 11111111), making for 256 different possiblevalues.

The data and instructions (code) that a CPU uses are coded into bytes. For example, capitalletter A in ASCII (PC) code is byte 0100 0001. A lower case a is byte 0110 0001.

A 16-bit unit of information is usually called a word.

A 32-bit unit of information is called a double word (sometimes called a dword ).

Tips :

Bit Vs Byte :

A bit is always represented by a small b, a Byte is always represented by a largeB.

It has become common practice to use bits in reference to interface speeds and bytes inreference to memory and storage capacities.

Kilobytes and Megabytes :

Till 1998 , the following system for presenting various values was prevalent(Some softwares still use the following system)

One kilobyte (kB) = 2 10 bytes = 1024 bytes


4/61

One megabyte (MB) = 2 20 bytes = 1024 kB = 1,048,576 bytes

One gigabyte (GB) = 2 30 bytes = 1024 MB = 1,073,741,824 bytes

One terabyte (TB) = 2 40 bytes = 1024 GB = 1,099,511,627,776 bytes

However, in December 1998, , the International Electro technical Commission weighed in onthe issue and issued new guidelines which are known as IECs standardised units.

One kilobyte (kB) = 1000 bytes

One megabyte (MB) = 1000 kB = 1,000,000 bytes

One gigabyte (GB) = 1000 MB = 1,000,000,000 bytes

One terabyte (TB) = 1000 GB = 1,000,000,000,000 bytes

The earlier system of representing bytes hasbeen redefined by IEC and is known as binary kilo (kibi), binary mega(mebi), binary giga (gibi), and binary tera (tebi). They are defined as:

One kibibyte (kiB) is worth 2 10 = 1024 bytes

One mebibyte (MiB) is worth 2 20 = 1,048,576 bytes

One gibibyte (GiB) is worth 2 30 = 1,073,741,824 bytes

One tebibyte (TiB) is worth 2 40 = 1,099,511,627,776 bytes

Computer Basic operations and

TerminologiesComputer Overview Basic Concepts


5/61

What is a computer ? Define a Computer ?

A computer is an electronic device, which can compute and process data as per theprogrammed set inside it. However, these days the term is mostly used to refer to the

Desktop and Laptop computers that are used by most of us. If you have seen inside a

computer, you must have noticed that it is not a single part machine. These machines(Desktop and laptops) are also popularly known as Personal Computers or PC. Eachcomputer consists of number of technical parts which are assembled in the requiredmanner.

Broad Categories of Computers :-

1.Based on Uses :

1.1 Analog Computer : It measures pressure, temperature, length, etc, of physicalquantities and converts into its numerical values. They are mainly used for scientificand engineering purposes.

1.2 Digital Computer : It is used in counting of numbers, words or other specialsymbols. It is also used in fuel control of automobiles and banking processes.

1.3 Hybrid Computer : It is the combined form of analog and digitalcomputer. Information is continuously converted into data that are received in theform of input. Output may be in form of analog and digital. They are used in factoriesand machines.

2. Based on Sizes : computers are also classified based on their size viz :

2.1 Micro Computer : It is the smallest computer in which ALU and CPU are basedon the same chip.

2.2 Personal Computer : It is single user system used generally in homes andsmall businesses. Desktop and Laptops are examples of PCs, as these are best forday to day small operations.

2.3 Mini Computer : It is more powerful than micro computer and can be used bymany users at the same time. It processes data very fast.

2.4 Main Frame Computer : They are giant in size and of highly storage capacity.They can process an ample amount of data very rapidly. They are used in banks,large organization and public sectors.

2.5 Super Computer : They are capable of processing the huge amount of data infraction of seconds. They are used in very complex calculation.

What are the Major Parts of the Computer :-


6/61

Central Processing Unit (popularly known as CPU) it consists of different technicalparts like processor, motherboard, hard disc, RAM, CD Drive and cabinet with SMPS.

Monitor Keyboard Mouse

What are major accessories of the computer system ?

In addition to the above referred major components of the computer, we find the followingaccessories attached to most of the computers :-

Speakers Printers Scanners Modem

Explain the concept of CPU:

Central Processing Unit or CPU is considered as the brain of computer. CPU consists ofelectronic circuits that interpret and execute instructions. It communicates with the input,output and storage devices. CPU, with the help of memory, executes instructions in therepetition of machine cycles. The speed of computer is measured in megahertz, MHz. AMHz is a million machine cycles per second. A personal computer of 500 MHz has aprocessor capable of handling 500 million machine cycles per second. Another measure ofspeed is gigahertz (GHz), which means a billion machine cycles per second.

Explain the concept of Memory RAM / ROM :

Memory or internal memory or primary storage works with the CPU to hold instructions anddata in order to be processed. It is in the memory that data and instructions are placedafter being input.

(a) Moreover, the information is also placed in memory after processing so as to bereturned to an output device. This kind of memory holds data only temporarily till electricalcurrent flow continuously. If current is interrupted, data is lost. Random Access memory(popularly known as RAM) is an example of this kind of memory. Thus, in this memory

when we switch off the computer, the data is lost. The users access data in RAM memoryrandomly as per needs. RAM can be erased or written over at will by the computerprogramme

(b) Another kind of memory is Read Only Memory (ROM). It contains prorams and datathat are permanently recorded when the computer is manufactured. It is read only and is


7/61

used by the processor. It is permanent in nature. and can not be altered or deleted by theuser.

Thus, we can say that RAM is like a slate where you can write something for immediatereference and then wipe / change data by adding or deleting when it is not needed, but

ROM is like a printed book, where once the text is printed then it cannot be altered.

(c) Secondary memory is also known as external memory or storage. It consists of HardDiscs, Floppy Disc (now a days out of fashion) , CDs and DVDs as well as pendrives. External device consists of more storage space and most dynamic in terms ofstoring data.

Memory is measured in bytes. A byte is usually made up of 8 bits and represents onecharacter a letter, digit or symbol. The number of bytes that can be held is a measure ofthe memory and storage capacity. Bytes are usually measured in groups of kilobytes,

megabytes, gigabytes and terabytes.

What are the Functions of the major components / accessories of the computesystem:-

CPU is the main unit of processing data, a mother borad is an electronic circuit for differentfunctions, hard disc is for storing the data, CD drive is to read and write data on CDs(compact discs). Monitor is for displaying the data, and is also popularly known as screenor display unit. Keyboard is used to input the data. Mouse is a pointing or selection


8/61

unit. Speakers, we all know, are used to hear the sound / music. Printer is used to takethe print of the data from the computer system. Scanner is used to scan and then store theimage / pictures in the computer. Modem is used to connect to internet.

File Extensions and RulesFile Extensions

File extensions are an important part of the name of a file. Most of the software open a filewith a fixed name of file extensions. In case file extension is changed arbitrarily, the filemay not open in the desired software and / or may termed as corrupted and thus data maybe lost forever, if the user does not know how to set the same right. Let us first understandbasic concepts about Folders, Files and their extensions :-

What are Files / Folders / Directories :

Let us now learn about certain basic operations we need to do whenever we work on acomputer. Suppose, we have created some document i.e. we have typed some document,then at the end of it, we would like the same to be saved for future reference or take printout. In order to save a new document or file, you must first choose the Save command.Most modern software place this command in a menu which you can access with the mousebutton or Alt key. When one such document is saved it is called a file. While saving thedocument, it will ask you about the name you wish to give to this new document. Alongwithgiving a name to this file, the user has a choice to decide as to where such a file should besaved. Such files can be saved within a Folder or Directory. Thus while giving a new nameto the file, users must also choose a directory and/or disk to store the file in. Some softwareprograms will automatically save files in specific directory that is created when the programis installed (default settings).

Modern software place this command in a menu which you can access with the mousebutton or Alt key. When one such document is saved it is called a file. While saving thedocument, it will ask you about the name you wish to give to this new document. Alongwithgiving a name to this file, the user has a choice to decide as to where such a file should besaved. Such files can be saved within a Folder or Directory. Thus while giving a new nameto the file, users must also choose a directory and/or disk to store the file in. Some software

programs will automatically save files in specific directory that is created when the programis installed (default settings).

Thus, a folder or directory can hold any number of files.

Sometimes, we install new software on our computer. In such cases also, the setupexecutable file automatically creates new directories / folders and stores all the softwarefiles in such newly created folders / directories.


9/61

Thus, we can say that user can create and delete directories or folders as the need arises.Older operating systems require that the directory be emptied of files before it can bedeleted. When deleting / removing a directory, user must always check that no importantfiles is left in such directory or sub-directory. You should delete the directory only afterensuring that it doesnt contain files you still need.

You can easily move files from one folder or directory to another, through either the usemenu commands or drag & drop using the mouse or a file utility

On the disk (it can be your hard disk, our floppy disc, CD or Pen Drive) you can create anynumber of directories / folders each of such directories / folders can contain number offiles. Moreover, These directories or folders could be compared to a filing cabinet. All filesare stored in a directory / folder. Most hard disks have many directories or folders and filescan be stored in any of them.

Directories can have sub-directories and sub-sub-directories many levels down. Thedirectory immediately below the current directory is called the child directory. The directoryimmediately above the current one is called the parent directory. The top of the directorystructure is called the root directory.

Some common rules are:

All files are saved on a disk or storage device.

A disk is usually broken up into directories and sometimes into partitions.

A directory or folder is a way of keeping like files in a common area.

Rules for File Names and Extension

Computers using DOS 6.X or older followed the 8.3 rule i.e. a filename can only be 1 to 8characters long followed by a 1 to 3 character extension separated by a dot. Threecharacter extensions are common because of this.

Modern operating systems allow computer users to use filenames up to 256 characters. Macusers, Windows 9X & NT/2000 and UNIX/LINUX (along with a few other) use long file namesbut names using over 32 characters get unwieldy. It is better to use a directory or folder tohelp describe them and keep common files together with shorter filenames.

Many modern software programs (applications) add their own extension to filenames. Theseextensions allow operating systems to recognize certain filenames and associate (match)them to the program that created it.


10/61

File Types, Appropriate Extensions And Software Used to Open Such Files

Type of File xtension Used By Which Software

D Image Files 3dm hino 3D Model

D Image Files 3dmf uickDraw 3D Metafile

udio Files aac dvanced Audio Coding File

udio Files aif udio Interchange File Format

udio Files iff nterchange File Format

udio Files m3u edia Playlist File

udio Files mid IDI File

udio Files midi IDI File

udio Files mp3 P3 Audio File

udio Files mpa PEG Audio File

udio Files ra eal Audio File

udio Files ram eal Audio Media


11/61

udio Files wav AVE Audio File

udio Files wma indows Media Audio File

ackup Files bak ackup File

ackup Files gho orton Ghost Backup File

ackup Files old ackup File

ackup Files ori riginal File

ackup Files tmp emporary File

ompressed Files deb ebian Software Package

ompressed Files gz nu Zipped File

ompressed Files pkg ac OS X Installer Package

ompressed Files rar inRAR Compressed Archive

ompressed Files sea elf-Extracting Archive

ompressed Files sit tuffit Archive

ompressed Files sitx tuffit X Archive


12/61

ompressed Files zip ipped File

ata Files 123 otus 1-2-3 Spreadsheet

ata Files csv omma Separated Values File

ata Files dat ata File

ata Files db atabase File

ata Files dll ynamic Link Library

ata Files mdb icrosoft Access Database

ata Files pps owerPoint Slide Show

ata Files ppt owerPoint Presentation

ata Files sql tructured Query Language Data

ata Files wks icrosoft Works Spreadsheet

ata Files xls icrosoft Excel Spreadsheet

ata Files xml ML File

eveloper Files c /C++ Source Code File

eveloper Files cpp ++ Source Code File


13/61

eveloper Files java ava Source Code File

eveloper Files pl erl Script

isk Files dmg ac OS X Disk Image

isk Files iso isc Image File

isk Files toast oast Disc Image

isk Files vcd irtual CD

ncoded Files bin acbinary II Encoded File

ncoded Files hqx inHex 4.0 Encoded File

ncoded Files mim ulti-Purpose Internet Mail Message

ncoded Files uue uencoded File

xecutable Files app ac OS X Application

xecutable Files bat OS Batch File

xecutable Files cgi ommon Gateway Interface Script

xecutable Files com OS Command File


14/61

xecutable Files exe indows Executable File

xecutable Files pif rogram Information File

xecutable Files vb BScript File

xecutable Files ws indows Script

ont Files fnt ont File

ont Files fon eneric Font File

ont Files otf penType Font

ont Files ttf rueType Font

ame Files gam aved Game File

ame Files nes intendo (NES) ROM File

ame Files rom 64 Game ROM File

ame Files sav aved Game

raphical Interchange Formatile ai dobe Illustrator File

raphical Interchange Formatile drw rawing File


15/61

raphical Interchange Formatile

dxf rawing Exchange Format File

raphical Interchange Formatile eps ncapsulated PostScript File

raphical Interchange Formatile jpeg PEG Image File

raphical Interchange Formatile jpg PEG Image File

raphical Interchange Formatile png ortable Network Graphic

raphical Interchange Formatile ps ostScript File

raphical Interchange Format

ile psd hotoshop Document

raphical Interchange Formatile psp aint Shop Pro Image File

raphical Interchange Formatile svg calable Vector Graphics File

raphical Interchange Formatile tif agged Image File

mage Files mng ultiple Network Graphic


16/61

mage Files pct icture File

isc Files msi indows Installer Package

isc Files torrent itTorrent File

isc Files yps ahoo! Messenger Data File

age Layout Files indd dobe InDesign File

age Layout Files pdf ortable Document Format File

age Layout Files qxd uarkXpress Document

age Layout Files qxp uarkXpress Project File

lugin Files 8bi hotoshop Plug-in

lugin Files plugin ac OS X Application Plug-in

lugin Files xll xcel Add-In File

aster Image Files bmp itmap Image File

aster Image Files gif raphical Interchange Format File

ettings Files cfg onfiguration File


17/61

ettings Files ini indows Initialization File

ettings Files reg egistration Information

ystem Files cab indows Cabinet File

ystem Files cpl indows Control Panel

ystem Files cur indows Cursor

ystem Files dmp indows Memory Dump

ystem Files drv evice Driver

ystem Files key ecurity Key

ystem Files lnk ile Shortcut

ystem Files sys indows System File

ext Files doc icrosoft Word Document

ext Files log og File

ext Files msg ail Message

ext Files rtf ich Text Format File

ext Files txt lain Text File


18/61

ext Files wpd ordPerfect Document

ext Files wps icrosoft Works Word Processor Document

ideo Files 3gp GPP Multimedia File

ideo Files asf dvanced Systems Format File

ideo Files asx icrosoft ASF Redirector File

ideo Files avi udio Video Interleave File

ideo Files mov pple QuickTime Movie

ideo Files mp4 PEG-4 Video File

ideo Files mpg PEG Video File

ideo Files qt pple QuickTime Movie

ideo Files rm eal Media File

ideo Files swf acromedia Flash Movie

ideo Files wmv indows Media Video File

eb Files asp ctive Server Page


19/61

eb Files css ascading Style Sheet

eb Files htm ypertext Markup Language File

eb Files html ypertext Markup Language File

eb Files js avaScript File

eb Files jsp ava Server Page

eb Files php ypertext Preprocessor File

eb Files xhtml xtensible Hypertext Markup Language File

Home Computer Awareness Computer Hardware Parts of the Personal Computer

Computer Hardware Parts of the PersonalComputer

Computer Hardware

by

Rajesh Goyal

The Major Parts of the Computer :-

Central Processing Unit (popularly known as CPU) it consists of different technicalparts like processor, motherboard, hard disc, RAM, CD Drive and cabinet withSMPS.

Monitor / Screen Keyboard Mouse
http://www.bestguru.com/http://www.bestguru.com/http://www.bestguru.com/computer-awareness/http://www.bestguru.com/computer-awareness/http://www.bestguru.com/computer-awareness/http://www.bestguru.com/wp-content/uploads/2013/10/Rajesh-Goyal-allbankingsolutions.jpghttp://www.bestguru.com/computer-awareness/http://www.bestguru.com/


20/61

The major accessories of the computer system ?

. In addition to the above referred major components of the computer, we find the followingaccessories attached to most of the computers :-

Speakers Printers Scanners Modem Microphone

Various Hardware Components of A Personal Computer :

PC Case : It consists of a thin sheet metal enclosure that housesthe motherboard, power supply and various drives (HDD, FDD, CD,DVD). These cases come in two shapes / styles desktop andtower. Now a days the tower type is predominant. It stands upright and ismuch taller than it is wide. It is usually placed on the floor near the desk orunder the top of the desk. On the other hand desktop version is pizza boxprofile and usually placed on the desktop.

Motherboard : The motherboard is the main circuit board in a

PC. It contains all the circuits and components that run the PC. MajorComponents found on the motherboard are:

1. CPU - Full form of CPU is Central Processing Unit or commonly known asprocessor. CPU consists of electronic circuits that interpret and executeinstructions. It communicates with the input, output and storage devices. CPU,with the help of memory, executes instructions in the repetition of machinecycles. It is the brain of every PC. We can say that the CPU is the hardware devicein a computer that executes all of the instructions from the software. Allscheduling, computation and control occurs here.


21/61

1. There are two major makers of CPUs namely Intel and AMD. We often hear that CPUis Intel Pentium or Celeron. Currently the Pentium chip or processor, made byIntel, is the most common CPU though there are many other companies thatproduce processors for personal computers. like CPU made by Motorola andAMD. The speed of a microprocessor is measured in megahertz, or cycles persecond. A MHz is a million machine cycles per second. A personal computer of500 MHz has a processor capable of handling 500 million machine cycles persecond. Another measure of speed is gigahertz (GHz), which means a billionmachine cycles per second.

BIOS Full form of BIOS is Basic Input Output System. It is a non-volatilememory that contains configuration information about the PC. It contains all thecode required for the CPU to communicate with the keyboard, mouse video display,disk drives and communications devices.

When a PC is powered on it uses the BIOS boot code to set up many required functionsthat bring the PC to a point where it is ready to work.

RTC Full form is Real Time Clock. This chip keeps date, day and time in a24 hour format just like our watch. The PC uses this clock to time stamp files asthese are created and / or modified.

Chip Set - these are large chip(s) that integrate many functions thatused to be found in separate smaller chips on the motherboard. They save spaceand cost.

The functions performed by these chip sets often broken into two devices with one providingan interface from the CPU to the memory and the other providing controllers for IDE, ISA,PCI and USB devices (see below).

In addition to above, in a PC, you will notice a number of connectors on themother board.

(a)Primary Connectors : Some of such primary connectors are :

(b)Power - A 20 pin connector accepts a plug from the power supply.This plug carry DC power to all the circuits on the motherboard.


22/61

Keyboard - A Mini-din 6-pin (round) connector found at the back of themotherboard is where the keyboard plugs in.

(d) Mouse - A Mini-din 6-pin connector found next to the keyboardconnector is where the where the mouse plugs in.

(e) Display - This connector is not integrated into the motherboard but isincluded in this list since its function is absolutely necessary. It is a 15-pin, D-shell typeconnector found on a video card that plugs into the AGP connector of the motherboard (seebelow).

(f) IDE - stands for Integrated Drive Electronics. These are 40 pinconnectors that provide a place to connect the ribbon cables from the drives (hard and

CD/DVD). All data between the motherboard and the drives is carried in these cables. Theyare not accessible unless the PC cover is removed.

(g) FDD connector - it is similar in function to the IDE connector.It is a 34 pin ribbon connector that carries data between the motherboard and any floppydrive installed in the PC. Not accessible with PC cover on.

(h) DRAM - Dynamic Random Access Memory connectors for SIMM andDIMM type memory modules. Not accessible with chassis cover on.

PORTS or Connectors enable us to connect external output or inputdevices to our computer. The basic types of ports are: Parallel ports can be used to connectprinters, zip drives, video capture (such as Snappy), external hard drives, or digitalcameras. Serial ports that are frequently u sed to connect all of the above exceptprinters. In addition, there are some serial port mice. PS2 ports are used to connect sometypes of mice. There are also places on your computer to attach a keyboard and s-videocable.


23/61

(A)Serial Connectors

o Standard Serial Connector - This connector has been aroundin PCs since they first appeared. It was originally located on ISA expansion type cards (see

below). Today it is an integral part of newer motherboards. It is a 9- pin, D-shell connectorthat allows you to connect external devices with serial ports to your PC. The maximum datarate is 115 KB/s.

o USB Universal Serial Bus This is a relatively new serial bus.Originally specified as low speed, 1.2 Mb/s, it was enhanced to full speed, 12Mb/s. Thelatest version 2.0 is specified as high speed, 400 MB/s.

Someday USB will completely replace the standard serial connector that has been theworkhorse serial port in earlier PCs. USB is now a standard connector on all newmotherboards. Unlike serial and parallel ports, the USB port is designed to powerdevices connected to it. The devices must be low power devices and must be able toreduce their current draw to less than 0.5uAmps when commanded to do so by the PC.

(B)Parallel Connectors

o Centronix or Standard Parallel - This connector hasbeen around in PCs since they first appeared. It has 37-pins and is now integrated on newmotherboards. It is usually used to connect your printer to the PC and moves data at about1MB/s.

o SCSI - Small Computer System Interface moves data at a maximum of up to 80Mb/s. Itnot integrated into most PC motherboards. It can be added to a PC as an Expansion card(see below). Some printers and hard disk drives use SCSI interfaces.

Expansion Card Connectors - The CPU connects to expansioncard connectors through one of the chip set ICs mentioned above. They are located on themotherboard near the rear of the PC. These connectors allow special function cards to pluginto and work with the PC.

Before motherboards integrated the serial and centronix connectors they were found onexpansion boards that plugged into ISA slots.


24/61

Most PCs have the following expansion connector types:

o ISA - Industry Standard Architecture connectors have been around since 1980 andfirst appeared in the IBM XT PC. This type of slot still appears on some newer motherboards

so that older expansion boards can still be used. However, many motherboards no longerhave ISA connectors on them.

o PCI - Peripheral Component Interconnect is a newer and faster interface thataccepts all expansion cards that have a PCI interface.

o AGP - Accelerated Graphics Port is a connector that is designed to work with videocards. Your video display plugs into and is controlled by one of these video cards. Manymodern video cards offer enhanced 3D-graphics and fast, full motion video.

1. Power Supply : A power supply is installed in the back corner ofthe PC case, next to the motherboard. It converts 120 / 240 vac (standard housepower) into DC voltages that are used by other components in the PC. A 20conductor cable carries +5vdc, -5vdc +12vdc, -12vdc and ground to themotherboard.

1. MOUSE : A mouse is an acronym for Manually Oscillating Utensil SonicallyEngaged. It is the electronic finger of the computer. One type of mouse has a roundball under the bottom of the mouse that rolls and turns two wheels which controlthe direction of the pointer on the screen. Another type of mouse uses an opticalsystem to track the movement of the mouse. Laptop computers use touch pads,buttons and other devices to control the pointer. Hand helds use a combination ofdevices to control the pointer, including touch screens

It is used to point at items in the window environment. The mouse arrow indicates yourposition on screen. It can change its shape depending upon your position on screen or theprogram you were using. In a word processor the mouse will appear as a flashingcursor or insertion point. Moving and clicking the mouse can move the cursor onscreen.The mouse has 2 buttons. The left button is used to send signals to programs. The rightmouse button gives the user various menus. By double clicking the left mouse button,programs can be opened. A new mouse, the Intellimouse, allows the user to scroll a screenin a program using a center wheel.


25/61

5. MONITOR The monitor is the computers screen or display. Monitors come insizes from 14 inch, 17 inch, to as large as 36 inch monitor. The resolution of the monitor

determines the sharpness of the screen. The resolution can be adjusted to control thesc reens display. The monitor shows information on the screen when you type. This iscalled outputting information.

When the computer needs more information it will display a message on the screen, usuallythrough a dialog box ..

Most desktop computers use a monitor with a cathode tube or liquid crystal display .Most notebooks use a liquid crystal display monitor. To get the full benefit of todayssoftware with full colour graphics and animation, computers need a color monitor with adisplay or graphics cards

6. KEYBOARD : The keyboard has keys similar to our old typewriter but Italso has some additional keys. The keyboard is used to type information into the computeror input information.

There are many different keyboard layouts and sizes with the most common for Latin basedlanguages being the QWERTY layout (named for the first 6 keys).

Function keys are found at the top of the keyboard. These control programsand are labeled F1 to F12. F1 always provides help in windows environment.

Cursor control keys are arrows that allow you to move the cursor in fourdirections (up, down, right, left).


26/61

Numeric keys are found on the right side of the keyboard and act much like acalculator pad, however, key must be pressed on in order for these keys to function.

ESC or the escape key allows you to exit or escape some programs.

/ Front slash key is used in web addresses on the Internet.

\ Back slash key signals a sub-directory.

Page up and page down keys allow you to move up or down ina document.

Shift key and caps lock key change the case of the letter whenpressed.

ALT key moves the cursor to the menu bar, which is useful in the event the mouseis not functioning.

Pause key pauses text on screen in DOS.

ALT + Ctrl + Delete keys reboots or restarts the computer when they are pushed in thatsequence. This is called a warm boot. A cold boot simply means turning the computer off fora minute and then turning it back on. These boots are necessary if a program fails tofunction.

Backspace key erases errors when the mouse is placed after the error.

Delete key erases errors when the mouse is placed before the error.


27/61

7.Printers - The printer takes the information on your screen and transfers it topaper or a hard copy . There are many different types of printers with various levels ofquality. The three basic types of printer are; dot matrix , inkjet , and laser .

Dot matrix printers work like a typewriter transferring ink from a ribbon to paperwith a series or matrix of tiny pins.

Ink jet printers work like dot matrix printers but fires a stream of ink from acartridge directly onto the paper.

Laser printers use the same technology as a photocopier using heat to transfer toneronto paper.

8.Scanners - Scanners allow you to transfer pictures and photographs to yourcomputer. A scanner scans the image from the top to the bottom, one line at a time andtransfers it to the computer as a series of bits or a bitmap. You can then take that imageand use it in a paint program, send it out as a fax or print it. With optional OpticalCharacter Recognition (OCR) software you can convert printed documents such asnewspaper articles to text that can be used in your word processor. Most scannersuse TWAIN software that makes the scanner accessible by other software applications.

A Raster Image Processor (RIP) is a component used in a printing system whichproduces a raster image also known as a bitmap. The bitmap is then sent to a printingdevice for output. The input may be a page description in a high-level page descriptionlanguage such as PostScript, Portable Document Format, XPS or another bitmap of higher orlower resolution than the output device. In the latter case, the RIP applies either smoothingor interpolation algorithms to the input bitmap to generate the output bitmap.

9.Digital cameras allow you to take digital photographs. The images arestored on a memory chip or disk that can be transferred to your computer. Some camerascan also capture sound and video.

Computer Input Devices and Output Devices


28/61

Difference between Input Devices and OutputDevices

Input devices are those parts of the computer which accept data in a form that can be

utilized by the computer. Thus input devices help us in feeding the data into the computersystem. Output devices are those parts which show us the data we desired to extract fromthe computer. The examples of input / output are :-

A) Input Devices: A1 : Hand Operated Input Devices

Keyboard and Mouse are the most commonly used hand operated input devices.

Some of the hand operated input devices along with keyboard and mouse are as follow:

Track Ball : It is used as an alternate of mouse.and has to move its ballin order to utilize it that causes the pointer to move on the screen.

Joystick : It is very popular among the people fond of computer games, buttoday different types of game controllers are replacing them gradually. Joystick is used tocontrol the machine such as crane in the process of building constructions.

Digital Camera : Digital camera can take the image and alsorecords the videos. The images and videos taken by digital cameras are recorded in files.These files can get copied into the computer that can be further edited for many purposes.

Microphone : Microphone is used to input the sound. It can be used toenter text in any word processing application with voice recognition software in thecomputer.

Touch Screen : There is a network of light rays in touch sensitivevisual display unit or in screen that recognizes the touch. Touch screen is used in manymobile phones. They are often used in cash machines and chopping centres.

Video Digital : Video digital takes the images from video camera ortelevision and stores it into the computer for further use. The video sequences taken byvideo digital are mainly used in multimedia presentation.


29/61

Scanner : Scanner is used to convert an image into its digital form. It issimilar to photocopier but it makes digital copy of an image instead of its hard copy. It isused to scan the text with the software optical character recognition.

Graphic Tablet : There is a flat pad on the graphic tablet uponwhich an user writes with the help of a special pen. Pictures can also be drawn on thescreen using that pen in this way.

B) Output Devices :

The means through which computer gives output are known as Output Devices. Someof the most popular output devices are as follow:

1. Monitor2. Printer3. Projector4. Sound Card5. Speaker6. Video Card

Projector Projector is that hardware device which projects an image on the flat surface like computerscreen. These devices are generally used in meetings, seminars and presentations becauseeach person can easily see the image projected by it sitting in a big room.

Sound Card

It is also known as Sound Board or Audio Card. Sound card is an expansion card or unifiedcircuit that enables computer to produce sound through speaker or headphone

Speaker

It is the device which presents the sound produced during any programme. This isconnected to sound card and gives the sound produced by card in the form of output.

Video Card


30/61

It is also known as Graphics Card, Video Board or Video Controller. This is an internal circuitboard that allows the image displaying devices like monitor to display the images.

Integrated Input and Output Devices :Modem is a connector and is used both as input and output device. Thus, modem is bothan input device and an output device. Similarly, we can say the latest touch screen displayunits also act as input and output devices simultaneously, as we can send instructions tocomputer by merely touching the screen and then results are also displayed on the samescreen.

MODEM : Full form of modem is MOdulator and DEModulator . The modem is aconverter of analog to digital and digital to analog. Thus, we can say that a modem is amechanical means of translating computer information or retrieving information from theInternet via a phone line. It needs communication software in order to work and can beattached internally or externally. Internet transmission can also take place over anISDN line or the even faster T1 line. No modem is necessary for these types of transmissionbut you will need an ISDN adapter. Modems are measured by the speed that theinformation is transferred. The measuring tool is called the baud rate . Originally modemsworked at speeds below 2400 baud but today analog speeds of 56,000 are standard. Cable,wireless or digital subscriber lines can transfer information much faster with rates of300,000 baud and up.

The details of the functions performed by each of the hardware are given in thehardware section.

Computer Memory in Computers and Disks /Drives

Different Types of Computer Memory

What is RAM ? The full form of RAM is Random Access Memory). This is also knownas main memory. Computers can write and read data from RAM. This is in contrast toROM which permits you only to read data. However, most RAM is volatile, which meansthat it requires a steady flow of electricity to maintain its contents. As soon as the power isturned off, whatever data was in RAM is lost. The users access data in RAM memoryrandomly as per needs. RAM can be erased or written over at will by the computerprogramme
http://www.webopedia.com/TERM/R/RAM.htmlhttp://www.webopedia.com/TERM/R/RAM.html


31/61

What is ROM ? The full form of ROM is Read only Memory): Computers almostalways contain a small amount of read-only memory, commonly known as ROM. This

memory holds instructions for starting up the computer. As name indicates you can onlyread from this memory and cannot write anything on it. Moreover, it is non-volatile innature i.e. even when power is switched off, the memory is not lost.

Thus, we can say that RAM is like a slate where you can write something for immediatereference and then wipe / change data by adding or deleting when it is not needed, butROM is like a printed book, where once the text is printed then it cannot be altered.

PROM : The full form of PROM is Programmable Read- Only Memory. A PROM is amemory chip on which you can store a programme. But once the PROM has been used,you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile.

EPROM (erasable programmable read-only memory): An EPROM is a special type ofPROM that can be erased by exposing it to ultraviolet light.

EEPROM (electrically erasable programmable read-only memory): An EEPROM is aspecial type of PROM that can be erased by exposing it to an electrical charge.

Memory is measured in bytes. A byte is usually made up of 8 bits and represents onecharacter a letter, digit or symbol. The number of bytes that can be held is a measure of

the memory and storage capacity. Bytes are usually measured in groups of kilobytes,megabytes, gigabytes and terabytes.

Disk Drives

Secondary memory is also known as external memory or storage. It consists of HardDiscs, Floppy Disc (now a days out of fashion) , CDs and DVDs as well as pendrives. External device consists of more storage space and most dynamic in terms ofstoring data.

The disk drive determines the path by which you send and receive information to thecomputer. Information stored on a disk is measured in bytes. We have already explainedthe methods used to represent bytes

1. a : drive and b: drive: The A and B drives on a desktop computers were originallyreserved in the BIOS for floppy disks as at that time floppy drives were very popular and atone time there used to be floppy drives of different sizes. Floppy disk or diskette used to
http://www.webopedia.com/TERM/P/PROM.htmlhttp://www.webopedia.com/TERM/P/PROM.htmlhttp://www.webopedia.com/TERM/P/PROM.htmlhttp://www.webopedia.com/TERM/P/PROM.htmlhttp://www.webopedia.com/TERM/E/EPROM.htmlhttp://www.webopedia.com/TERM/E/EPROM.htmlhttp://www.webopedia.com/TERM/E/EEPROM.htmlhttp://www.webopedia.com/TERM/E/EEPROM.htmlhttp://www.webopedia.com/TERM/E/EEPROM.htmlhttp://www.webopedia.com/TERM/E/EPROM.htmlhttp://www.webopedia.com/TERM/P/PROM.html


32/61

comes in two basic sizes; 5.25 inch and 3.5 inch. Both have a low and high density versionsthough 3.5 inch high density disks are the most common. The later date diskettes that wereinserted into the a: drive were 3 inch size which could hold 1.44 megabyte ofinformation. Initially these disk had to be formatted before being put to use, but lateron pre-formatted disks were available. Formatting prepares the disk to be written upon.Diskettes can also be write-protected. This prevents you from writing on the disk. To write-protect a disk, slide the corner tab to uncover the opening. However, now a days most ofthe PCs do not have either A or B drives as floppy has become obsolete.

2. c: drive is popularly reserved for the hard disk drive in computers It is a thick Frisbee-like disk inside the computer, which can hold considerable highe r information than adiskette. The hard disk drive reads and stores information faster than the a: drive. Thememory size of these hard disks has greatly enhanced in last few years.

3. d : drive is mostly used for CD-ROM i.e. for playing the CDs . CDs are inserted into thisdrive. A CD can contain more information than 100 diskettes. Computers are not able towrite to the CD-ROM drive unless a CD Burner is present. The CD-ROM drives readinformation at various speeds. However, sometimes d: drive is a part of the Hard Disk assuch disks are partitioned into more than one segment where c:, d: and even e: are usedfor hard disk which has been partitioned.

In addition to above standard features for drives, now a days :

4. Some computers today come equipped with a zip drive. A zip drive provides additionalstorage space. A zip disk is inserted into the zip drive. The zip disk can hold 100 megabytesof information. Zip drives can be attached to an existing computer.

5. DVD (Digital Versatile Disc) drive is a new technology that stores more information thana CD-ROM and can be written upon. A DVD disk is inserted into this drive. The drive maycome built into the computer or may be attached. These disk often are used to store moviesor interactive video games. The disk resembles a CD but has 7 times the storage capacity.

6. Pen Drives are now popular and may be shown as e: or f: drives. These are used tostore data which needs to be carried somewhere else.

Disk size Amount of storage Approximate printed8.5 x 11 inch pages


33/61

3.5 high density 1.44 Mb 720 pages

CD 650 Mb a small library

DVD 4.5 Gb a feature length movie

DVD dual layer 8 Gb a long feature length movie with extras

Methods Used for Reading of Memory :

Sequential access refers to reading or writing data records in sequential order, that is, onerecord after the other. To read record 10, for example, you would first need to read records1 through 9.

This differs from random access , in which you can read and write records in anyorder. Some programming languages and operating systems distinguish betweensequential-access data files and random-access data files, allowing you to choose betweenthe two types. Sequential-access files are faster if you always access records in the sameorder. Random-access files are faster if you need to read or write records in a randomorder.

Devices can also be classified as sequential access or random access. For example, a tapedrive is a sequential-access device because to get to point q on the tape, the driveneeds to pass through points a through p. The disk drive, on the other hand, is arandom-access device because the drive can access any point on the disk withoutpassing through all intervening points.

Computer SoftwareSoftware Overview

Software are computer programmes that allow the user to complete atask. Broadly speaking the software can be an operating system or anapplication which is work specific and works within the environment of theoperating system. However, sometimes words software and application areinterchangeably used. Software needs to be accessed before it can be used.There are many terms used for process of accessing software including running,executing, starting up, opening, and others.


34/61

We can classify the software to be Operating Systems, Word processors,Spreadsheets, Database, Internet Browsers, Emails, Graphic programmes. .

All software are stored in files. These files are stored on a disk, card, tape orsome storage devices available. There are millions of different pieces of

software available for almost every conceivable need. Such Software areavailable commercially through stores and mail order and also available on theInternet. Software are also sometimes available through an

Open Source license which allows anyone to use the same free of charge as longas the license is maintained. If you cant find the application that you need,software development companies can design software as per your specific needs.

An operating system consists of a set of programs, which control, coordinates andsupervises the activities of the various components of a computer system. Its function is tolink between the computer hardware and user. Without an operating system, a computer isuseless. Thus, we can say that o perating system software have direct control andaccess to the computer hardware and memory locations . They perform I/Ooperations on various memory locations , and control the hardware , to make theapplication software do a task .

Some examples of Operating systems/ system software are :

1) Microsoft Windows

2) Linux

3) Unix

4) Mac OSX

5) DOS

6) BIOS Software


35/61

7) HD Sector Boot Software

8) Device Driver Software i.e Graphics Driver etc

9) Linker Software

10) Assembler and Compiler Software

MSDOS : It is among the older operating system software and now a daysrarely used as Windows have replaced this once very popular software. The termDOS stands for Disk Operating System developed by Microsoft for micro computer. It isthe only OS, which can be loaded in the main memory of the computer using a single disk.

It is a single user operating system.

It has a character user interface.

MS DOS provides all the commands for file handling.

Characteristics of DOS

It is not case sensitive.

The file names are restricted to 8 characters only.

It does not support space entries in the file name.

Broad Categories of Operating System

a) Graphic User Interface (GUI) : Itcontains graphics and icons that can be regulated bymouse. Some of the GUI operating systems are as follows:

System 7.X ; Windows 98 ; Windows CE

b) Multi-user : With the help of multi-user operating system, a computer can be used bymore than one user at the same time or in different time intervals. Some of the examples ofmulti-user operating system are as follows:

Linux ; Unix ; Windows 2000


36/61


37/61

Email clients (Outlook, Eudora, Entourage) Used for sending emails and files toother people

Desktop Publishing (PageMaker, InDesign, QuarkXPress) used for making amagazine a poster or an advertisement;

Computer-aided Design software (AutoCAD, SolidWorks, MicroStation) used tocreate blueprints or designs;

We have already clarified that all computers need some sort of Operating System(OS) so as to access and control the hardware. Now a days, on most of the PCswe use some form of Microsofts operating system s. The original Microsoftoperating system was called DOS (Disk Operating System), but the same has nowbecome obsolete. Now most computers use Windows. Windows comes in variousversions beginning with version 3.x then 95, 98, ME, XP, Vista and currently

version 7 and Version 8.1. In some computers, people use IBMs O/S2. ApplesMac use their own operating system beginning with OS 1 though to OS 10.x.

Some computer professionals, Internet Service Providers (ISP) and mainframecomputer users use an operating system such as UNIX (or a variant such asLinux), Windows NT or 2000 (Win2k) or one of the other network or server basedoperating systems.

Computer Microsoft WORDicroSoft Word

Microsoft Word is a word processor designed by Microsoft. It was first released in1983 under the name Multi-Tool Word for Xenix.

A word processor can be used to manipulate text data to produce a letter, a report,a memo, an e-mail message, or any other type of correspondence. Text data is anyletter, number, or symbol that you can type on a keyboard. The grouping of thetext data to form words, sentences, paragraphs, and pages of text results in thecreation of a document. Thus, we can say that a word processor is a program

used to type documents. Such Documents can be saved, closed and the openedagain to continue working on them.

It was not initially popular, since its user interface was different from the leading wordprocessor at the time, WordStar. The second release of Word for Macintosh, shipped in1987, was named Word 3.0 In 1993 Word for Windows 6.0 version wasreleased. Thereafter, we had Word 95, Word 97, Word 98, Word 2000, Word 2002, Office


38/61

Word 2003, Office Word 2007, were released. In 2010, was released Word 2010 and nowin 2013, Word 2013 which is also part of Office 2013 has been released.

The purpose of this tutorial is not to teach as to how to operate Word software,but to give you idea to some of the commands and procedures followed in day today use of the application. The material given here has been compiled keepingin view the questions asked in the competition exams.

What is MS Word used for?

MS Word is used for creating documents such as letters, brochures, learning activities,

tests, quizzes and students homework assignments. There are many powerful featuresavailable in Microsoft Word to make it easier to learn for students with disabilities.

.

The components of a word window are asfollows:

a)Title Bar : It shows the name of the file on which you are working. It also consists ofthree buttons as Minimize button reducing the window to an icon, Restore button bringingword window to the maximum original size and close button bringing us out of word.

b) Menu Bar: It consists of various commands.

c) Standard Tool Bar : It displays the symbols for the common operation like open, print,save, etc.

d) Formatting Tool Bar: It displays the options which can be used to format our documentlike font type. Size of the font, bold, underlines, bullets, alignment, etc.

e) Ruler : It shows the width of the document which can be increased or decreased.

f) Workspace : It is the area, where the text can be entered.

g) Vertical Scroll Bar : It is used to see the text at various positions.


39/61

h) Horizontal Scroll Bar : It is used to move from left side to right side in the documentand vice-versa .

i) Drawing Tool Bar : This is used for making drawings in the document.

j) Status Bar : This Bar will always show you your current position as for the text goes.

What is a Cursor : In computers, a cursor is an indicator used to show theposition on a computer monitor or other display device that will respond to input from a textinput or pointing device. The flashing text cursor may be referred to as a caret in somecases such as in caret browsing. The mouse cursor may be referred to as a pointer, owingto its arrow shape on some systems.

What is an insertion Point : An insertion point is the location on the screen wherethe next character typed will be inserted. This location may be in a text document, a formfield, a Web browser address bar, or anywhere else on the screen that allows textinput. The insertion point is often identified by a flashing cursor. This cursor is called an I -beam pointer and is shaped like a capital I or a long vertical line. When you type acharacter on the keyboard, it will appear on the screen directly to the right of the flashingcursor. The insertion point continues to move to the right as each character is entered.

In word, we can insert the text anywhere by clicking the mouse at the relevantpoint. On clicking the mouse button, blinking insertion point of I shape willappear on the screen the insertion point. Now if any text is typed, it will appear

just to the left of the insertion point / cursor. The text appears at the cursor.

o

Use space bar to create space between two characters;

o Use backspace to erase to the left of the cursor; and

o Use delete to erase to the right of the cursor.

o Use Enter (or Return) to move the cursor down a line.

Word processors allows you to type your text in Bold, Italics or Underline. Toactivate Bold, Italics or Underline click the icon button on the Toolbar, type the


40/61

text that you wish to have highlighted then press Toolbar icon again when you arefinished. The indicator on the Toolbar will appear highlighted as long as thehighlight style is on.

There are large number of short-cuts available for various commands in MS

Word. We give below some of the major short cuts that are available:

Common tasks in Microsoft Word

To do this Press

Make letters bold. CTRL+B

Make letters italic. CTRL+I

Make letters underline. CTRL+U

Decrease font size one value. CTRL+SHIFT+<

Increase font size one value. CTRL+SHIFT+>

Decrease font size 1 point. CTRL+[

Increase font size 1 point. CTRL+]

Remove paragraph or character formatting. CTRL+SPACEBAR

Copy the selected text or object. CTRL+C

Cut the selected text or object. CTRL+X

Paste text or an object. CTRL+V

Paste special. CTRL+ALT+V

Paste formatting only CTRL+SHIFT+V


41/61


42/61

Switch between the last four locations that youhave edited.

ALT+CTRL+Z

Open a list of browse options. Press the arrowkeys to select an option, and then press ENTERto browse through a document by using theselected option.

ALT+CTRL+HOME

Move to the previous browse object (set inbrowse options).

CTRL+PAGE UP

Move to the next browse object (set in browseoptions).

CTRL+PAGE DOWN

Edit and move text and graphicsDelete text and graphics

To do this Press

Delete one character to the left. BACKSPACE

Delete one word to the left. CTRL+BACKSPACE

Delete one character to the right. DELETE

Delete one word to the right. CTRL+DELETE

Cut selected text to the Office Clipboard. CTRL+X

Undo the last action. CTRL+Z

Cut to the Spike. CTRL+F3

Computer Microsoft Excel Overview

Microsoft Excel

MS Excel stands for MicroSofts spreadsheet programme that is used for storing, organizingand manipulating data. This software is a powerful computer programme is a part of the


43/61

MS Office and is available for operating system of Microsoft Windows and Mac OS X. This isthe most used spreadsheet programme these days. We give below a screen shot of ExcelScreen with some inputs about how it can be useful for calculation of salary of employees inan organisation. It has the ability to perform complex operations, save time and improveefficiency.

Microsoft Excel is a spreadsheet application.

It is a part of MS Office.

It features calculation, graphic tools, pivottables and a macro-programming language calledVisual Basic For Applications (VBA).

.

A look at the above Excel screen shows that spreadsheet is a rectangular table with gridsof rows and columns. The horiz ontal rows are identified by numbers (1,2,3,4,5.) and thevertical columns with letters of alphabet (A,B,C,D,E.).

MS Excel popularly known as Excel is a very powerful software with so many features thatit is not possible to discuss even a fraction of these in these pages. The features includecalculation, graphing tools, pivot tables and a macro programming language called Visual

Basic for Applications.

What is a Cell in Excel ?

The intersection point (i.e. the small rectangular box) between a column and a row is calleda Cell. This cell is the basic unit for storing data in the spreadsheet. There can bethousands of cells in a spreadsheet depending on the amount of data you are storing. To
http://www.bestguru.com/wp-content/uploads/2013/10/Excel-1.jpg


44/61

identify or refer to data stored in a particular cell, i t is identified by so called cellreference. For example, in the above screen shot, 5000 is in cell referred as B4. Thus,we can say that cell reference is a combination of the column letter and the row number.

Can You Give Me Some of the Uses of MSExcel :

Excel is used for a large number of functions. Some of the functions for which Excel iswidely used includes, (a) Managing data records like name list (you are easily sortalphabetically); (b) Analysis through pivot tables; (c) corporate budgeting; (d) creatingforms and consolidating results; (e) inventory management ; (f) Breakeven analysis.

Some important terms relating to MS Excel :

a) Worksheet : It is a grid of cells made up of horizontal rows and vertical columns. Itcontains 65536 rows and 256 columns.

b) Row Number : Each row is given a number 1,2,3,4, . So on.

c) Column Letter : Each column is given a letter starting from AZ, AA.ZZ,BABZ, .IA IV.

d) Cell : It is basic unit of worksheet where numbers, text, formulae, etc, can be place.

e) Cell Pointer : It is a cell boundary that specifies which cell is active at that moment.

f) Current Cell : It is a cell which is active.

g) Range of Cell : It is a group of contiguous cells that forms a rectangular are in shape.

h) Work Book : A worksheet is a grid of cells made up of rows and columns. Multiple

worksheets can be combined under a file known as Work Book.

i) Data in Worksheet : Three types of data can be entered, numbers/characters,text and formulae.

j) Formula : It is a sequence of values, cell address, names functions or operators in a cellthat produces a new value from existing values.


45/61

k) Cell Referencing : Each cell in worksheet has a unique address, when cell address isreferred in formulas, it is called Cell Referencing.

l) Relative Referencing : Cell referencing in which the cells are referred by their relativeposition in the worksheet relative to a particular cell.

m)Absolute Referencing : Cell referencing in which the cells are referred by their fixedposition in the worksheet.

n)Mixed Referencing : Combination of relative and absolute referencing is called MixedReferencing

o)Functions : Functions are predefined formulae that perform calculations by using specificvalues called arguments.

p) Structure : The structure of a function begins with the function name, followed by anopening parenthesis, the arguments for the function separated by commas and a closingparenthesis.

q) Charts : Charts are the pictorial representation of worksheet data.

r) Area Chart : An area chart emphasizes the magnitude of change over time.

s) Column Chart : A column chart shows data changes over a period of time.

t) Bar Chart : It illustrates comparisons among individual items.

u) Line Chart : It shows trends in data at equal intervals.

Excel Keyboard Shortcuts

The following keyboard short cuts can be used to increase the speed and smoothfunctioning in the MS Excel spreadsheet work.:

Hide / Unhide shortcuts:

CTRL+9 Hide the selected row(s)

CTRL+SHIFT+( Unhide any hidden row(s) within selection


46/61

CTRL+0 Hide the selected column(s)

CTRL+SHIFT+) Unhide any hidden column(s) within selection

Navigation shortcuts:

HOME Move to the beginning of the Row

CTRL+HOME Move to the beginning of the Worksheet

CTRL+END Move to the bottom-most and right-most used cell in theWorksheet

CTRL+PAGDOWN Move to the Next Sheet in the workbook

CTRL+PAGEUP Move to the Pervious Sheet in the workbook

ALT+PAGEDOWN Move one screen to the Right

ALT+PAGEUP Move one screen to the Left

Selection shortcuts:

CTRL+SHIFT+PAGEDOWN Select the current sheet and next sheet

CTRL+SHIFT+PAGEUP Select the current sheet and previous sheet

CTRL+SPACE Select the entire COLUMN

SHIFT+SPACE Select the entire ROW

CTRL+* Select current range

CTRL+SHIFT+O(letter O) Select cells that contain Comments

CTRL+SHIFT+* Select the current region around the active cell

CTRL+ / Select the array containing the active cell


47/61

CTRL+] Select all cells that contain formulae that directly referenceactive cell

CTRL+SHIFT+} Select all cells that contain formulae that directly orindirectly reference active cell

Date & Time related shortcuts:

CTRL+; Insert current date

CTRL+SHIFT+: (COLON) Insert current time

Number Formatting shortcuts:

CTRL+SHIFT+~ General Format the numbers in selected range

CTRL+SHIFT+% Apply Percentage format to numbers in selected range

CTRL+SHIFT+$ Apply Currency format to numbers in selected range

CTRL+SHIFT+# Apply date format (dd/mm/yy) to the selected cell(s)

CTRL+SHIFT+^ Apply Exponential number format with 2 decimal places tothe selection

CTRL+SHIFT+! Apply Number format with 2 decimal places, thousandsseparator and minus sign for -ve numbers

General Cell / Range Formatting shortcuts:

CTRL+1 Format cells menu

CTRL+SHIFT+& Apply outline border to the selection

CTRL+SHIFT+ _ (underscore) Remove the outline border to the selection


48/61

CTRL+5 Apply (or remove) Strikethrough format to the selection

CTRL+B OR CTRL+2 Apply (or remove) Bold format

CTRL+B OR CTRL+3 Apply (or remove) Italic format

CTRL+B OR CTRL+4 Apply (or remove) Underline format

Copy data shortcuts:

CTRL+D Fill Down

CTRL+R Fill Right

CTRL+, (comma) Copy formula from cell above to the active cell

CTRL+ (double quotes) Copy value from cell above to the active cell

Other shortcuts:

CTRL+K Insert hyperlink menu

CTRL+(~) Toggle formula view

F4 Repeat last action

F11 Chart selected data

Computer Microsoft PowerPoint

Microsoft Power Point Software

Powerpoint is the presentation graphics part of MS Office suite.

Powerpoint can create various presentation materials like charts, graphics, slides,handouts, overheads, etc.

Powerpoint even creates slide shows.


49/61

Auto Content Wizard, Design Templates, Sample Presentation and Blank Presentationare the methods for creating new presentation.

Presentation can be saved and run in any of the file formats: the 2003 default .ppt(presentation),

Pps (powerpoint show) or .pot (template).

Custom animation can be used to create small story boards by animating pictures toenter, exit or move.

Powerpoint presentation can be made up of a number of pages or slides.

Computer Microsoft AccessMicrosoft Access Software

Microsoft Access is a relational database management system that combines therelational Microsoft Jet Database Engine with a graphical user interface and softwaredevelopment tools.

It stores data in its own format based on the Access Jet Databases.

It can also import or link directly to data stored in other Access databases.

A database is a collection of data of a particular type.

Data in a database is stored in the form of tables.

A table is a row and column arrangement of information.

A table is also called a Relation.

The table contains data organized under specific categories.

Each such category is arranged vertically in a table and is called a Column.

Every column in a table has a unique name.

A column can also be referred to as a field.

Data organized horizontally is termed as a row.


50/61

Relational Database Management System (RDBMS) is a multi-table database wherethe tables in the database have to be related for storing or retrieving data.

Microsoft Access is an RDBMS that enable to manage relational database in awindows environment.

MS Access enable you to enter, retrieve and modify data and also create forms andreports.

Database Objects

a) Table : They store data in a row and column format similar to spreadsheets.

b) Queries : They enable you to view data from a table.

c) Forms : They enable you to enter, view and modify in a table.

d) Reports : They enable you to generate reports based on tables and queryresults.

e) Data Access Page : They are web pages to view data from theinternet where the data is stored in an Access database.

f) Macros : They are a series of commands and functions that can be executedwhenever a task is needed to perform.

g) Modules : They are a set visual basic procedures and declarations stored asone unit.

Computer What happens when we switch onthe computer

What Happens When We Switch On Computer

When we put power on in our computer, it first of all loads the operatingsystem. This procedure popularly is known as booting up of computer. Thus, wecan say that the computer starts from scratch every time we turn the power


51/61

on. It checks all its components. In case there is any problem with anycomponent, it will usually display a message. Loading the operating system isusually automatic.

On most PCs these days, Microsoft Windows is used. However, Mac OS or Linux as theiroperating system are also used by some users. All these Operating Systems (OS) areGraphic User Interface (GUI) systems and thus allows the user to control or run thecomputer using a Mouse and clicking on the icons. The user simply moves the mouse on aflat surface, rolls the trackball, or moves their hand over the touch pad to control a pointer.They then choose the option they want by pressing a button or touching the pad.

Without a GUI the user controls the computer using the keys on the keyboard. This isreferred to as a Command Line Interface (CLI) which was popular under DOS environment.

Once the system is loaded the user can start the application or program that they are goingto use.

A typical computer process includes

(a) inputting the information;

(b) Processing the information;

(c) Outputting the information.

The information is inputted through input devices like keyboards, mouse, disks, scanners

and other devices. The information is processed in CPU and the processed informationdisplayed either on Monitor (soft copy), stored on the disk, or taken as a hard copy througha printer.

Computer Data Communication and NetworkSome Basic Facts


52/61

Signals are electric or electromagnetic encoding of data and signaling is propagationof signal along suitable communication medium.

Transmission is communication of data achieved by the propagation and processing ofsignals.

In parallel data transmission, each wire carries a bit of information.

In series data transmission, each bet is sent sequentially one after another and it isslower than that of parallel transmission.

In synchronous transmission, characters are transmitted as groups, with controlcharacters in the beginning and at the end of the bit train.

In a synchronous transmission, each character is transmitted separately.

In simplex mode of communication, channel is used in one direction.

In half duplex mode of communication, channel is used in both directions.

In full duplex mode, the communication channel is used both directions at the sametime.

Computers are connected with each other for communication creating the

computer network. Computer network is of three types:

1. Local Area Network (LAN) 2. Metropolitan Area Network (MAN) 3. Wide Area Network (WAN)

Local Area Network (LAN) It is a data communication network, which connects manycomputers of workstations and permits exchange of data and information amongthemselves, within a localized area.

Metropolitan Area Network (MAN) It is a network of computers of a large region. Forexample, all the branched of an electric department of a city and the network of computersof all the offices.

Wide Area Network (WAN) It is a network linking separate geographical locations.Internet is the best example of it.


53/61

Computer TopologyTopologies Used in Computer

A network topology is the physical layout of the network in which all thedevices are connected among themselves. The point of connection to the networkby the stations are called Computer Nodes or Link Stations .

When a number of stations are connected directly to the central station orcontroller it is known as Star Topology .

When all the stations are connected to a single communication line that isreferred to as a bus, it is known as Bus Topology .

When all the stations are connected with each other in a logically circular form, it isknown as Ring Topology. Failure of a station in a ring topology causes the disruption in theentire ring framework.

Computer Uniform Resource LocatorURL

Each Internet service employs a particular protocol. This specific protocol definesthe rules of engagement for computers conveying the information on that

particular service. This protocol is shown at the beginning of the UniformResource Locator (URL) for each site. For example, the URL for a website isfrequently in the form of http://www.bloggs.com , indicating that this is an HTTPconnection.

URLs are sometimes known as a Uniform Resource Identifier (URI) , or popularly inshort as an address ..

URLs can contain both uppercase and lowercase letters, although it doesnt usually matter which case is used for any of the letters. In all instances, however, they can only containstandard ASCII characters, corresponding to those that you can actually see on yourcomputer keyboard. Note that spaces or other control codes are not permitted.

Suffixes and Top-Level Domains :

Most of the time we use .com at the end (i.e. suffix) of the domainname. However, some of other common URL suffixes, are:-


54/61


55/61

.eu European Union

.fr France

.in India

.jp Japan

.kr Korea

.su Ex-Soviet Union state

.uk United Kingdom

.us USA (Other sites)

Computer Important Terms Used in InternetInternet Overview and Terms Used

An Internet is a global connection of computers linked together by cables and telephonesand makes the communication possible among them. We can also say that an internet isa computer network consisting of a worldwide network of computer networks that use theTCP/IP network protocols to facilitate data transmission and exchange. The following aresome of the basic rules used for transferring the data across internet.

For such communication, the address of the destination and a safe means of movingdata are required.

The rules governing the sending and receiving of data on the Internet areimplemented in two parts as Transmission Control Protocol (TCP) and InternetProtocol (IP).

Transmission Control Protocol divides the data into little data packets.

The rule of Internet Protocol here is put destination addressing information on suchpackets.

Hosts are in general, individual machines at a particular location.

Domains are general category that a computer on the internet belongs to.


56/61


57/61

Uniform Resource Locator (FTP) is a way to avail of Internet resources.

File Transfer Protocol (FTP) is used to access a remote Internet host.

Modem is a device allowing a computer to transmit information over a telephone

line. It acts as a modulator and demodulator while the process of transmitting andreceiving.

Wide Area Information Service (WAIS) i s a type of service to access textdatabases or libraries on the Internet.

Mosaic gives access to Internet resources by using graphical user interface allowingusers to navigate through hypertext documents.

Archie is used to locate files available by anonymous FTP, it is also known as Global

Librarian.

Home Computer Awareness Computer CAPTCHA

Computer CAPTCHA

What is CAPTCHA ?

A CAPTCHA is a program that can generate and grade tests that humans can passbut current computer programs cannot. For example, humans can read distorted

text (as the one given below), but current computer programs cant

What is full form of CAPTCHA :

The full form of CAPTCHA is Completely Automated Public Turing test to tellComputers and Humans Apart. This is a trademark of Carnegie MellonUniversity, and can be termed as a type of challenge-response test used incomputing to determine whether or not the user is human. The term was coined in2000 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper of Carnegie MellonUniversity, and John Langford of IBM.
http://www.bestguru.com/http://www.bestguru.com/http://www.bestguru.com/computer-awareness/http://www.bestguru.com/computer-awareness/http://www.bestguru.com/computer-awareness/http://www.bestguru.com/computer-awareness/http://www.bestguru.com/


58/61

The most common type of CAPTCHA was first invented by Mark D. Lillibridge,Martin Abadi, Krishna Bharat, and Andrei Z. Broder. This form of CAPTCHA requiresthat the user type the letters of a distorted image, sometimes with the addition ofan obscured sequence of letters or digits that appears on the screen. Because thetest is administered by a computer, in contrast to the standard Turing test that isadministered by a human, a CAPTCHA is sometimes described as a reverse Turingtest. This term is ambiguous because it could also mean a Turing test in which theparticipants are both attempting to prove they are the computer.

What are the uses of CAPTCHA ?

CAPTCHAs have several applications for practical security. Some of the importantuses of CAPTCHA are as follows:-

It Prevents Comment Spam in Blogs We have heard that in some casesbogus comments are submitted either as a spam or to to raise search engine ranksof some website. Usually, such spam comments are generated through computerprogrammes. Thus, by using a CAPTCHA websites can eliminate such spamcomments as in that case only humans can enter comments on a blog.

To Prevent Fake Registration There are many companies which offerfree email services. Till few years back, most of such services experienced botsattack that would sign up for thousands of email accounts every minute. The

problem was resolved by introduction of CAPTCHA before final submission of thedetails as it ensured that only humans obtain free accounts. In general, freeservices should be protected with a CAPTCHA in order to prevent abuse byautomated programs.

Online Polls - In order to prevent fake polling votes , CAPTCHA plays animportant role.

Preventing Dictionary Attacks . CAPTCHAs can also be used to preventdictionary attacks in password systems. The idea is simple: prevent a computer

from being able to iterate through the entire space of passwords by requiring it tosolve a CAPTCHA after a certain number of unsuccessful logins.

Worms and Spam . CAPTCHAs also offer a plausible solution against emailworms and spam: I will only accept an email if I know there is a human behindthe other computer. A few companies are already marketing this idea


59/61

Computer WHAT ARE VIRUS, WORM,TROJAN HORSE

VIRUS, WORM AND TROJAN

A virus is a program or code that replicates itself onto other files with which it comes in contact; that

is, a virus can infect another program, boot sector, partition sector, or a document that supports

macros, by inserting itself or attaching i tself to that medium. Most viruses only replicate, though many

can do damage to a computer system or a users data as well.

A worm is a program that makes and facilitates the distribution of copies of itself; for example, from

one disk drive to another, or by copying itself using email or another transport mechanism. The worm

may do damage and compromise the security of the computer. It may arrive via exploitation of a

system vulnerability or by clicking on an infected e-mail.

A Trojan Horse portrays itself as something other than what it is at the point of execution. While it

may advertise its activity after launching, this information is not apparent to the user beforehand. A

Trojan Horse neither replicates nor copies itself, but causes damage or compromises the security of

the computer. A Trojan Horse must be sent by someone or carried by another program and may

arrive in the form of a joke program or software of some sort. The malicious functionality of a Trojan

Horse may be anything undesirable for a computer user, including data destruction or compromising a

system by providing a means for another computer to gain access, thus bypassing normal access

controls.

Computer Virus

A computer virus is a computer program that can copy itself and infect a computer. A virus can spread

from one computer to another when its host is taken to the target computer, for instance because a

user sent it over a network of the Internet, or carried it on a removable medium such as a floppy disk,

CD, DVD or USB drive. Viruses can increase their chances of spreading to other computers by infecting

files on a network file system or a file system that is accessed by another computer.

Important Facts Related to Computer Virus

The Creeper virus was first detected on ARPANET, the forerunner of the Internet, in the early

1970s.

The Reaper Program was created to delete creeper.

The actua l term virus was first used in David Gerrolds 1972 novel, when HARLIE was one.


60/61

A program called Elk Cloner was the first computer virus to appear in the wild this is, outside

the single computer or lab where it was created

It attached itself to the APPLE DOS 3.3 operating system and spread via floppy disk.

The first PC virus in the wild a boot sector virus Brains created in 1986.

With the spread of personal computer, traditional computer viruses emerged in 1980. Bulletin

board-driven software sharing contributed directly to the spread of Trojan horse programs. Shareware

and boot leg software were equally common vectors for viruses on BBS.

Macro Viruses have become common since the3 mind 1990.ost of these viruses are written in

the scripting languages for Microsoft Programs such as word and Excel and spread throughout

Microsoft Office by infecting documents and spreadsheets.

Viruses that spread using cross site scripting were first reported in 2002 and were academicallydemonstrated in 2005. There have been multiple instances of the cross site scripting viruses in the

wild, exploiting websites such as My space and Yahoo.

The most popular five computer virus came into light as far as follows :

1. I Love You (2000) It spreads through e-mails. 2. Code Red (2001) It affects window server. 3. Nimada (2001) It is the most rampant virus. 4. Melissa (1999) It spreads through World Macro and e-mails. 5. Sasser (2004) It spread by attaching to port 445 on the network windows system.

Antivirus Software and Other Preventive Measures

Antivirus software can destroy the viruses by finding them. The antivirus software uses two common

methods in order to detect viruses.

1. Using the Virus Signature Definitions list. 2. By using Heuristics Algorithm

Some antivirus programs are capable of On the Fly scanning of received e -mails along with scanning

of the open files. This process is known as On -Acc ess scanning.

Antivirus software does not alter the efficiency of the host software for the communication of viruses.

These software need to be updated regularly so that the new viruses can be detected.


61/61

The loss incurred by the viruses can also be negated by the regular backup of data on other mediums.

If any data get misplaced due to this virus then we can retrack it by backup.

Five new Computer Antivirus Software are as follows:

1) Kaspersky Antivirus 2010

2) Symantec Norton Antivirus 2010

3) McAfee Antivirus Plus 2010

4) Panda Security Antivirus Pro 2010

5) Trend Micro Antivirus + Anit Spyware 2010