Introduction

The word "computer" is derived from the Latin word "computare". Which means to calculate, basically computer defined as one, which computes.Computer is an electronic device, which can perform certain mathematical calculations and logical operation at a very high speed. A computer is composed of hardware and software and can exist in a variety of sizes and configurations.

                       In another words, a computer is an electronic machine that helps us to solve the problems. It can be programmed to accept data (input) Process it into useful information (output) and store it away (in a secondary storage device) for safekeeping of later use. The working principle of computer can be summarized as input, process and output cycle. A computer system accepts instruction and data as input form some input devices keyboard, scanner, digital/web camera ,mouse, joystick etc,are some of the input devices.Those data are processed as per the instruction and finally the result is obtained in a output device. It is totally internal process of the computer system; CPU is the main processing device. After processing the data may be stored future use and can be retrieved whenever required. Monitor (screen) and Printer are the major output devices.

Software/Hardware

All of the components of a computer system can be summarized with the simple equations:

                 Computer System=Hardware+Software+Humaware

·                     Hardware - All physical parts of the computer which can touch and seen are known as Hardware.

·                     Software - All programs are known as Software.

·                     Human ware - User

Hardware: The physical components of a computer are called hardware. Computer hardware consists of those components which can be touched and felt. It is just the mechanical parts of Computer. For example the following are the major hardware components: Monitor, Keyboard, Printer, Mouse.Microprocessor, CPU, Hard Disk, Motherboard, Floppy Disk etc.

Software: Simply all the programs of computer are called software. The instructions given to the complain in the form of a program is called software. Software is the set of programs, which are to be installed in computer. With the help of software we can work in the computer. They are used to run and manage the computer where computer system is only possible, when we keep the software inside it.

Keyboard

Keyboard is the most common, familiar and most important input device. It looks like a typewriter. It has got various keys, which are used to give data and commands to the computer. Commonly, we use a standard QWERTY keyboard with letters arranged in the same order as those on a typewriter.

            The most important thing to watch out is the keyboard connector. If you build an ATX system, you'll need one with a DIN connector.

             A typical computer keyboard contains all letters, numbers, symbols of a regular typewriter, plus other keys which may include.

Number Keys: These are used for numerical calculation. It contains 0 to 9 and some numerical operators like +, - , *, / etc.

Functions keys to (F1 – F2): There are used to perform a set of calculation (mostly to give the commands to commands to the computer) by a single keystroke.

Special Key: The special keys are used to specific tasks. Some of the special keys are Enter, Backspace, Del, ALT, CTRL etc.

Enter: It is of the most important key on the keyboard. It is used to change the paragraph and to write the short text. It is also used to enter into the selected computer program by pressing it once.

Backspace: It is used to delete one character to the left of cursor.

Del: It is used to delete one character to the right of cursor. It is also used to delete the computer items.

Shift:  It is used to capitalize the letters and write upper printed characters on every key.

ESC: It is used to close the dialog boxes and also to terminate the running process.

ALT: It is used to activate the menu bar and to close the current window with the help of some other keys. It also used to define shortcuts for the computer application.

Ctrl: Mainly it is used for shortcut keys to perform specific task inside the computer programs. It is also used to define shortcuts.

Win Key: It is used to activate the START button.

Mouse

The mouse is yet another popular input device. The mouse is an input device that is used to give the command and sometimes input to the computer. A mouse is a small box with around ball at the bottom and with two or more depression switches at the top. A mouse enables the user to manipulate a pointer that moves on the screen.

According to the working principle, mouse can be divided into three categories.

 



Serial Mouse: A serial mouse is connecting to either COM1 or COM2, i.e.  And one of the available serial port on the computer. Connecting a serial mouse is very easy as one need to just plug in the connector attached to the mouse wire to vacant serial port on the computer. It has 9 pin and D type in shape.

 
  PS/2: Another way of connecting the mouse to a computer known as Bus connection. The other common type of mouse is a PS/2 mouse, which plugs into a PS/2 mouse port. Only differences between a bus mouse and a serial mouse is a serial mouse is connected to a serial interface card or same type of I/O card with a serial interface option. This interface was introduced with the IBM PS/2 series of computer, and was therefore, called PS/2. IT has 6 pin and circular type in shape.

  USB Mouse: USB mouse connects to USB port. USB stands for Universal Serial Bus, an external bus standard that supports data transfer rate of 12 Mbps. A single USB port can be used to connect up to 127 peripheral devices. USB also supports Plug-and-play installation and hot plugging.

Wireless Mouse: In this type of mouse everything is similar to conventional mouse except that no cable is used to connect the mouse to the computer system. Cordless (wireless) mouse isn't physically connected at all. Instead they rely on infrared or radio waves to communicate with the computer. Wireless mouse is more expensive than a both serial and bus mouse, but they do eliminate the cord, which can sometimes get in the way.

               In this type of mouse, everything is similar to conventional mouse except that no cable is used to connect the mouse to the computer system.

CPU

The main unit inside the computer is CPU. CPU stands for ' Central Processing Unit ' and it is the brain of computer. Without CPU there is nothing. This unit is responsible for all events inside the computer. It controls every internal and external devices, performs arithmetic and logic operations. The CPU consists of electronic circuits that interpret and execute instructions; it communicates with the input, output, and storage devices. The CPU with the help of memory executes instructions in the repetition of machine cycles. Most CPU's today are made by Intel and bear such names as ' Pentium Pro', ' Pentium II '. 'Pentium III ' and ' Pentium 4 '. Older Intel CPU's include the 80486 and 80386 families. Other Manufacturers also make CPU's: Motorola for Macintosh, AMD and Cirrus for PC's and others. The Speed of a CPU's is measured in megahertz.

The CPU is composed of main two units

The Control Unit (CU)

Directs and controls the activities of the internal and external devices. It interprets the instructions obtained into the computer, determines what data are needed, where it is stored, where  to store the results of the operation, and sends the control signals to the devices involved in the execution of instructions.

The Arithmetic and Logic Unit (ALU)

 Is the part where actual computations take place. It consists of circuits, which perform arithmetic operations (e.g. addition, subtraction, multiplication, division) over data received from memory and capable to compare numbers.

Computer Generation

Scientist categorized computers in five generation depending on the technology, speed, languages, processing, devices etc. In the development of a computer there is lot of changes from 1946 to 1990. This time is divided in different generations by scientists in a conference in 1962.

First Generation (1946-1958): The first generation computer used vacuum tubes as the major storage element, they also consisted mercury delay line for storage such first generation computers are EDSAC.

Second Generation (1959-1964): When the semiconductor transistor replaced the vacuum tube that has a lot of changes in second generations. 1000 vacuum tubes work could do 1 transistor. Computer size and speed is more reliable than first generation computer.

 




Third Generation (1965-1974)By the development of a small chip consisting of capacity of the 300 transistors called integrated Chip(IC). They were very smaller in size and higher efficiency in speed & memory capacity.:

Fourth Generation (1975-1990): Very soon ICS were replaced by LSI. In this generation scientist use LSI and VLSI most commonly known as microprocessors. The world first microprocessor INTEL-4004 was produced in 1971 and used in this generation computer.

Fifth Generation (1991- Present): The fifth generations computers are underdevelopment stage. These computers are being made using microprocessors and will used USLI chips in the future. It is estimated that these computers of fifth generation will have an artificial intelligence with a little thinking capacity and they will understand the natural languages like English, Japanese etc.

Uses of computer

Computer, is one of the most powerful and popular machine in the world. Computer is being used everywhere. Here are some places where they used computers to do their work easily.

Government: In the different department of the government they used computer to

Their future planning, to manage ecosystem, control and law enforcement activities. Some other places are: Traffic, School, Tourism, Aviation, Information & Broadcasting etc.

Education: Today's Computer is playing an important role in education because without computer there is very difficult to people's who is prepared their lessons in the computer. Special lectures prepared by experts in the computer as many more time as he wants. Computers are helping teachers and students in educational sector.

Science and Technology: Without computer there is no imagining of science and technology. In one day there is thousands of scientific applications are processed in the computer.

Everyday they have to weather forecasting, which involve solution with mathematical equations using worldwide data about air pressure, temperature, humidity and other values.

Business and Industry: Computer increase or improve their working capacity and efficiency in the office. They can records their files and programs easily with safe. Information can search immediately. Cost of production goes down and profit goes up. The quality of products is improved so everyone wants that product. Very difficult work is done by robots. Working hours of labors are reduced; they get more leisure.

 
Humanities: In recent years, computer have become popular among  people having interest in music, videos,literature,social networking, history, graphics, arts and other branches of humanities.

 
Health Care:  Computers are also being used by a health care professional to planning and control purpose. Medical researchers are using computer as a tool in their search for cures of deadly diseases like a Cancer and Aids.

Communication: Computers are capable of manipulating and transmitting text at very fast rate. We can easily chat a friend by a home with one country to another country. Anybody may do office work, reservation of their bus and tickets, purchase of shares and other works stayed by a home. Text, voice, data and picture can easily transmit nowadays.

Recreation and Entertainment: Nowadays computer is also being used for a entertainment and recreation in our daily lives. For examples,

I) In sports, computer compile statistics, sell tickets, create training programs for athlete and suggest game plan strategies based on the competitor's past performance.

II) In the movie we can see a different type of a person, animals and aliens character which we have ever seen in our life. These all characters are created by a computer. Designers have a freedom to design the character of a movie so they can add effects.

III)In shopping center, almost everyone buy a products and going to pay on the counter. While they show their products they brought automatically actual price and data enters into a computer, and calculates the cost and then prints a receipt.

History of Computer

Like others, computer has its own history in its amplitude. The history of computer starts from 4000 years ago. Before 1600 century Chinese people developed a kind of machine can ABACUS, which was made of rectangular wooden frame. It had horizontal rods with beads strung; Addition and subtractions were done by changing the position of the beads. Hindu Brahmin developed the natural number 0 to 9.

 

Abacus: It is the first country and calculating device that was developed by the Chinese people the Abacus was first used for computations in 3000 B.C. It was made of a wooden frame on which there were strings. The frame was divided into two parts heaven and earth by a mid bar.

Napier's Bone: John Napier Scottish Mathematician invented this device in 1614 AD. This Device was used for multiplication and division. It consists of nine pieces of square cards; each divided vertically into nine squares. Each square again is divided diagonally from the right hand corner to the bottom left hand corner and in each card multiplication tables from 1 to 9 written. He placed ten above the diagonal of the square and unit below.

The slide Rule: William Ought Red invented the Slide Rule in 1620. This device was based on the principle of Logarithms, which was developed by John Napier in 1614.There are three main parts of slider rule.1. Body, 2. The slide with scales make on it, 3. Their transparent cursor marked with sharp lines as indicator.

Pascaline: French mathematician, Blaise Pascal developed Pascaline in 1642. Pascal's calculator was limited to performing only addition and subtraction operation. This machine was very simple, about the size of a shoebox. It consisted of a train of number wheels. It position could be observed through the window in the covered of the box that enclosed the mechanism. Multiplication could be performed by repeated addition and division by repeated subtraction.

Difference Engine and Analytical Engine: Charles Babbage in 1822 AD invented a machine called Difference Engine with mechanical memory to store results. It was based on the difference tables of squares of the numbers. After Analytical Engine was also developed by Charles Babbage in 1830s.It consisted of the input unit from taking data and instructions mill for performing calculation, memory with a suitable output device that was used in giving the final result.

Lady Augusta Ada Lovelace: One of the great supporters of Charles Babbage was Lady Augusta Ada (the daughter of famous poet, Lord Byron).She convinced Babbage to used binary concept in his Analytical Engine. She wrote different types of programs that ware used in the Babbage machines. So she is remembered as the "First Programmer" in the history of computer science and has to her credit a computer language called ADA name after her.

Dr.Herman Hollerith: He was the first person to used punched card practically on his Census Tabulation Machine in 1880s.The information is stored as holes in cards,which are interpreted by machines with electrical sensors.The cards ware punched by a machine called Punched Card Machines or Hollerith's Tabulation Machine. New companies were established under the name International Business Machine Company and he became the founder of IBM.

Mark-1 (Howard Aiken): In the late 1930s, next important event was added in the history of computer.The electromechanical computer was born with the development of MARK-1 in 1944 by Howard Aiken with the help of IBM. It also used the punched cards designed for Difference Engine.It was 51 ft. long,8 ft. high and 13 ft. wide. It was used to produce ballistics tables in 2nd world war.

Electronic Numerical Integrator and Calculator (ENIAC): It is the electronic computer that was developed by John Mouchlay and J.Priosper Eckert in 1947.It was based on the decimal number system.18, 000 vacuum tubes were use in ENIAC.

 Electronic Discrete variable Atomic Computer(EDVAC):In 1949,the first electronic computer was developed by John Mauchly and John Presper Eckert with the help of A. Burks,Goldstine and Neumann.This machines was used to store the data and information as well as the instructions.This computer operated electronically.

UNIVAC-I (Universal Accounting Computer): John Mauchly and Eckert Founded their own company in 1946 and began to work on the universal Automatic Computer (UNIVAC):general-purpose commercial computer in 1951.cit was the first commercially used electronic computer in the world.

Characteristic of computer

Speed: Computer performs complex calculation at a very high speed. This speed varies from a few microsecond to nanosecond. This is the major factor, which is mainly responsible for the development of computers,

                                             Fractions of a second

1 Millisecond       = 1/1000th of a second (10-3)

1 Microsecond     = 1/1000000th of a second (10-6)

1 Nanosecond     = 1/1000000000th of a second (10-9)

1 Pico second      = 1/1000000000000th of a second (10-12)

Accuracy: Computer do not make mistakes. Computer always given 100% actual output (result),if the user provides correct input and instructions. If any mistakes occur in any calculation they are due to manual error but not of computer. Since it is 100% accurate, it is reliable.

Storage: The computers have very large storage capacity. The stored information also can retrieve immediately. That helps to analyzing data and taking quick decisions.

                                      Computer Store data in terms of memory units

        0 or 1      = 1 Bit (Binary Digits)

      8 Bits        = 1 Kilobyte (KB)

 1024 Byte       = 1 Megabyte (MB)

 1024 KB         = 1 Gigabyte (GB)

 1024 GB         = 1 Terabyte (TB)

Versatility: Computers are an electronic device which we can used in different fields such as School, Science and Technology, Hospitals, Offices, Government, Industry etc, to perform various tasks. Ability to perform various task and computer can capable to do is called versatile. A computer can process any kind of data.

Diligence: Capability of performing repeated operation without any tiredness and any mistakes are known as Diligence. A computer is capable of performing the required task continuously with the same speed, accuracy and efficiency without any error. This characteristic of computer makes it useful for repetitive jobs like process control and quality control.

Reliability: If we can input data and instruction correctly then computer output is generally very reliable. If there is incorrect data and unreliable programs input then they gives us computers errors and wrong results since the computer is 100% accurate, it is reliable.

Memory

The memory is the computers work area of computer. This is the place where our data and programs get stored before being used processed and the place where the results get stored prior their output. There are two parts of memory.

Primary Memory:  It is the part of memory which stored data and information for present and future use. It has two sub types:

RAM: It is running work space of Computer.  Initially every task is stored in RAM, when we save information; they are stored in secondary memory (storage devices). It is also called temporary and volatile memory because the information is erased when the power is switched off. RAM is used to faster the speed of computer. Memory is measured in bytes: 64MB, 128MB, 256MB, 512MB, 1GB…… are the sizes of RAM available in the market.

 

ROM: ROM is read only memory. It contains programs and data that are permanently recorded when the computer is manufactured/. We can see the information of ROM at the time of booting the computer. We can only read the information of ROM. We can't write/edit or delete the information available on it.

Secondary Memory:  The secondary memory is the permanent memory. The information in this memory is not lost when the power supply is off. The most common secondary memory devices are hard disk, Floppy disk, zip disk, Magnetic tape and Optical disk.

 
Floppy Disk: A floppy disk is a small data storage device which is general used to transfer data from the hard disk. It is also called as Removable Disk. It is a flexible or portable type. It has 1.44 MB capacity till now. Its drive also lies inside the system board.

Hard Disk: Hard disk is the major storage device of computer. All the files and programs are stored in hard disk. It lies inside system board (CPU Box). Hard disk can store the huge amount of data and can access data faster then any other storage devices. Today's hard disks capacities are measured in gigabytes . It is made up with magnetic tape.

Optical Disk:  Optical Disk is produced using laser technology, and as a result offer much higher density and reliability then magnetic disks. Disks are made of plastic or metal with highly reflective coating usually aluminum. There are mainly three types of optical disks available in the market.

·         CD- ROM (Compact disk – Read only memory)

·         CD- RW (Re – writable memory)

·         DVD ( Digital Video/Versatile Disk)

CD ROM: CD- ROM stand for Compact Disk – Read Only Memory. The original name was WORM drive, which means write Once Read Many. They can store up to 700MB (larger CDs can store up to 20GB) and are used for distribution of massive quantities of data (e.g. encyclopedia, document archives, manuals statistics and software package) at relatively low cost.