Transaction Security

An online transaction requires a consumer to disclose sensitive information to the vendor in order to make a purchase, placing him-self at significant risk.  Transaction Security is concerned with providing privacy in transactions to the buyers and sellers and protecting the client-server network from breakdowns and third party attacks. It basically deals with –

• Client security – Techniques and practices that protect user privacy and integrity of the computing system.
• Server security – Protect web server, software and associated hardware from break-ins, vandalism and DOS attacks.
• Secure transactions – Guarantee protection against eavesdropping and intentional message modification (tapping, intercepting, diverting)

Security Issues in E Commerce 

1. Malicious Code – It includes a variety of threats such as virus, worms, Trojan horse etc.

• Virus – A virus is a computer programme that has the ability to replicate itself and spread to other files, deliver a pay load include micro virus, script virus, file infecting virus
• Worms – It is a virus designed to spread from computer to computer.
• Trojan horse – It appears to be a benign, but does something other than expected. It is often a way for a virus to enter a computer.

2. Unwanted programmes – There are programmes installed without the users consent.

• Browser parasites – Programmes used to monitor and change settings of a user`s browser
• Adware – Unwanted pop up ads
• Spyware – Programmes used to obtain personal information

3. Phishing and Identity theft – It refers to any deceptive, online attempt by a third party to obtain confidential information for a financial again.

4. Hacking – 

• Hacker – An individual who intends to gain unauthorised access to computer systems.
• Cracker – A hacker with a criminal intent
• Cyber Vandalism – Intentionally, disrupting, defacing or destroying a website

5. Credit Card Fraud – It refers to use of stolen data to establish credit under false identity.

6. Spoofing – Hackers hide their identity, misrepresent themselves by using fake email addresses or masquerading as someone else this threatens integrity and authenticity of the hacked website

7. DOS (Denial of Service) – Hackers flood a website with useless traffic to inundate or overwhelm the network.

8. DDOS (Distributed Denial of Service) – Hackers use numerous networks from numerous launch points to send useless traffic to a website. This may cause a complete shutdown making it impossible for users to access the website.

9. Sniffing – A sniffer is a type of eavesdropping application that monitors information travelling over the network. It enables hackers to steal proprietary information from anywhere on a network including email, files, reports etc.

10. Insider jobs – It involves poorly designed server and client software and complexity of programmes which increase vulnerabilities for hackers to exploit.

Defensive measures against Security Issues in E commerce →

The defensive measures used in Transaction Security are: 

1. Encryption – It is the process of transforming plain text or data into cipher text that cannot be read by anyone except the sender and receiver. It is done with a help of mathematical algorithm the key is required to decode the message.

In an Asymmetric Key Encryption both the sender and receiver use the same key to encrypt and decrypt the messages while Symmetric or Public key encryption uses two mathematically related digital keys which are public key and private key to encrypt and decrypt the messages.

2. Secure Socket Layer – The SSL protocol provides data encryption, server authentication, client authentication and message integrity for TCP/IP connections. It prevents eavesdropping, tampering or forgery when data is transported over the internet between two applications.

3. Secure hypertext transfer protocol – It is a secure message oriented communication protocol designed for use in conjunction with HTTP enabled secure connection and individual message transmission. Under SHTP a message may be signed, authenticated or encrypted.

4. Trust Seal Programmes – Trust seals have been developed to provide assurance about web businesses practices and policies.

5. Digital Signature – It is a signature in encrypted electronic code which is encrypted by the sender with his public key and can be decrypted only with the public key of the sender (by receiver).

6. Digital Certificate – It is a digital document issued by a trusted third party institution known as certificate authority that certifies the name and identifying information of the company. It is signed with the private key of the Certificate Authority. Therefore its authenticity can be known by knowing the public key.

A digital certificate contains the following information:

• The name of the company
• Public key of the company
• Digital Certificate serial number
• Expiry date/Date of Issue
• Digital Signature of the Certificate Authority

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In the computing world Firewall is a software or hardware based network security system that controls incoming and outgoing network traffic by analysing data packets and determining whether they should be allowed through or not based on a certain rule set. It can have a variety of configuration depending upon the user requirement. It builds a bridge between internal and external network and protects against →

• Remote login
• Application back doors
• Virus, spam, malware etc.

 A Firewall accomplishes controlled access using –

• Packet filtering
• Circuit level gateway
• Application level gateway
• Stateful inspection

Types of Firewall

On the basis of Traffic controlling technique Firewall can be categorised into the following four:

Packet Filtering Firewall – It operates by filtering the incoming and outgoing packets using routers or devices that have been configured to screen.

It examines the information contained in TCP and IP packet headers, in order to accept or deny packets from entering or leaving the network.  It checks the following attributes –

• Source address
• Destination address
• Application or protocol
• Source port number
• Destination port number

Circuit Level Firewall – Along with allowing or disallowing packets a Circuit Level Firewall also determines whether the connection between both ends is valid. It validates each session of established connection for exchange of data and monitors TCP handshaking.

It also checks connection request attributes against configured filtering rules and then traffic is filtered based on specified session rules. It checks for the following –

• Destination of IP address / Port
• Source of IP address / Port
• Time of day
• Protocol
• User
• Password

Application Level gateway – An Application Level gateway is similar to circuit level gateways but is application specific i.e. it can filter packets at the application layer of the OSI model. Incoming or outgoing packets are unable to access services for which there is no proxy. Therefore, it is also called proxies. It can also be used to log user activity and logins. They can also filter application specific commands.

Stateful Multilayer Inspection – Such a firewall is the combination of all the three. Traffic is filtered based on specific application rules, such as specified app, browser or protocol (FTP) or combinations. It filters packets at network layer which determines whether a session is legitimate or not and then evaluates the contents of the packet at application layer.

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Wireless networks like GSM, CDMA, TDMA, GPRS and UMTS enables a user of a mobile device to access a variety of information stored on databases of connectivity providers, information providers, service providers and web servers.

Mobile devices refer to devices that connect to a wireless network and are capable of accessing, interacting and displaying information on screen eg. –

1. Cellular phones or Smart phones
2. Pager devices
3. Handheld computers, palmtops, tablets
4. Laptop
5. Personal digital Assistants (PDA)

The main idea behind M commerce is to enable various applications and services available on the internet to portable devices (mobile phones, tablets, laptops etc.) to overcome the constraints of a desktop computer. M commerce aims to serve all information and material needs of the people in a convenient and easy way.

Applications of M commerce

• Mobile connect time communications
• Mobile equipment and device providers
• Value added services
• Mobile application developers
• Mobile commerce application providers
• Mobile Shopping
• Mobile advertising
• Mobile auctions
• Mobile entertainment
• Mobile financial services
• Location and search service

Advantages of M commerce

• It provides a convenient, secure and easy to use communication and distribution network
• It provides a wider reach as most people use cell phones
• It enables a business to target customers effectively e.g. on the basis of location, service provider, devices etc.
• It reduces transaction and order processing cost
• It encourages competitive pricing
• It streamlines all business processes

Disadvantages of M commerce

• Low acceptance rate of new devices, applications and technology among people
• Lack of supporting infrastructure, professionals and technology in developing countries
• Security and privacy issues
• Expensive 2G, 3G plans
• Customer retention rate is very low

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Internet is a global system of interconnected computer networks that use standard internet protocol suite to kink several devices worldwide. It is an international network of networks, linked by optical, wireless and electronic networking technologies which consists of business, public, educational and government networks.

It carries an extensive range of information, resources and services. It utilises –

• IP Addressing Scheme
• Transmission Control Protocol (TCP)
• Peer2Peer (P2P) networks for file sharing and telephony

The main reasons for its establishment was to transmit data, share resources and communicate remotely.

Important Features –

• It is spread over 65 Countries
• There is no regulatory authority for internet therefore any one can access it
• All computers on the internet communicate via IP/TCP protocol using a client/server architecture
• A PC, Router, Browser and an Internet service provider are needed to connect to the Internet
• The main uses are –File sharing, Program sharing, Hardware sharing, Multi-user activities, Communication and Reaching remote areas

• It provides a variety of services such as – File Transfer, Electronic mail, Real-time broadcasting, E-commerce, Information resources etc.
  

Applications of Internet –

• Communication – Email, Online chat, Telephony (Voice, fax, SMS, MMS), video conferencing, file sharing etc.
• Remote login – A user can login to his/her concerned online account from anywhere in the world.
• E-commerce – B2B, B2C, C2C portals,
• Online Banking – Electronic fund transfer, Online account management
• Entertainment – Movies, videos, online books, news etc.
• Advertising – Banner ads, text ads, social media marketing etc.
• Research and Development – Online surveys, private browsers, search engines
• Online Education & Training – Online exams, tutorials, e-books, notes and lectures etc.
• Stock Exchange and Trading
• Social Networking and Blogging

Disadvantages –

• Cyber Crime
• Virus, Malware, Spamming
• Phishing
• Hacking
• Adult and abusive content
• Unrestricted medium
• Theft of personal information and copyright issues
• Online Fraud and terrorism

What is Extranet?

An extranet is a private network that uses Internet technology and the public telecommunication system to securely share part of a business’s information or operations with suppliers, vendors, partners, customers, or other businesses. An extranet can be viewed as part of a company’s intranet that is extended to users outside the company. It has also been described as a “state of mind” in which the Internet is perceived as a way to do business with other companies as well as to sell products to customers.

It is an extension of info system of the company to its partners outside.  It uses internet protocols to link intranets over the public internet.  It involve authentication via a username and password.

Uses of Extranet-

• Exchange large volume of data
• Share product catalogues
• Collaborate with partners & peers
• Joint training programs

What is Intranet ?

An intranet is a private network that is contained within an enterprise. It may consist of many interlinked local area networks and also use leased lines in the wide area network. Typically, an intranet includes connections through one or more gateway computers to the outside Internet. The main purpose of an intranet is to share company information and computing resources among employees. An intranet can also be used to facilitate working in groups and for teleconferences.

Typically, larger enterprises allow users within their intranet to access the public internet through firewall servers that have the ability to screen messages in both directions so that company security is maintained. When intranet is made accessible to customers, partners, suppliers, or others outside the company, it becomes an extranet.

It enhances existing communication between employees and provides a common knowledge and storage base.  It provides access to company, data systems, technical documents etc.

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An information system can be defined as a set of interrelated components that collect (or retrieve), process, store, and distribute information to support decision making and control in an organization. In addition to supporting decision making, coordination, and control, information systems may also help managers and workers analyse problems, visualize complex subjects, and create new products.

Components of Information System:

(1) People Resource: People are considered part of the system because without them, systems would not operate correctly. In Information system there are two kinds of people resource –

 (i) End User: also called users or clients, are people who actually use the information system or its products. Eg. Customers, salesperson, engineers, clerks, managers

 (ii) IS Specialist: also called IS developers, are people who develop the information system and its components. Eg. System Analysts (who design IS based of requirements of end users), Software developers (create computer programs based on specifications of analysts), System Operator (who help monitor and operate large computer system and networks) and other Managerial, Technical, Clerical IS personnel.

(2) Hardware Resource: All physical and tangible devices or material used in information processing. e.g.

 (i) Computer Systems: It consists of the central processing units and interconnect peripheral devices. Eg. Handheld devices, laptops, desktops, large mainframes computers

 (ii) Computer Peripherals: input and output devices such as keyboard, mouse, printer, monitor, disk drive, etc.

(3) Software Resource: It includes set of operating instructions called programs, which direct and control computer hardware and set of information processing instructions called procedures that people need. Hardware resources need programs and procedures in order to properly collect, process and disseminate information to their users.

Examples:

 (i) System Software: such as an operating system. It controls and supports the operations of a computer system.

 (ii) Application Software: which are programs that directly processing for a particular use of computers by end users. e.g. Sales analysis programs, a payroll program, a ward program, etc.

 (iii) Procedures: Instructions for people who will use the IS. Eg. instructions for filling out a paper form.

(4) Data Resource: Data resources include data (which is raw material of information systems) and database. Data can take many forms, including traditional alphanumeric data, composed of numbers and alphabetical and other characters that describe business transactions and other events and entities. Text data, consisting of sentences and paragraphs used in written communications; image data, such as graphic shapes and figures; and audio data, the human voice and other sounds, are also important forms of data.

Data resources must meet the following criteria:

• Comprehensiveness: It means that all the data about the subject are actually present in the database.
• Non-redundancy: It means that each individual piece of data exists only once in the database.
• Appropriate structure: It means that the data are stored in such a way as to minimize the cost of expected processing and storage.

 The data resources of IS are typically organized into:

• Processed and organized data – Databases
• Knowledge in a variety of forms such as facts, rules, and case examples about successful business practices

(5) Network Resources: Telecommunications networks like the Internet, intranets, and extranets have become essential to the successful operations of all types of organizations and their computer-based information systems. Telecommunications networks consist of computers, communications processors, and other devices interconnected by communications media and controlled by communications software. The concept of Network Resources emphasizes that communications networks are a fundamental resource component of all information systems.

 Network resources include:

• Communications media: such as twisted pair wire, coaxial cable, fiber-optic cable, microwave systems, and communication satellite systems.
• Network support/infrastructure: This generic category includes all of the people, hardware, software, and data resources that directly support the operation and use of a communications network. Examples include communications control software such as network operating systems and Internet packages.

Types of Information System:

(1) Management Support System – When Information Systems`s focus on providing information and support for effective decision making by managers it is called a Management Support System.

Types of Management Support System:-

 (i) Management Information System (MIS): It provides information in form of reports and displays to managers and other business professionals.

Example, Sales Manager may use this computer to instantaneously display sales result of their product and access their corporate intranet for daily sales analysis report that evaluate sales made by each sales person.

(ii) Decision Support System (DSS): It gives direct support to managers during decision making process. It tests alternative solutions and selects the better option. Example, A product manager may use DSS to decide how much product to manufacture based on expected sales associated with future promotion and availability of raw material.

Uses: Logistics, Financial Planning, Group decision support

(iii) Executive Information System (EIS): It provides critical information from wide variety of internal and external sources in easy-to-use form to executives and managers. They measure Critical Success Indicators (CSI) and Key Performance Indicators (KPI) associated with the problem to provide valuable information.

(2) Operations Support System – The Role of OSS is to efficiently process business transactions, control industrial processes, support enterprise communications and collaborations, and updates corporate databases.

Types of Operational Support System:-

(i) Transaction Processing System: It records and process data resulting from business transactions. It processes transactions in two ways –

a.) Batch Processing – transactions are accumulated over a period of time and processed periodically.

b.) Real Time – transaction is processed immediately after a transaction occurs.

Uses: Sales software at many retail stores, Order Processing, Payroll Management etc.

(ii) Process Control System: It monitors and controls physical processes. It tells the user about change in variables related to a process for effective performance evaluation and decision making. Example, petroleum refinery uses electronic sensors linked to computers to continuously monitor and control chemical processes.

Uses: Sensors, Auto-inventory reorder

(iii) Enterprise Collaboration System: These help to enhance team and workgroup communications and productivity in an organization. It includes applications that are sometimes called office automation systems. Example, video conference of a product design team (virtual team).

Uses: Communicating ideas, Share resources and Coordinate corporative work efforts

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Hardware 

Hardware refers to all devices that are physically connected to a computer i.e. something that can be physically touched. Without any hardware, software would have nothing to run on.

Hardware is the physical part of a computer which includes the digital circuitry as distinguished from the computer software that only executes within the hardware. It starts functioning once software is loaded on it.

Hence, the input device, storage, output devices are hardware.

Software

It is a general term used to describe a collection of computer programs, procedure and documentation that performs a series of task on a system. It is an ordered sequence of instructions for changing the state of computer hardware in a particular sequence. It is usually written in High level programing languages that are easier and efficient for humans to use and understand.

Software refers to planned step by step instructions required to convert data into information.

It may be classified as:

• System software
• Application Software
• Utility software
• Firmware
• Shareware

(1) System Software 

• It is a set of one or more programs designed to control the operation and extent of processing capabilities of a computer system.
• It supports the development and execution of other applications software
• It monitors the effective use of various hardware resources such as CPU, memory, peripherals
• It communicates with and controls the operation of peripheral devices

Types – Operating System, Device drivers, Language Translators, System Utility Programs, Communication software

(2) Application Software – It is set of one or more programs, designed to solve a specific problem or perform a specific task.

There are various application software like:

• Word processing Software
• Spread sheet Software
• Database Software
• Graphics Software
• Personal Assistance Software
• Educational Software
• Entertainment Software

 (3) Utility Software – This is a connection link between system software and application software. These are used as specific tools to develop any program, to perform any task etc.

(4) Shareware – It is a public-domain software also known as shareware. They are available for free, or for a nominal charge. They can be downloaded and used immediately from the internet by anyone. A Shareware may or may have not developed by professionals and are not tested professionally for user usage. The main con of such software is that bug fixing may never take place in case of some software.

(5) Firmware – It refers to a sequence of instructions, which is substituted for hardware and stored in the read only memory. With the advancement in technology, now software is made available on ROM chips to reduce hardware cost. ROM chips can be easily plugged into the computer system, and they form a part of the hardware.

Storage Devices 

Computers are used for immediate data processing as well as for storing large volumes of data for future purposes. Therefore a computer uses two types of memory i.e. Main/Primary memory and Secondary memory.

The Storage location where the data is temporarily stored is called primary memory while secondary memory is the storage location where programs and data are permanently stored for future use.

The data and instructions stored in the primary memory can be directly accessed by the CPU, however information stored in the secondary memory has to be transferred to the primary memory with help of Input/output devices and is then sent to the CPU.

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Microsoft Word is a widely used commercial word processor designed by Microsoft. It is a paid software that helps in preparing, editing, storing and printing documents quickly and with accuracy.

MS Word is a part of the Microsoft Office suite, a productivity software and can also be purchased as a stand-alone product. It was initially launched in 1983 and has been revised numerous times since then. MS Word is available on both Windows and Macintosh operating systems.

A word processor lets a user change words or phrases, move whole sections of text from one place to another, store blocks of text, align margins. Use of MS Word has changed the look and feel of official correspondence, reports, and proposals etc. to a great extent. The powerful features of Word supports to creation of graphic based multi-column publications such as Fliers, Newsletters and Internet web pages.

MS Word offers several features to ease document creation and editing including:

• WYSIWYG (what-you-see-is-what-you-get) display: It ensures that everything you see on screen will appear the same way when printed or moved to another format or program.
• Proof Reading – Spelling and Grammar check: Word comes with a built-in dictionary for spell checking; misspelled words are marked with a red underline.
• Text-level features such as bold, underline, italic and strike-through
• Page-level features such as indentation, paragraphing and justification
• Word Wrapping
• Selecting a block of Text
• Copy, Move, Paste and Cut Text
• Search And Replace Text
• Margin and Colum Settings
• Character Formatting and Styling
• External support: Word is compatible with many other programs, the most common being the other members of the Office suite

The default file format was .doc prior to the MS Word 2007 version; in 2007, .docx became the default file format.

MS-Excel

Microsoft Excel is a software program developed by Microsoft Corp. that allows users to organize, format and calculate data with formulas using a spread sheet system. This software is a part of the Microsoft office suite and is compatible with other applications of the office suite.

Excel has the same basic features as every other spread sheet, and uses a collection of cells arranged into rows and columns to organize data. They also display data as charts, histograms and line graphs. An Excel document is called a Workbook. A workbook always has at least one Worksheet. Worksheets are the grid where a user can store and calculate data. A user can have many worksheets stored inside a workbook, each with a unique worksheet name.

Excel is used widely in most finance-related activity. The ability to create new spread sheets where users can define custom formulas to calculate anything from a simple quarterly forecast to a full corporate annual report makes Excel highly appealing.

Excel is a useful tool for scientific and statistical analysis with large data sets. Excel’s statistical formulas and graphing can help researches perform variance analysis, chi-square testing, and chart complex data.

Applications of MS Excel:

• Preparation of Annual Budgets
• Preparation of Annual Reports
• Preparation of Income Statement
• Accounts Payable/Receivable
• Payrolls and Invoice
• Inventory Control

MS-PowerPoint

PowerPoint is a presentation program developed by Microsoft Corp. This software allows users to create anything from basic slide shows to complex presentations.

PowerPoint is a tool used to communicate your ideas effectively through visual aids that look professionally designed and yet are easy to make.

PowerPoint is often used to create business presentations, but can also be used for educational or informational purposes. The presentations are comprised of slides, which may contain text, images, and other media, such as audio clips and movies. Sound effects and animated transitions can also be included to add extra appeal to the presentation. The design features of PowerPoint support customization of the appearance and format of the slides. PowerPoint comes with a set of preloaded themes or templates to choose that range from simple colour changes to complete format layouts. Apart from these it also includes all basic text editing and styling options.

The default file format was .ppt prior to the Microsoft PowerPoint 2007 version; in 2007, .pptx became the default file format. Also extensions .pps (before Microsoft PowerPoint 2007) and .ppsx (Microsoft PowerPoint 2007 onwards) can be used for opening presentations in Slide Show view instead of in Normal view.

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Machine Language is the language written as strings of binary 1`s and 0`s. It is the only language which a computer understands without using a translation program.

A machine language instruction has two parts. The first part is the operation code which tells the computer what function to perform and the second part is the operand which tells the computer where to find or store the data which is to be manipulated. A programmer needs to write numeric codes for the instruction and storage location of data.

Disadvantages –

• It is machine dependant i.e. it differs from computer to computer.
• It is difficult to program and write
• It is prone to errors
• It is difficult to modify

Assembly Language

It is a low level programming language that allows a user to write a program using alphanumeric mnemonic codes, instead of numeric codes for a set of instructions.

It requires a translator known as assembler to convert assembly language into machine language so that it can be understood by the computer. It is easier to remember and write than machine language.

Assembler – It is a computer program which converts or translates assembly language into machine language. It assembles the machine language program in the main memory of the computer and makes it ready for execution.

Advantages –

• It is easy to understand and use
• It is easy to locate and correct errors
• It is easier to modify

Disadvantages –

• It is machine dependant

High level Language

It is a machine independent language. It enables a user to write programs in a language which resembles English words and familiar mathematical symbols. COBOL was the first high level language developed for business.

Each statement in a high level language is a micro instruction which is translated into several machine language instructions.

A compiler is a translator program which translates a high level programming language into equivalent machine language programs. It compiles a set of machine language instructions for every high level language program.

Source code: It is the input or the programming instructor of a procedural language.

The compiler translates the source code into machine level language which is known as object code. Object code can be saved and executed as and when desired by the user.

Source Code   →  Language Translator Program  →    Object code

High level language                   →                   Machine level language

Linker: A program used with a compiler to provide links to the libraries needed for an executable program. It takes one or more object code generated by a compiler and combines them into a single executable program.

Interpreter: It is a translator used for translating high level language into the desired output. It takes one statement, translates it into machine language instructions and then immediately executes the result. Its output is the result of program execution.

Advantages of High level Language –

• It is machine independent
• It is easier to learn and use
• It is easier to maintain and gives few errors

Disadvantages –

• It lowers efficiency
• It is less flexible

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A Computer system includes the computer along with software and hardware that are necessary to operate a computer.

The word computer comes from the word “compute” which means to calculate.

A computer may be defined as an electronic device, which can store and manipulate data and provide result according to instructions fed by the user. A computer does this by performing arithmetic and logical operation at an enormous speed.

Data: A data is a raw fact, figure or a symbol.

Information: Organized, meaningful and useful data is known as Information.

A computer captures the input data, then manipulates it and then manages the output result as and when required. Therefore it is also known as a data processor. The activity of processing data using a computer is called data processing.

Characteristics of a Computer:-

Automatic and Electronic – Computers are automated machines which requires no human intervention to carry out its work.

Speed- It works at an enormous speed. It can execute about 3-4 million instructions per second.

Accuracy – It provides results based on the instructions fed by a user. An inaccurate result can only be due to incorrect input by a human. Computer errors caused due to incorrect input data are referred to as garbage-in-garbage out.

Diligence – A computer is free from monotony or fatigue. It can work continuously for hours with the same level of accuracy and efficiency.

Versatility – It performs a variety of arithmetic, non-arithmetic and logical operations at high speed. 

Storage or memory – It can store huge amounts of data which can be retrieved any time as and when desired by the user.

No I.Q. or Feelings – A computer is a user controlled machine and has no IQ or feelings. Therefore it cannot give bias results and cannot take an action on its own.

Components of a Computer:

People: Humans who operate the computer and feed instructions.

Data: Raw facts or figures that are fed to the computer as input by the user.

Hardware: The physical components which can be felt and touched in a computer.

Software: It refers to set of instructions or programs that are fed by the user to the computer system to get desired output.

Components of a computer system

(1) Input Unit – The input unit is used to give instructions/input data to the computer system. An input device accepts the instructions and data from the user, converts it into computer acceptable form and then supplies the converted data back to the computer system for further processing. Eg. Keyboard, Mouse, Camera, Touchscreen etc.

(2) Output Unit – Output unit is used to see the processed information. Output devices supply information to the user in variety of forms. It may be binary numbers, characters, text, images or videos. An output unit converts the processed input data into human readable form and displays results as and when desired by the user. Eg. Monitor, Printer, Projectors etc.

(3) Central Processing Unit (CPU) – CPU is the brain of the computer. It is the electronic circuitry within a computer which performs basic arithmetic, logical and control operations to carry out instructions fed by the user. A CPU has three parts –

Control Unit – The control unit is responsible for the control and coordination of the operations of a computer system. It accepts instructions from the main memory, interprets them and processes them for execution by different parts of a computer in a logical sequence. It receives and sends instructions from/to different parts of the computer in order to control them.

Arithmetic and Logical Unit (ALU) – Data provided by input devices is sent to the ALU from the main memory to make calculations and comparisons and the results are sent back to the main memory.

Registers – Temporary registers also known as scratch pads are used to store data which is frequently and repetitively used by the ALU. It prevents wasteful communication between the ALU and the main memory and saves time.

(4) Memory unit – All the data and information entered into a computer is stored in the memory unit. Computer memory can be Main/primary or secondary. When the information is to be stored permanently on a system, secondary memory is used and when the system stores the data (and sends it to the CPU) for the purpose of processing it is done in Main/primary memory. The major difference is that the data stored in the main memory cannot be accessed once a computer is switched off but information stored in the secondary memory can be retrieved even after the computer has been switched off.

Classification of Computers

i) Classification based on Operating Principles

Analog Computer: A computer which can measure changes in a continuous physical and electrical state such as pressure, temperature, voltage, length etc. It is generally used for scientific and engineering purposes. Eg: Car Speedometer

Digital Computer: A computer which represents data by “ON” and “OFF” status is called a digital computer. It converts data into binary form in order to process it. It is used in data processing activities.

Hybrid Computer: These are computers which are a combination of both analog and digital computers.

ii) Classification According To Purpose

Special purpose computers: Computers which are designed to perform some specific task or job .For example, computers used for weather forecasting satellite launching medical diagnostics are special purpose computers.

General purpose computers: Computers which are designed, not to perform only specific tasks, instead they are designed to handle a variety of applications for example, computers used in schools, colleges and offices are general purpose computers.

iii) Classification based on size and Capability

Micro Computers: A microcomputer is the smallest general purpose processing system. It is a digital computer whose processing unit consists of one or more microprocessors, one or more input / output units and sufficient memory to execute instructions. They are used in schools, homes, office etc. E.g. Desktops, laptops, etc

Minicomputer: A minicomputer is a medium-sized computer. That is more powerful than a microcomputer. These computers are usually designed to serve multiple users simultaneously (Parallel Processing). They are more expensive than microcomputers.

Mainframe computers: Computers with large storage capacities and very high speed of processing (compared to mini- or microcomputers) are known as mainframe computers. They support a large number of terminals for simultaneous use by a number of users like ATM transactions. They are also used as central host computers in distributed data processing system.

Supercomputer: Supercomputers have extremely large storage capacity and computing speeds which are many times faster than other computers. A supercomputer can execute about ten million Instructions per second. The supercomputer is mainly used for large scale problems in scientific and engineering purposes like as Weather analysis, CAD(computer aided designing) etc.

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