INTRODUCTION TO COMPUTER

What is a Computer?
A computer is an electronic device that takes raw data as input, processes it under the control of set of instructions (called program) and gives the result (output) and the output is saved for the future use. A computer does both numerical and non-numerical (arithmetic and logical) calculations. The data is processed in binary form; according to instructions given to it in the program.A computer is a multi-function device, capable of carrying out a diverse set of functions. It can be used for typing documents, for sending email, and for browsing internet. It can also be used to handle spreadsheets, accounting, database management, presentations, games, and more.
The main unit inside a computer is the CPU (Central Processing Unit) that interprets and executes instructions. It controls all internal and external devices, in performing arithmetic and logic operations. The Electronic Numerical Integrator and Computer (ENIAC) was the first electronic computer which was developed in 1946 and weighed 30 tons and took 1,800 square feet space.
Hardware & Software
A computer is composed of hardware and software. It can be in a variety of sizes and configurations. A computer’s abilities can also be extended.
1. Hardware: The term hardware refers to the physical structure of the actual machinery which consists of wires, transistors, circuits, monitor, mouse, keyboard, etc. The functionality of a computer can be increased by adding new or improved parts to it e.g., the working memory (RAM) can be increased for making the machine run faster, a larger hard drive can be added which will allow more information to be stored.
2. Software: Software, are the computer programs which are used for different purposes. These are a set of instructions and data that tells the hardware what to do. It guides the hardware in accomplishing the task. Software is held either on the hard disk of computers, CD-ROM, DVD or on a diskette (floppy disk) and is loaded (i.e. copied) from the disk into the computers RAM (Random Access Memory). For extending computer’s capabilities, more programs can be installed e.g., a suitable desktop publishing program can be purchased and installed for making posters and cards, or a program for creating or editing sound files, can be installed .
Types of software:
1. System software:
a) Operating System Software: It consists of DOS, Windows XP, Windows Vista, Unix/Linux, MAC/OS X etc.
b) Utility Software: These are Windows Explorer, Windows Media Player, Anti-Virus Utilities, Disk Defragmentation, Disk Clean, Backup, WinZip, WinRAR etc…
2. Application software:
a) Package Software: These include Ms. Office 2003, Ms. Office 2007, Macromedia (Dreamweaver, Flash, and Freehand), Adobe (PageMaker, Photoshop)
b) Tailored or Custom Software: These include SAGE (Accounting), Galileo/Worlds pan (Travel) etc
Key Components of a Computer:
Though computers come in many different shapes and sizes, however, all computers are similar to each other and have the same basic components. Key components of a computer include:
1. Input Devices: Input devices allow the user to control the machine and helps him in directing computer the instructions what to do. The input device is the conduit through which data and instructions are entered in to computer. A keyboard and mouse are the standard way to interact with the computer. Common examples of input devices are: Mouse, Keyboard, Scanner, Digital / web Camera, Bar Code Reader, Microphone, Biometric Devices, etc. Other devices include joysticks and game pads used primarily for games.
2. Output Devices: Output devices tell the user about the activities which have been performed. These include Monitor, Printer, Projector, Speaker etc.
3. Peripherals: Peripherals are the devices for connecting to a computer and for performing specific tasks. For example, a printer, a scanner, a digital camera, modem etc., are peripherals. Other peripherals include alternative keyboards, switches and touch-screens etc. Peripherals are usually related to the input or output devices.
Modem: “Modulate/ Demodulate” is the device that converts the digital signals used inside the computer to an analogue or voice signal that are transmitted over the phone lines. The modem converts the signal back into a format that can be used by the receiving computer.
4. The Processor: It is the central processing unit (CPU) and the ‘brain’ of a computer for executing instructions. The CPU consists of a CU (Control Unit) and an ALU (Arithmetic Logic Unit). The control Unit (CU) directs and coordinates the operations of the entire computer. It obtains the instructions from RAM and stores in the instruction register.
Mathematical operations are performed by Arithmetic Logic Unit (ALU). The processor, either directly or indirectly, controls all the work carried out by the computer or follows the instructions provided to it by the input devices. The processor plays an important role in almost all aspects of the functioning of computers.
5. Memory: Memory is one of the most important elements of every computer. The computer memory is electronic circuitry that holds data and program instructions until it is processed. There are three types of computer memory which are RAM, CMOS, and ROM. For performing the tasks computers need working memory i.e. some short-term memory. It is known as random access memory (RAM). RAM is very important to the overall functioning of the computer as it enables a computer to store, at least temporarily, data, programs and also instructions. It consists of thousands of circuits. Each circuit holds one bit of data. The computer holds (stores) data in RAM and copies it to the CPU and from the CPU (processor) transfers it back to RAM. A system with a fast processor but with a small amount of RAM will not perform to its full potential, whereas, a slower processor with plenty of RAM would performs up to its full potential. When the processor turns into a “word processor”, the instructions for are copied from the disk to RAM. A 32 MB RAM indicates that it can hold 32 million bytes of data.
Complementary Metal Oxide Semiconductor (CMS) is a battery-powered chip that retains data relating to the computer configuration when the computer is turned off. Read Only Memory (ROM) is a set of chips that contain permanent instructions about the “boot process.”
6. The Hard Disk Drive: It is the main storage device of a computer which stores both the programs (soft ware) as well as the work created. It is the magnetic disk inside the machine which has long-term memory. The hard disk drive is formatted into the tracks, cylinders, sectors and groups of sectors. Tracks are concentric circles in a disk that hold the data. One can find out what he did a week ago or on a particular day.
Types of Computers:
On the basis of working principle, a computer can be classified as an Analogue computer, Digital Computer and Hybrid Computer.
a) Analogue Computer: An Analogue computer is a computer that uses continuously-changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities for solving the problem. Analog computers can have a very wide range of complexity.
b) Digital Computer: A computer that performs calculations and logical operations with quantities represented as digits (in the binary numbers). In digital computers, even letters, words and whole texts are represented digitally. Unlike analogue computers, digital computers can assess in arbitrarily small steps a large numbers of digits.
c) Hybrid Computer (Analogue + Digital): A Hybrid computer is a digital computer that accepts analogue signals, converts and processes them in digital form. The computer is capable of inputting and outputting in both digital and analogue signals. It accepts a varying input which is then converted into a set of discrete values for digital processing. A hybrid computer system offers a cost-effective method of performing complex simulations.
On the basis of Size
Super Computer: A supercomputer is typically used for scientific and engineering purposes. These computers require immense amounts of mathematical calculations. They are faster and expensive. They are used for weather forecasting for animated graphics, fluid dynamic calculations, nuclear energy research, petroleum exploration etc.
India's First Supercomputer was PARAM 8000 which was launched in 1991 with a rating of 1 Gigaflop (billion floating point operations per second). The computer was developed by Center for Development of Advanced Computing (C-DAC) in 1991, a department run by the government. PARAM stood for Parallel Machine. All the chips and other elements used in making PARAM were bought from the open domestic market. The major applications of PARAM Supercomputer are used in long-range weather forecasting, remote sensing, drug design and molecular modelling.
The speed of a supercomputer is measured in "FLOPS" i.e. FLoating Point Operations Per Second. This measurement is either quoted based on the theoretical floating point performance of a processor which is generally unachievable when running real workloads.
b) Mainframe Computer: It is a very large and expensive computer which can support thousands of users simultaneously. It is more powerful than a supercomputer as it can simultaneous support more programs. A mainframe computer is used for processing data by large organisations such as banks for controlling entire business operation. A mainframe is the central data repository or hub in the data processing center of a corporation and is linked to users through terminals.
Mainframe computers use proprietary operating systems, most of which are based on Unix, and a growing number on Linux. Centralisation of data in a single mainframe computer saves customers from managing updates of business data as the entire data is current and updated. In mainframe computers CU and ALU which were both separate units are now contained in the same chip from 1971. This was the beginning of the microprocessor era and PC computers.
c) Mini Computer: Mini computers are the one which are found between the main frame computers and the work station computers. It serves the same functions as the normal desktop computers. A mini computer is a multi processing system which is capable of supporting from 4 to about 200 users simultaneously. Mini computers are of different types having different hardware and software’s.
Difference between supercomputer and a mainframe computer:
The chief difference between a supercomputer and a mainframe computer is that a super computer has the power to execute programs at a faster speed, whereas a mainframe computer executes many programs simultaneously and handle very large databases or does a great amount of computation or both.
d) Micro Computer:
i). Desktop Computer: It is a personal or micro-mini computer sufficient to fit on a desk.
ii). Laptop Computer: A portable computer with an integrated screen and keyboard. It is smaller than a desktop computer and larger than a notebook computer.
iii). Palmtop Computer/Digital Diary /Notebook /PDAs: It is a hand-sized computer. Palmtops have no keyboard. The screen serves both as an input and output device.
iv).The iPad, a type of tablet computer:
Tablet Computers: A tablet computer is a complete mobile computer, larger than a mobile phone, integrated into a flat touch screen. The flat touch screen is operated by touching the screen. The touch-sensitive screen is used for typing and navigation and do not require a keyboard or mouse. Tablet computers are more portable than laptops. The iPad is an example of a tablet computer.
v).Mobile Phones: Many mobile phones can do a lot of things as a computer can do, such as browsing the internet or playing games. vi).Game Consoles: A game console is a specialized kind of computer that is used for playing video games.
vii).TVs: Many TVs now have applications that enables a person to access various types of online content.
Data Measurement and Data Carrying Devices:
What is Binary?
The word “binary” is a system that has only two possible digits. It is a numeric system which uses two numerals to represent all real numbers. While the decimal system uses ten numerals, binary uses only 0 and 1. Each digit in a binary number system represents a power of two. The first digit on the right represents the 0th power, the second represents the 1st power and the third represents the 2nd power, and so on so forth. For example number 31, is represented as 11111 = (16+8+4+2+1) or 50 is represented as 110010 (32+16+0+0+2+0). All computers work on a binary numbering system, i.e. they process data in one's or zeros.
The 1 or 0 level of storage is called a bit. A bit is a binary digit, the smallest data on a computer. A byte consists of eight bits. A kilobyte (KB) is 1,024 bytes. Computer storage and memory is often measured in megabytes (MB) and gigabytes (GB). In computer jargon the following units are used:
Unit Equivalent Equivalent
1 kilobyte (KB) 1,024 bytes
1 megabyte (MB) 1,048,576 bytes 1024 kilobytes
1 gigabyte (GB) 1,073,741,824bytes 1024 megabytes
1 terabyte (TB) 1,099,511,627,776 bytes 1024 gigabyte
1 petabyte (PB) 1,125,899,906,842,624 bytes 1024 terabyte
Booting: The boot process is a series of instructions from ROM that prepares the computer to perform its work. Booting is restarting computer after loading the system files of the operating system from the disk into the computer memory. There are two types of booting:
1.Cold Booting: It is restarting the computer by pressing the power switch ‘On’ i.e. turning from a powered-down state.
2.Warm Booting: It is restarting the computer without turning off power i.e. pressing the restart button when the computer is already on.
LAN: The local area network interconnects individual computers in a limited geographic area such as a home, school, computer laboratory, or office building and transfers data with very low error rates. LAN which was introduced in the 1970s has become widespread in commercial and academic environments. One LAN can be connected to other LANs over any distance via telephone lines and radio waves. Each individual computer in a LAN has its own CPU with which it executes programms. A user can share devices, such as laser printer, data and can communicate with each other by sending e-mail or engaging in chat sessions. The primary function of a Local Area Network is to share resources such as files, data, printing, mail, remote links, videos etc. LANs are capable of transmitting data at very fast speed much faster than through a telephone line. However, it has limited distances and there is also a limit on the number of computers that can be attached to a single LAN.Local area networks have several advantages of sharing hardware and software, disadvantages include complexity, maintenance costs. The weakest link is the network.
WAN: Wide Area Network (WAN) is connecting computers over a wider area (i.e. the whole world). Wide-Area Networks are commonly connected either through the Internet or special arrangements made with phone companies or other service providers. In a WAN, one network which may be anywhere in the globe can connect in different country. Messages can be sent very quickly to anyone else on the network. Files, data, messages with pictures, sounds, can be shared over a larger area. Printers or phone lines to the internet can be shared by all the computers on the network. Everyone on the network can use the same data. WAN are expensive and generally slow. They require a good firewall to restrict outsiders from entering and disrupting the network. Security is a real issue when many different people have the ability to use information from other computers. It is Vulnerable to hackers or other outside threats. The router (modem) connecting to Internet is often labeled as a WAN.
MAN: Metropolitan-Area Network is a network that is utilised across multiple buildings. It is much larger than the standard Local-Area Network but is not as large as a Wide Area Network. It is commonly used in school campuses and large companies with multiple buildings.
Wi-Fi: Wireless Fidelity is wireless networking technology that uses radio waves to provide wireless high-speed Internet and network connections. Wi-Fi is based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards." In Wi-Fi there is no physical wired connection between sender and receiver. Wi-Fi uses radio frequency (RF) technology, a frequency within the electromagnetic spectrum associated with radio wave propagation. When an RF current is supplied to an antenna, an electromagnetic field is created which enables to propagate through space.
Computer Virus: Viruses are small programs that hide themselves on your disks (both diskettes and your hard disk).Unless one uses virus detection software one would not know that there is a virus. viruses are activated in different ways.IT Act 2000 explains a computer virus as any computer instruction, information, data or programme that destroys, damages, degrades or adversely affects the performance of a computer resource or attaches itself to another computer resource and operates when a programme, data or instruction is executed or some other event takes place in that computer resource. (Chapter IX–Section 43 (III))
The worst thing about a computer virus is that they can spread from one computer to another, either via the use of infected floppy disk or over a computer network, including the Internet. Viruses hide on a disk and when one access the disk the virus program starts and infect computer and damage it. Under the IT Act 2000, damage means to destroy, alter, delete, add, modify or rearrange any computer resource by any means.(Chapter IX –Section 43 (IV)).
There are a number of third party antivirus products available for payment. Many companies supply updated disks on a regular basis or allow you to receive updates through an electronic, on-line bulletin board. The main thing about your virus checker is that it should be kept up to date.
What is a Satellite: A satellite in a geostationary orbit which revolves an equatorial orbit around the equator at the same angular velocity of the earth. The Earth rotates towards the east. The satellite rotates approximately 22,000 miles up 360 degrees every 24 hours in a fixed position? It remains over the same spot on the earth's surface at all times. It stays fixed in the sky from any point on the surface from which it can be "seen.” It is fixed to an earth-based observer. Satellites are used for diverse purposes for weather forecasting, television broadcast, amateur radio communications, Internet communications, and the Global Positioning System, (GPS).
Communications satellite: It is an artificial satellite stationed in space for the purpose of telecommunications. According to the type of orbit, there are three types of communications satellite systems. In a communications context a satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth.
Satellite Network: In a satellite Internet connection, data both out going and incoming (i.e. transmitting and receiving signals) are received through a satellite dish antenna which operates in the microwave portion of the radio spectrum. Satellite Internet systems are excellent for people in rural areas where Digital Subscriber Line (DSL) and cable modem connections are not available. Satellite connection is good for Web browsing and for downloading files. The two-way satellite Internet option offers an always-on connection that bypasses the dial-up process. In this respect, the satellite system resembles a cable modem Internet connection.
The services are provided to users world-wide through low Earth orbit (LEO) satellites. Geostationary satellites can offer higher data speeds, but their signals can not reach some polar regions of the world. A well-designed LEO system makes it possible for anyone to access the Internet via wireless from any point on the planet using an antenna. A low-earth-orbit (LEO) satellite system employs a large fleet of "birds," each in a circular orbit at a constant altitude of a few hundred miles. The fleet is arranged in such a way that, from any point on the surface at any time, at least one satellite is on a line of sight.
Very-small-aperture terminal (VSAT): VSAT (Very Small Aperture Terminal) is a satellite communications system that serves home and business users. A VSAT consists of two parts, a transceiver which receives or sends signal to a satellite transponder in the sky, which is placed outdoors for a line-of-sight to the satellite. The satellite sends and receives signals from an earth (ground) station computer that acts as a hub for the system. The indoor unit is a small desktop box that contains the receiver and transmitter boards and an interface to the user’s equipment. Each end user is interconnected with the hub station via the satellite. The hub controls the entire operation of the network. For one end user to communicate with another, each transmission has to first go to the hub station that then retransmits it via the satellite to the other end user's VSAT. VSAT can handle up to 56 Kbps.VSAT offers a number of advantages over terrestrial alternatives.
Hacking: According to the provisions of IT Act 2000, hacking is committed by a person when that person, with the intent of causing or knowing that he is likely to cause wrongful loss or damage to the public or any person, destroys or deletes or alters any information residing in a computer resource or diminishes its value or utility or affects it injuriously by any means. Punishment prescribed under section 66 of IT Act 2000 for hacking includes imprisonment up to three years or fine up Rs.Two lakhs or both. (Chapter XI – Section 66 (1&2)
Electronic Record: An electronic document is any document that is generated or stored on a computer, such as a letter, a contract, or a will. In addition, an electronic document can be an image, such as a blueprint, a survey plat, a drawing, or even a photograph. A Digital signature can be used to sign these documents. IT Act defines electronic record as "data, record or data generated, image or sound stored, received or sent in an electronic form or micro film or computer generated micro fiche". (Chapter I – Section 2 (t))