pc maintenance and securitypeople.du.ac.in/~ighani/presentation/computer_basics.pdf · the computer...

University of Delhi

© Imran Ghani,2006,[email protected]

Computer Basics

byIMRAN GHANI

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What is a Computer?

The word ‘Computer’ literally means to ‘Compute’ or to ‘Calculate’. Computer is an electronic device that stores, retrieves, and processes information based on the instructions provided, to generate the desired output. Computers are available in many sizes and configurations for various types of uses such as Desktop, Laptop, Servers, PDA, etc.

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Characteristics of Computers

Speed

Accuracy

Versatility

Storage Capacity

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Evolution of Computer

Abacus: (2000 years back), a wooden rack holding two horizontal wires with beads strung on them. Fast and simple calculations can be carried out by appropriately placing the beads.

Blaise Pascal: a French mathematician, credited for building the first digital computer in 1642. He invented the mechanical calculating machine. Numbers were entered in this machine by dialing a series of numbered wheels. Another series of toothed wheels transferred the movements to a dial, which showed the results.

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Evolution of Computer (cont….)

In 1671, Gottfried Wilhelm von Leibniz , a German mathematician, invented a calculating machine which was able to add and perform multiplications. He invented a special stepped gear mechanism for introducing the addend digits.

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In 1822, Prof. Charles Babbage of Cambridge University designed an automatic calculating machine that he called the ‘Difference Engine’. It was intended to be steam powered and fully automatic (including printing of result tables), commandedby a fixed instruction program. It was a prototype of a computer which was 100 years ahead of time. Prof. Babbage is considered as the father of modern day computers.

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In 1890 Herman Hollerith and James Powers developed devices that could read information that had been punched into cards, without any human help. This resulted in reduced reading errors, increased workflow and availability of unlimited memory (punched cards could be used as easily accessible memory of unlimited size).

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First Generation Computers (1940 to 1956)

First generation computers relied on machine language (binary-coded program) to perform operations and could solve only one problem at a time. Punched cards and paper tapes were used to input data and instructions, and output was displayed on printouts. Vacuum tubes were used in the circuitry and magnetic drums for memory. Vacuum tube

Early computers like ENIAC, EDVAC and IBM 650 can all be classified as first generation computers.

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ENIAC

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Transistors (invented in 1950) and magnetic core memory were used in second generation computers. Second generation of computers was also characterized by allowing programmers to specify instructions in symbolic (or assembly) language rather than cryptic binary machine language.

Second Generation Computers (1956 to 1963)

High level programming languages like COmmon Business Oriented Language (COBOL) and FORmula TRANslation(FORTRAN) were also being developed at this time.

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Third Generation Computers (1964 to 1971)

Integrated Circuits (ICs), developed by Jack Kilby, in 1958, were used in circuitry instead of transistors. Punched cards and printouts replaced with devices like keyboards and monitors making it easier for the user to interact with the computer.

Intel 8742, 8-bit Microprocessor

Operating System such as IBM System/360 used to allowed the device to run various applications at one time.

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Fourth Generation Computers (1971 to present)

In 1970 invent of Large Scale Integration(LSI) technology and latter Very Large Scale Integration (VLSI) squeezed hundreds of thousands of components onto a single chip. This shrinking trend continued and led to the introduction of personal computers (PCs).

Intel 80486 DX2

The IC technology was not only used to construct the processor, but also for the construction of memory. The first memory chip (Intel 4004) was constructed in 1970. It was ‘four-bit’Microprocessor and could hold 256 bits.

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Computer Hardware and Software

Software

The software is the instructions that makes the computer work. Software is held either on your computer’s hard disk, CD-ROM, or on a floppy disk and is loaded from the disk into the computer’s memory, as and when required

Hardware

The term hardware refers to the physical components of your computer such as the system unit, mouse, keyboard, monitor etc. Computer hardware cannot perform any manipulation or calculation without being instructed as to what to do and how to do it.

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Schematic Representation of a Computer

Secondary Storage

Input Unit Output Unit

Central Processing Unit (CPU)

Arithmetic Logic Unit

Main Memory

Control Unit

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Input Unit

The input device serves the purpose of receiving data and instructions in a form that can be understood by the computer.

Ex: Keyboards, Mouse, digital pen, etc.

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Central Processing Unit (CPU)

Data and instructions (programs) are stored in the computer’s memory after which all the major calculations and computations are carried out within the CPU. The CPU is also responsible for controlling the operations of various units of the computer system.

Arithmetic Logic Unit (ALU): All calculations and comparisons, based on the instructions provided, are carried out within the ALU. It performs arithmetic functions like addition, subtraction, multiplication, division and also logicaloperations like greater than, less than and equal to.

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Central Processing Unit (CPU) (cont…)

Main Memory: The main memory holds data and instructions after input, till they are needed. It also holds the processed results that are awaiting output.

Control Unit: The function of the control unit is to execute the instructions of a program, one by one, in the desired sequence. It interprets each instruction and then prompts its execution by one of the units like input, output, ALU, storage.

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Central Processing Unit (CPU) (cont…)

CPU or Microprocessor

RAM

The system board or mother board containing CPU, memory, and various other ICs, etc.

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Output Unit

The processed data, stored in the memory of the computer is sent to the output unit, which then converts it into a form that can be understood by the user.

Output Devices: Display monitor, printer, etc.

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Secondary Storage

Also termed as ‘auxiliary’ or ‘backup’storage, it is typically used as a supplement to main storage. It is much cheaper than the main storage and stores large amount of data and instructions permanently.

Secondary Storage Devices: Magnetic tapes, Hard Disks, Floppy Diskettes, CD, DVD, Memory sticks, etc.

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Other Computer Peripherals

PrinterScanner UPS

Pen Drive

Modem Joystick Plotter

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BITS and BYTESA BIT (an abbreviation for BInary DigiTS), is smallest unit of data in a computer and can either store a 0 or 1

BYTES are typically a sequence of eight bits put together to create a single computer alphabetical or numerical character. Bytes are used to quantify the amount of data digitally stored (on disks, tapes) or transmitted (over the internet), and are also used to measure the memory and document size.

Kilobyte: A kilobyte (KB) consists of 1024 bytes. Megabyte: A megabyte (MB) consists of 1024 kilobytes or 1,048,576 bytes. Gigabyte: A gigabyte (GB) consists of 1024 megabytes or 1,073,741,824 bytes.

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Types of Computer Software

Operating System (OS):

OS consists of programs that control the operations of the computer system itself. It consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing. OS also provides an interface between the application programs and the computer.

Ex: DOS, MS Windows, UNIX, Linux, Macintosh etc.

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Types of Computer Software (cont…)

Application Software:

Application software are written to perform a specific task for the user, such as word processing, accounting, budgeting or payroll. Application programs run on top of an operating system and are used to carry out specific functions.

Ex: MS Word (used for word processing), MS Excel (used as spreadsheets), Oracle (used for database management), etc.

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Microsoft (MS) Windows

MS Windows is a Graphical User Interface (GUI) based

operating system having commands and options represented

on the screen in the form of small images, commonly known

as icons. MS Windows performs three major functions:

• It controls and coordinates the various resources of the computer like memory, storage and input/output devices.

• It manages all the files and folders and allows a user to perform various file and disk management tasks.

• It also acts as an interpreter between other software and hardware.

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Various Versions of Windows

Windows 1.0 1985

Windows 2.0 1987

Windows 3.0 1990

Windows 3.1 1992

Windows NT 3.1 1993

Windows 95 1995

Windows NT 4.0 1996

Windows 98 1998

Windows 2000 2000

Windows ME 2000

Windows XP 2001

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Functions of Mouse buttons

Left button

Right buttonScroll while

Left Click : Used to select an item.

Double Click : Used to start a program or open a file.

Right Click : Usually used to display a set of commands.

Scroll while: Used to scroll the pages.

Mouse Actions

Drag and Drop : It allows you to select and move an item from one location to another. To achieve this place the cursor over an item on the screen, click the left mouse button and while holding the button down move the cursor to where you want to place the item, and then release it.

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Layout of a keyboard

Cursor Moment Keys

Numeric keypad

Space BarAlphanumeric keypad/ Special function keys

Function keys

Other Important keys: Enter, Backspace, Delete, Insert, Shift, Caps Lock, Tab, Ctrl, Alt, Esc

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Desktop

Icons

Start button Quick lunch bar Clock

Desktop Background

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Control Panel

Control Panel is like a dashboard of your computer. It contains various tools which are used to load/ unload software, creating users and groups, change configuration and settings such as; Date and Time, Desktop background, Screen Saver, Localization, Display, etc.

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Windows Explorer

You may use Windows Explorer and to explore and mange Files and Folder stored in your computer. Minimize

MaximizeClose

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Computer Networking

Connecting two or more computers together to exchange information is known as computer networking.

A network can be as simple as linking two computers or may consist of hundreds and thousands of different types of computers and peripherals, connected directly or indirectly.

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Use of Computer Network

1. Easy and real time data transferring.

2. Data or information sharing.

3. Resource sharing.

4. Centralized computer administration and

maintenance.

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Mode of Networking

Local Area Network (LAN): small computer network such as; computers connected in a college lab or in office. UTP cabling or WiFi are used to connect the computers.

Metropolitan Area Network (MAN) or Campus Network: a computer network spread all over a city or a campus. Computers being connected through OFC, UTP, WiMaxand WiFi.

Wide Area Network (WAN): a very large computer network spread across a big city or over many cities. Various technologies such as; RF link, OFC, UTP, WiMaxetc. are used to connect computers.

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Computer Connectivity Options

UTP Cabling:

Data transfer rate: 100-150 MBPS

Max. cable length: 100mt

Use: LAN

Switch

UTP Cable with RJ45 connector Star Topology

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Computer Connectivity Options (cont….)

Optical Fibre Cabling (OFC):

Data transfer rate: 100-150 MBPS Max. cable length:

MM: 500mt

SM:10-30km

Use: LAN Backbone, MAN, Campus Network

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Computer Connectivity Options (cont..)

Dial-Up Dial-up provides connecting adevice to a network using modem over the public telephone network. Maximum data transfer rate over a dial-up connection is limited to 56 kbps (56,000 bits per second).

Use: Home PC connectivity

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Integrated Services Digital Network (ISDN)

ISDN, is a digital communications line. It allows for transmission of data, voice, video and graphics, at very high speeds, over standard communication lines. ISDN is not restricted to public telephone networks, but can use packet switched networks, CATV networks, telex etc.

Use: On demand high speed Internet

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Digital Subscriber Lines (DSL)

A DSL connection is a very high-speed connection that uses the same wires as a regular telephone line. The download speed of DSL ranges from 128 kilobits per second (Kbit/s) to 24,000 Kbit/s. and the connection can be left open, while you use your phone line for voice calls!

Use: Home TV or high speed Internet

A typical DSL Modem

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Leased Line

It is like a ‘private circuit’ between the two machines. A leased line can be a twisted pair, coax cable, or a fibre optic cable. Leased lines have 1.544 Mbps data transfer rate.

Use: Connecting two branches of any office, all time Internet connectivity

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Radio or RF Link

Point to point Radio

Point to Multipoint Radio.

Frequency Band: 2,700-2,900 MHz.

Throughput: 4 Mbps.

Use: WAN

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Internet Protocols‘Protocol’ defines a set of rules or code of behavior. In the context of networking, protocol defines a ‘language’ of conventions and rules that specify how the data will be packaged, sent and acknowledged.

IP Address

The Internet Protocol (IP) address is an unique number that defines the location of your computer, such that it is an identifiable machine within all the computers connected to the Internet. This is a 32-bit number and is divided into four octets.

For example, the IP address (10.0.0.2.)

00001010 00000000 00000000 00000010

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Domain Naming System (DNS)

Domain Naming System (or Service), commonly known as the DNS, is an Internet service that translates domain names to or from IP addresses.

Abbreviation What It Representscom Commercial organizationorg Non-profit organizationsnet Networking organizationsgov Government agenciesedu Educational institutionsac Academic in Indian organization

Commonly Used Abbreviations in Domain Names

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Internet

The Internet is simply a series of computers, linked to

one another around the world, communicating almost

instantaneously with one another. It comprises tens

and thousands of computer networks communicating

with each other like a big net or web. It can be

termed as a ‘network of networks’. These computer

networks are physically linked with one another

through telephone, radio, cable lines, satellite, or even

fiber optic.

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World Wide Web (www)

World Wide web is commonly known as the ‘Web’ it consists

of Internet servers that are connected through hypertext.

These texts are created in a language called HTML

(HyperText Markup Language) which supports links to other

documents, as well as graphics, audio and video files.

Hyperlinks allow the user to navigate from one document to

another without having to worry about the actual location of

the document (which could be the same or another server

located miles away).

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Website

The web can be understood as a collection of thousands

and millions of information locations connected to each

other. Each such location is called a website. A website

comprises web pages . A website can be created by an

individual or by an organization.

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Uniform Resource Locator (URL)

An URL defines the address of a site on the Internet. It is an abbreviation of Uniform Resource Locator, and states the global address of documents and other resources on the World Wide Web.

For example :http://www.du.ac.inhttp://people.du.ac.in/~ighani

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Internet Browser or Web Browser

Internet browsers are application software used for Internet browsing or web surfing.

Examples: Internet Explorer, Motzilla, FireFox

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Search Engines

Search Engines are specific type of

websites used to search information on

Internet

For Example: http://www.Yahoo.com

http://www.google.com

Within the search engine you enter a

word or phrase and it will retrieve

documents from the Internet based on

the information you typed in.

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E-mailing

E-mailing is one of the most common and popular uses of the Internet.

You can send or receive mails from anywhere in the world almost

instantaneously. Through e-mail, you can send and receive any type of

file – image, video, sound, and plain text. It is a very versatile and open

medium with the advantage of being a low cost one.

If you wish to send and receive e-mails, you will need to create an e-mail

account for yourself, using a website that offers such services.

Examples of E-mail sites: Rediff.com, yahoo.com, hotmil.com

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Internet Chat

Internet Chat allows you to type in a message, and your friend

(anywhere in the world, but logged on to the Net at the same time

on the same chat site) would receive it almost instantaneously who

can then respond in the same way.

There are various free chat sites that you can use to communicate

with other people for example: Yahoo.com, hotmail.com.

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Downloading Information from Internet

Many websites provide information for download (moving copy of the file from website server to your PC). You may download that files from the server and store in your computer.

1. Open the website and Click the download link.

2. Click Save in File Download window.

3. Specify the folder and click Save.

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Internet Explorer SecurityInternet Explorer (IE) provides a number of features that

help to protect your privacy and make your computer and

your personally identifiable information more secure.

Privacy settings:

1.Specify how your computer deals with cookies. Cookies are files created by a Web site that store information on your computer, such as your preferences when visiting that site. Cookies may also store personally identifiable information, such as your name or e-mail address.

2.Privacy alerts that let you know when you try to gain access to a site that doesn't meet the criteria in your privacy settings.

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Internet Explorer Security (cont….)

Security features:

1. Help to prevent people from gaining access to information that you have not given them permission to access, such as credit card information you enter when shopping on the Internet.

2. Security features can also protect your computer from unsafe software.

3. Block most pop-up windows.

4. Update, disable, or re-enable Web browser add-ons.

5. Enhanced security features to warn you when a Web site is trying to download files or software to your computer.

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Internet Explorer Security (cont….)

Configuring Security features of IE:

1. Open Internet Explorer and click “Tools”.

2. Click “Internet Options”, and go to “Security” tab. Here you may define security for Internet and Local Intranet. You may also list the names of “Trusted” and “Restricted” sites.

3. You can use “Custom Level” button to set the level of security according to your need.

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Antivirus

What is a Virus?

A virus is a program that can be hidden inside another file — it replicates itself and spreads to other files and computers.

Source of Virus:

• Shared files, networks, floppy disks

• E-mail attachments

• Web-based e-mail

• Downloads

• Malicious Web sites

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What can Virus do?

1. A virus (worm) can copy itself multiple times and infect your computer by occupying hard disk space, choking your network bandwidth etc.

2. Some viruses contain code that inflicts extra damage by deleting files or lowering your security settings, inviting further attacks.

3. A virus even format hard disk of your computer.

4. A type of virus (called Trojan Horses) can scan your hard disk and send important information to the source.

5. An e-mail virus can scan your address book and send e-mails using your e-mail account.

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Antivirus (cont…)

Antivirus software is designed to detect known viruses. When a new virus hits the world, the antivirus software manufacturers normally have an update available for download on their Web sites within hours. In addition to using up-to date antivirus software, you should also make sure that it has a "real-time scanning" feature. Setting up your e-mail and Internet browsing software so that it is more difficult for files containing viruses to make their way onto your computer at all is another good step.

Your most important defense against viruses is antivirus software: Install it, use it, and keep it up to date. This software is essentialas a defense against viruses.

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Windows Update

Windows Update is the online extension of Windows that helps us to keep our computer up-to-date. We may use Windows Update to updates our computer’s operating system, software, and hardware drivers. New content is added to the Microsoft site http://windowsupdate.microsoft.comregularly, so anyone can always get the most recent updates and fixes to protect his/ her computer.

Click Windows Update

in All Programs list.

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Windows Update (cont….)

Setting your PC for automatic

Updates:

1. Double click System in Control

Panel.

2. Click Automatic Updates tab and

select other parameters

according to your preference.

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PC Maintenance

Tasks required in order to maintain and improve performance of your PC:

1. Data and System Backup

2. Detecting and Repairing Disk errors.

3. Disk cleaning.

4. Disk De-fragmentation.

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Backup.

You may create System Recovery Disk, which is required to restore the system after major crash. You can also take backup of your data, and favorites, desktop and cookies settings.

1. Click Start, then click

All Programs.

2. Click Accessories, and

then click

System Tools.

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Repairing Disk.

Detecting and Repairing Disk errors:

1. Open “My Computer”, and select the local disk you want to check.

2. On “File” menu, click Properties.3. On the “Tools” , under “Error-

checking”, click :Check Now”.4. Under “Check disk options”,

select the “Scan for and attempt recovery of bad sectors” check box.

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Cleaning Disk

Disk Cleanup:

This tool will detect your PC for

temporary files, old setup files, and for

not required application software and

remove it from your PC.

You may run “Disk Cleanup” tool in

“System Tools” of Accessories tab

available in All Programs.

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Disk-Defragmenter.

The scattering of parts of the same disk file over different areas of the disk occurs over a period of time mainly due to deletion and addition of files on disk. It slows disk access and Degrades the overall performance of disk operations. You can use Disk Defragmenter tool to analyze local volume (hard disk space), and to Locate and Consolidate fragmented files and folders.

• Click Start, then click All

Programs.

• Click Accessories, and

then click System Tools.

• Double click Disk

Defragmenter.

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PC Maintenance and Security-Tips

1. Work with your computer with user logon, not with administrator logon for day-to-day work.

2. Keep your computer updated with the latest critical updates and security patches.

3. Keep your Antivirus up-to-date and run regularly.4. Keep your Office update with the latest critical

updates.5. Keep your Firewall always ON.6. Back up data regularly.7. Download files only from trusted sites.8. Run Disk Cleanup and Disk Defragmenter tools

periodically.

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Thanks.

IMRAN GHANISR. SYSTEM PROGRAMMER

DUCC, UNIVERSITY OF DELHIDELHI-110007

E-mail: [email protected]@hotmail.com

Home page: http://people.du.ac.in/~ighani

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