Computer is an Electronic Device that can receive a set of instructions or program or any other information. It stores and processes the data, and produces the output. It works under the direction of a detailed stored program of instruction.

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History of Computer

Abacus is the first manual device used for adding numbers which is invented by Babylonians before 5000 years.

After that different device like Slide Rule, Arithmetic Engine, Difference Engine, Analytical Engine, Tabulating Machine, etc. were used for calculations.

ENIAC (Electronic Numeric Integrator And Calculator) is the first electronic device invented in the year of 1946.

Generations of Computer
Generation (Period) Components Used Description
First Generation
(1940 – 56)
Vacuum Tubes / Thermionic Valve Machine Input based on punched cards & paper tape. Worked on binary-coded concept.
Second Generation
(1956 – 63)
Transistors Faster than First Generation. Size is smaller than First Generation
Third Generation
(1963 – 71)
Integrated Circuits Faster, Smaller, Consumes less power and generated less heat. Easier for commercial use.
Fourth Generation
(1972 – 2010)
Microprocessor Very small in Size, Portable, Faster, Accuracy. Cost is reduced to common people.
Fifth Generation
(2010 – till date)
Artificial Intelligence, Quantum computation, Nanotechnology, Parallel processing, etc. High capability and large memory capacity. Fast and multitasking.
Contributions of Pascal, Charles Babbage, Lady Ada Lovelace and John Von Neumann
Blaise Pascal
  • He was a French Mathematician . He invented the Arithmetic Engine, which is a basis for Calculators. He used Gear Wheels and suitable dialing system to operate the gear wheels in his Calculators.
Charles Babbage
  • Charles Babbage, Father of Computer Science , invented the Difference Engine and Analytical Engine. He introduced the concept of Block Diagram which we are using now.
Lady Ada Lovelace
  • She was a Mathematician. She was the first lady who told that computers can be programmed so, she is called as the First Programmer. A programming language ADA is widely used in American defense Computers.
John Von Neumann
  • He was a Hungarian Mathematician. He introduced the concept of stored program. The instructions given to the computer are first stored in memory they are then extracted from memory and executed one by one.
Applications of Computer
Home Online Bill payment, online education, watching movies at home, home tutoring, social media access, playing games, internet access, work from home etc.
Medical Field Maintaining database of patients’ history, diagnosis, X-rays, live monitoring patients, robotic surgical devices to perform delicate operations.
Entertainment Watching movies, playing games, listening music, photo editing.
Industry Managing inventory details, designing purpose, creating virtual sample products, interior designing, video conferencing, Online Sales & Service, Online Marketing, Stock Markets etc.
Education Online classes, online examinations, referring e-books, online tutoring etc.
Government Maintaining citizen’s database, Missile Development, Recruitment, Grievance, Satellites, Rocket Launches, etc. and supporting a paperless environment.
Banking Store details of customers, employees, transactions (withdrawal, deposits, etc).
Business Maintaining transactions related to suppliers, employees and customers. Purchase and sales entries.
Training Computer based training to save time and travelling cost. Online class connects people in various locations.
Arts Dance, Photography, Arts & Culture.
Advantages of Computer

The Modern world is more dependent on Computer because of the following reasons:

  1. Saves time by quick performance.
  2. Reduces Intellectual Strain.
  3. Gives 100% accurate result.
  4. Connects everyone using internet.
  5. Stores huge amount of data easily.
  6. Increases the productivity.
Terms related to Computer
ASCII American Standard Code for Information Interchange: A standard coding system for computers..
Algorithm An algorithm is a series of steps, especially in a computer program, which will give the answer to a particular kind of problem / question.
API API stands for Application Programming Interface. APIs sit between an application and the web server, acting as an intermediary layer that processes data transfer between systems.
Big Data Big data is a quick way to refer to the massive amounts of data collected by organizations on a day-to-day basis.
BIOS Basic Input and Output System: Responsible for handling particulars of input / output operations.
Binary A selection, choice or condition involving two possibilities. The Computer functions on binary basis (0, 1)
BIT Binary digIT: It is the smallest unit of data in a computer. It stands for either 0 or 1.
Boolean A function in programming with binary choices like ‘Yes / No’ or ‘True / False’.
Boot The initial loading of` an Operating System / Programs into a computer.
Buffer A device or storage area where data are temporarily stored.
Bug It is an error. It can be a hardware malfunction or a software programming error.
Backup Alternate facilities of programs, data files, etc. used in case if the original copies are destroyed, lost, or fail to operate.
Camel Case Camel case is the practice of writing compound words without space or punctuation but each word starts with Capital letter.
Cookie A packet of information that travels between a browser and the web server.
Cloud Storage Cloud Storage is a mode of computer data storage in which digital data is stored on servers in off-site locations. The servers are maintained by a third-party provider who is responsible for hosting, managing, and securing data stored on its infrastructure.
CRT Cathode Ray Tube: An electronic tube with a TV like screen upon which information can be displayed.
Cyber Security Cyber security is the process of protecting data from unauthorized users or hackers. It also represents a huge sector of the tech industry as more and more companies race to stay ahead of cyber criminals and security threats.
Data A collection of fact in raw form that become information after proper processing.
Debug To detect, trace and eliminate errors in computer programs.
Download The transfer of information from a remote computer system to the users system.
IDE An Integrated Development Environment is a software tool where developers can write code and run their programs. Many provide useful features like syntax highlighting, debugging tools, version control and more.
IP Address The numeric address of a computer connected to the Internet.
Latency Latency is the measure of time between entering an input and the returned output.
LCD Liquid Crystal Display: It is a flat panel electronic video display that uses the light modulating properties of liquid crystals.
LED Light Emitting Diode: It is same as LCD but which uses an array of light-emitting diodes as pixels for a video display.
Program A set of actions (instructions) that machine is capable of interpreting & executing. Used to design, write & test such instructions.
Programmer A person, who designs, writes and tests computer programs.
Port That portion of a computer through which a peripheral device may communicate. It’s identified with the various plug-in jacks on the back of the computer.
Scripts In programming terms, Script is a line by line set of instructions for a computer program to follow. These are often used for automation or for generating dynamic page content.
Syntax Syntax refers to the rules that dictate the structure of a language.
Upload To transfer information from a users’ system to a remote system.
  • Computer is an Electronic device, so we can compare its speed with the Speed of Electrons. The time required to execute a basic operation (like addition, subtraction, etc.) is known as the Speed. Small computers take a few Microseconds (10-6 seconds) to execute a basic operation.
    Large Computers take only a few Nanoseconds (10-9 seconds) for the same.
  • We store data, instructions and computer programs in memory. Instructions in a program are executed one by one at a very great speed. The results are also stored in memory. The data instructions and programs stored in memory can be got back any time we want. Computers also support storing of data and instructions in secondary memories like floppy or hard disks.
  • Computer is a versatile tool. It means that we can use the computers for business, scientific or any other applications. A computer does a lot of wonderful works with its basic capabilities (like arithmetic, logical comparisons, move data). Hence, we call it a versatile tool.
  • Computers can work for long hours without getting tired. If a computer has to do 10 million calculations, it will do all of them with the same Speed and Accuracy.
  • The ability of the computers to automatically do the given work (without human help) is called automation.
  • Computers are 100% accurate. They do not make mistakes. If the result is wrong then it will be only because of the programmer or user..
  • Hardware refers to the visible and touchable (physical) parts of the computer including the Central Processing Unit (CPU), Memory, Keyboard, Monitor, Scanner, Printer, RAM, Case and Drives (Floppy, Hard disk, CD, DVD, Optical, Tape, etc.). Hardware parts can be replaced if it is damaged.
  • Software refers to the computer programs. These programs are used to run and control the hardware. Programs are also called Software. These programming instructions cause the computer to perform arithmetic and logical operations or comparisons. Software is developed using programming languages like C, C++, Java, Python etc.
    Software is categorized as System Software and Application Software.
System Software
  • System software is software that directly operates the computer hardware and provides the basic functionality to the users as well as to the other software to operate smoothly. It is like an interface between hardware and user applications.
Application Software
  • Application software is designed to perform a specific task for end-users. It is a product or a program that is designed only to fulfill end-users’ requirements. It includes word processors, spreadsheets, database management, inventory, payroll programs, etc. Ex: Word, Excel, PowerPoint, Tally, Photoshop, etc….
Relationship between Hardware and Software
  • To use a computer, we must have both hardware and software. Software is to hardware as what fuel is to a motor car. Hardware without software is powerless. Software without hardware is useless.
Input Unit
  • The purpose of the input unit is to get data and instructions from the user and transmit them into computer memory. Examples: Keyboard, Mouse, Joystick, Lightpen, Scanner, Microphone, …
Output Unit
  • The purpose of the output unit is to get the output results from the memory, and give it to the user in human readable form. Examples: Monitor, Printers, Plotters, VDU (Visual Display Unit), Speaker …
Central Processing Unit
  • The CPU is the heart of a computer. It consists of Memory unit, Arithmetic & Logic Unit and Control Unit.
Memory Unit
  • This unit stores the data and instructions. The intermediate and final results of a program are also stored in memory. A program can be executed (run) only when it is brought to main memory.
Arithmetic Logic Unit (ALU)
  • It does all arithmetic (addition, subtraction, multiplication, division) and logical operations (comparison of data). It also stores the results of intermediate calculations.
Control Unit (CU)
It is the Supervisor of all the other units. The main functions are
  • Give commands to transfer data from the input device to the memory and from memory to the ALU.
  • Transfer the results from memory to the output device.
  • Store the program in memory. Take instructions one by one from memory, understand and give commands to other units.
Classification of computers based on the basis of working
Analog Computers
  • A computer that operates by measuring continuously varying quantities like voltage and current is called Analog Computer. Examples: Thermometer, Slide rule, Dial gauge, Speedometer.
Digital Computers
  • A computer that operates by counting is called a Digital Computer. Examples: Digital Watches, Personal Computers.
Hybrid Computers
  • They are a combination of both Analog and Digital Computers. It has the Speed of Analog Computer and the Memory & Accuracy of Digital Computer. Examples: Computers used for Process Controls.
  • 1. Computers used for control of space vehicles.
  • 2. Fighter aircrafts.
  • 3. Intensive Care Unit.
Difference between Analog and Digital Computers
S.No. Analog Computers Digital Computers
1. Operates by measuring continuously varying quantities like voltage and current. Operates by Counting.
2. Less accuracy. More accuracy.
3. Limited Applications. Vast Applications.
4. Limited memory. Vast Memory.
5. Gives results in graphical form. Gives results in discrete form.
6. Cannot process alpha-numeric information Can process alpha-numeric information
Classification of computers based on the basis of Size
Micro Computer (PC – Personal Computer)
  • It is a single user computer system having moderately powerful, small, inexpensive microprocessor designed for an individual user. Businesses use personal computers for word processing, accounting, and desktop publishing and for running spreadsheet and database management applications. At home, the most popular use for personal computers is playing games and surfing internet.
  • It is also a single user computer system which is similar to personal computer but have more powerful microprocessor. This is used for engineering applications (CAD / CAM), Desktop Publishing, Software Development and other such types of applications which require a moderate amount computing power and relatively high quality graphics capabilities.
Mini Computer
  • Minicomputer is a multiuser computer system which is capable of supporting upto 250 users simultaneously. Minicomputer is a term that is no longer used much. In recent years, minicomputers are often referred to as small or midsize servers (a server is a central computer that provides information to other computers).
Mainframe Computer
  • Mainframe is very large in size and is an expensive computer capable of supporting hundreds or even thousands of users simultaneously. Mainframe executes many programs concurrently and supports many simultaneous execution of program. Mainframe computers are primarily used in :
  • 1. Research
  • 2. Health Care
  • 3. Libraries
  • 4. Institutions
  • 5. Large Businesses
  • 6. Insurance Agencies
Super Computer
  • Super Computer is an extremely fast computer which can execute hundreds of millions of instructions per second. This is one of the fastest computers currently available. Super Computers are very expensive and are employed for specialized applications that require immense amount of mathematical calculations. Example: Weather Forecasting, Scientific Research, Electronic Design and analysis of Geological data.
Desktop Computer
  • A desktop computer is same as a personal computer but the computer is located on a desk / table due to its size and power requirements. This is used for Desktop Publishing works, Official and Commercial works, etc.
Laptop Computer
  • Laptop computers have an L-shape design and the screen can be lowered and closed to allow easy transportation of the machine. The primary feature that attracts users to laptops over desktops is their portability. Laptop computers provide users the ability to run the machine using an internal battery or an outside power adaptor. It is most used at work, education, games, browsing, business, personal and for home.
Palmtop Computer
  • A computer which is small enough to hold in one hand and operate with other is called as “handtop” or “palmtop” which has small keyboards or specialized keypads tailored to specific industries. Example: Tablet.
Classification of computers based on the basis of Processor
Personal Computer (PC)
  • PC means Personal Computers. The I/O devices connected to a PC are normally a keyboard, Visual Display Unit, Mouse and a Printer. PCs are used in banks, offices, homes, business and other organizations.
different processors comparison based on mode, software, slot width, hardware, dma channels RAM, Floopy controller, standsard drive, keyboard interface, CMOS memory clock
  • PC-XT means Personal Computer – Extended Technology
  • The Processor is 8088.
  • Floopy Disk Drive - 1 No.
  • RAM Size is 640 KB.
  • Hard Disk Drive - 1 No.
PC-XTs are used in banks, offices, homes, business and other organizations.
PC-XT means Personal Computer – Advanced Technology
  • 1. The Processors are: 80286, 80386, 80486, Pentium-I, Pentium-II, Pentium-III, Pentium-IV, Dual Core, Core2Duo, i3, i5, i7, etc.
  • RAM size varies from 16 MB to 8GB depending upon the processor.
  • 3. It supports both Floppy and Hard Disk Drive.
  • 4. Speed is higher than that of PC-XT.
Most of the computers used in homes, banks, offices, industries, business and other organizations today are PC-ATs only.
  • Bit means Binary digIT. It is either the digit 0 (OFF state) or the digit 1 (ON state). Data and instructions are stored in memory as a combination of 0’s and 1’s.
  • A byte is a group of 8 bits.
    1) 1000 1001 is a byte.
    2) 0011 0011 is a byte.
  • A word is a group of bytes. Small computers use a word length of 8, 16, 32 or 48 bits. High speed computers use a word length of 64 bits or more.
1 Character = 2 bit
4 bits = Nipple
8 bits = 1 byte
1024 bytes = 1 Kilobyte (KB)
1024 Kilobytes = 1 Megabyte (MB)
1024 Megabytes = 1 Gigabyte (GB)
1024 Gigabytes = 1 Terabyte (TB)
1024 Terabytes = 1 Petabyte (PB)
1024 Petabytes = 1 Exabyte (EB)
1024 Exabytes = 1 Zettabyte (ZB)
1024 Zettabytes = 1 Yottabyte (YB)
  • Memory is best storage part to the computer users to save information, programs etc. Memory is categorized into two types, Main Memory and Secondary Memory.
primary memory, cache memory, secondary memory, RAM, ROM, Floppy, CD-ROM, Hard Disk, Solid State Drive
  • The main memory unit of a computer is called primary memory or main memory. Data, instructions and programs are stored in this memory in binary form. Information stored in this is directly processed by the computer at great speed. It is a volatile memory because it can’t store the data permanently. The memory capacity is limited.
  • The primary memory of a computer is limited and also Volatile. So, we need secondary memories like floppy disk or hard disk. We can store large amount of information in secondary memory. Information stored in this memory is permanent. They can be got back any time.
RAM (Random Access Memory
  • RAM means Random Access Memory. It is also known as Read and Write Memory. Information stored in this memory can be erased and rewritten. It is a volatile memory i.e., Information stored in this memory is lost when the power goes off. RAM also categorized into SDRAM, DRAM, . . .
Static RAM (SRAM)
  • Static RAM is a type of random access memory that retains data bits in its memory as long as power is being supplied.
Dynamic RAM (DRAM)
  • Double data rate synchronous dynamic random-access memory (DDR) is a class of memory integrated circuits used in computers. DDR SDRAM, also called DDR1 SDRAM, has been superseded by DDR2 SDRAM, DDR3 SDRAM and DDR4 SDRAM.
  • ROM means Read Only Memory. It is a non-volatile memory i.e., Information stored in the memory is not lost when the power goes off. Writing into ROM is done only once (at the time of manufacturing). We cannot write information in this memory.
  • PROM means Programmable Read Only Memory. ROM is programmed by the manufacturer. But, PROM can be programmed by any user using “PROM Programmer” device. After PROM is programmed, we can only read information.
  • EPROM means Erasable Programmable Read Only Memory. Unlike ROM and PROM information stored in this memory can be erased and rewritten. Erasing is done by exposing to ultra violet light for about 20 minutes. After EPROM is programmed, we can only read information.
  • EEPROM means Electrically Erasable Programmable Read Only Memory. Information stored in this memory can be erased electrically and rewritten. After EEPROM is programmed, we can only read information.
  • Cache memory is a chip-based computer component that makes retrieving data from the computer's memory. It acts as a temporary storage area that the computer's processor can retrieve data easily. This temporary storage area, known as a cache, is readily available to the processor than the computer's main memory source, typically some form of DRAM.
    Cache memory is sometimes called CPU (central processing unit) memory because it is typically integrated directly into the CPU chip or placed on a separate chip that has a separate bus interconnect with the CPU.
  • Flash memory is a non-volatile memory chip used for storage and for transferring data between a personal computer (PC) and digital devices. It has the ability to be electronically reprogrammed and erased. It is often found in USB flash drives, MP3 players, digital cameras and solid-state drives.
  • A hard disk is a fixed disk completely sealed in an air-tight, dust free container. A hard disk consists of a number of disks packed together and mounted on a common shaft. Disks are coated on both sides with magnetic material. A disk pack having 6 plates will have 10 recording surfaces. (The top surface of the top disk and bottom surface of the bottom disk are not used. There are movable read / write heads for each surface).
Reading / Writing Operation
  • The common shaft is rotated at the speed of 4,000 to 15,000 revolutions (or more) per minute. The read/write heads are positioned over a particular track on all surfaces. A set of corresponding tracks in all the sides form a cylinder. When an information is stored, the cylinder number, the surface number are noted. Typical hard disk storage capacities are 40 GB, 80 GB, 160 GB, 250 GB, 500 GB, 1 TB.
  • SSD Stands for Solid State Drive. An SSD is a type of mass storage device similar to a hard disk drive (HDD). It supports to read, write data and maintain stored data in a permanent state even without power. Internal SSDs connect to a computer like a hard drive, using standard IDE or SATA connections. Flash Controller and NAND Flash Memory are the two main components of SSD.
  •   CD-ROM means Compact Disk Read Only Memory. The disk is compact so that we can store as much of information as can be stored in 450 Micro floppies. The storage capacity of a CD-ROM is 700 MB. The thickness of the disk is 1.2 mm and diameter is 120 mm. Today, games and software programs are supplied in CDs only. We can also use CDs for audio-recording.

      The disk is made up of a resin such as polycarbonate. It is coated with a material like aluminum.
      Information is written into a CD-ROM by using a high power laser beam. The laser beam is used to burn tiny holes called bits on a spinning disk. The tiny pit represents “1 “and the surface without a pit “0” is known as land.
      Information is read from a CD-ROM using a low power laser beam. The reflected light from pits and lands (which will be different) is sensed by a “photo diode” for converting into electrical signals.
DVD (Digital Video Disk)
  • DVD is a type of compact disc that can store large amounts of data, especially high-resolution audio visual material. Its storage capacity is 4.7GB. This is available in three different types.
    • BD-ROM: Read only format of Blu-ray.
    • BD-R : Recordable format of Blu-ray.
    • BD-RE : Rewritable format of Blu-ray.
  • Single Blu-Ray disc is able to store data upto 25 GB whereas dual-layer Blu-ray disks can store data upto 50GB. Recording capability of a DVD or CD on a Blu-ray disc is dependent on the manufacturers’ choice. A DVD player cannot read a Blu-ray disc, since it uses red laser to read the information from the disc, rather than a blue laser.
Blu-Ray DVD
  • Blu-ray disc is a digital optical disc data storage format. Blu-ray discs have an advantage over DVDs of storing high definition video resolution. The Blu-ray discs are named so because of their underlying technology, which uses a blue-violet laser to read and write data. Blu-ray discs have a wide range of formats which include the following
    • DVD-ROM (Read-Only)
    • DVD-R (Writable)
    • DVD-RW (Rewritable or Erasable)
  • A pen drive or a USB flash drive is a portable data-storage device which replaced the floppy drives. And now it is the most popular data-storage devices among consumers. This can be easily carried from place to place by students, professionals, etc. Its storage capacities vary from 2GB to 32GB and using this we can store large documents, photos, music files and video clips.
  • Zip drive is a medium-capacity floppy disk drive developed by Lomega Corporation. At first zip disks had capacities of MB, but later versions were increased to first 250MB and then to 750MB. This portable disk drive is primarily used for backing up and archiving personal computer files.
  • An external hard disk is just a hard disk drive (HDD) or solid-state drive (SSD) that needs to be connected to the computer rather than being inside the computer. External hard disks are sometimes referred to as portable hard drives or mobile hard drives. External hard drives have different storage capacities, but they can be connected to the computer via USB, FireWire, or wirelessly.
Components of CPU
  • Of all the devices, CPU is an important device that is responsible for the computer to perform various tasks. It is to be mentioned that CPU is not a single device rather the following components, when assembled perfectly, build up CPU:
    • Motherboard
    • Processor
    • Hard disk
    • SMPS
    • RAM
    • Connecting Wire
    • ROM
    • Graphics Card
  • A motherboard is the multiple layer printed circuit board inside a computer that connects the different parts of a computer together. It has sockets for the CPU, RAM and expansion cards (graphics cards, sound cards, network cards, storage cards etc)... and it also hooks up to hard drives, disc drives and front panel ports with cables and wires. Motherboard is also known as a mainboard, system board, PCBs, mobo or MB.
SMPS (Switch Mode Power Supply)
  • SMPS is a power supply that uses a switching regulator to control and stabilize the output voltage by switching the load current on and off. These power supplies offer a greater power conversion and reduce the overall power loss. SMPS is used to transfer power from a DC/AC source to a DC load. Most switched-mode power supplies convert a higher voltage (110V or 220V AC) to a much lower DC voltage like 24V, 12V, or 5V
Connecting Wire attached with SMPS
20 + 4 Pin ATX / Motherboard Connector This is the main ATX connector that supplies power to motherboard and other components like RAM, graphics card, PCI cards that are connected to motherboard.
CPU 4 + 4 Pin Connector This is the 12 Volt connector that supplies power to processor. Some motherboards have 4 pins 12V CPU socket and some have 8 pins 12V socket, therefore most of the good power supplies come with 8-pin (4 + 4) detachable connectors which can be split into two 4 pin connectors.
SATA Power Connector This power connector is used to power up SATA devices that mostly include Hard Disks, DVD Writers / Drives.
Peripheral 4 Pin Molex Connector Peripheral 4 Pin Molex Connector is used to provide power to IDE devices and other peripherals like Fans, case lights etc.
PCI-e 6 Pin / PCI-e 8 Pin Connector PCI-e 6 Pin or PCI-e 6+2 Pin are 12 Volt Connectors that are used to provide power to mid to high range graphics cards that require extra amount of power for their working.
  • A sound card is an expansion card or IC for producing sound on a computer that can be heard through speakers or headphones. Although the computer does not need a sound device to function, they are included on every machine in one form or another. This is either in an expansion slot (sound card) or on the motherboard (on board).
  • Graphics cards, also called graphics accelerators or Video Cards, is a type of display adapter installed within most computing devices to display graphical data with high clarity, color, definition and overall appearance. Programs such as photo editors and Web browsers may benefit from 2D acceleration, while CAD design programs and video games will most likely benefit from the card's 3D acceleration. Some programs rely so heavily on the video card, that they will not run if a supported video card is not installed.
  • A computer uses a Network Interface Card (NIC) to become part of a network. The NIC contains the electronic circuitry required to communicate using a wired connection (e.g., Ethernet) or a wireless connection (e.g. WiFi). A Network Interface Card is also known as a Network Interface Controller, Network Adapter, or Local Area Network (LAN) adapter.
MODEM (MOdulator-DEModulator)
  • Modem is an electronic device that makes possible the transmission of data to or from a computer via telephone or other communication lines. There are three kinds of modems - Cable, DSL, and Fiber. Modem operates via different cable mediums depending on Internet Service Provider (ISP).
  • Input Devices are used to get data, instruction and programs from the user and store them in computer memory in binary form.
  • It is an input device. It gets data, instruction from the user and stores them in computer memory. When a key is pressed, it generates an ASCII code (American Standard Code for Information Interchange). This code is transmitted into the computer. It looks like a typewriter. It has Alphabet Keys, Numeric Keys, Special Character Keys, Function Keys, Navigation keys and Control Keys.
    It usually has 105 or 108 keys. Using keyboard, the data and instructions can be entered quickly into the computer.
    QWERTY keyboards the standard keyboards has designed as the six alphabets Q, W, E, R, T and Y are in the first row.
    Keyboards are connected to the computer with Wire or Wireless . Bluetooth or Infrared (IR) technology is used for wireless connectivity.
    A Virtual Keyboard is software that is used to emulate a standard keyboard. A picture of a keyboard is displayed on a computer screen and the user points and clicks on the pictures of keys to enter text. Smartphone is the best example for Virtual keyboard.
  • It is an input device, also called as pointing device. The pointer can provide data or instructions to the computer for processing. It has two buttons (left and right) and a scroll wheel between these two buttons. When it is moved across a flat surface, the cursor on the VDU also moves. It is easier for non-typists. Mouse is very important for Windows and other GUI (Graphical User Interface) applications.
    Nowadays optical mouse is used.
  • A graphics tablet (also known as a digitizer, digital graphic tablet, pen tablet, drawing tablet, external drawing pad or digital art board) is a computer input device that enables a user to hand-draw images, animations and graphics, with a special pen-like stylus, similar to the way a person draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures. It can also be used to trace an image from a piece of paper that is taped or otherwise secured to the tablet surface.
  • Scanners allow us to transfer pictures and photographs to our computer. A scanner ‘scans’ the image from the top to the bottom, one line at a time, and transfers it to the computer as a series of bits or a bitmap.
  • A digital camera records and it stores photos in digital form. The images are stored on a memory chop or disk that can be transferred to our computer. Many current models are also able to capture sound or video, in addition to still images.
  • Joystick is an Input device which is used as a navigation control while playing games.
  • Pen drive is a portable storage device which is available at various sizes.
  • Output Devices are used to get the output from the computer memory and give them to the user in human readable form. The output data are either in the form of a soft copy or hard copy. The printed content is Hard Copy. The output shown in the display is Soft Copy.
  • Monitor is an output device which provides visual display of data. This helps to correct wrong entries. It also shows the results of programs. In olden times we used monitors with Cathode Ray Tube (CRT). But now we are using LCD (Liquid Crystal Display) and LED (Light Emitting Diode) Though, CRT monitors were used initially around 1950s, power consumption by CRT monitors was relatively higher, than by the monitors that we are using today.
  • Considering this, various developments were made on monitors, which led to the birth of LCD & LED monitors, both of which consume less power than CRT monitors & LED being the least consuming. The resolution of the monitor determines the quality of the display. Some resolutions are 640 X 480 pixels, 800 X 600 pixels and 1024 X 768 pixels.
  • Printer is an output device which is mainly used to print text or images on the paper. The data stored in the memory is softcopy whereas the output taken on the paper is hardcopy.
  • Printers are categorized as Impact and Non-impact printers.
  • Impact printers generally utilize hammers, pins, or wheels to hit against an inked ribbon to print on paper. Non-impact printers use a spray of ink, laser, or heat and pressure to execute their printing operation. Different types of printers are Dot Matrix Printer, Laser Printer, Inkjet Printer….
  • It prints characters as a 7 X 5 matrix. That is, each character is printed in 7 rows and 5 columns. For example, “L” is printed as the picture. The dots are produced by wires fixed to a print-head. The wires are operated by a solenoid [a coil producing magnetic field when current is passed through] operated by signals from CPU. When operated, they protrude [come out of the head], strike the ribbon against the paper producing dots and go back in to the head.
  • 1. Cost is Low.
  • 2. Easy to Operate.
  • 3. Prints 30 to 300 characters per second.
  • They are high speed non-impact printers. The printing speed is from 10 to 20 pages per minute. Because of the quality and speed, today we use them in place of the offset printing machines. A dry toner is applied on the drum surface. The toner sticks to the charged areas of the drum. The image of the drum is then transferred to the paper by heat and pressure.
  • 1. Printing Quality is High.
  • 2. Printing Speed is High.
  • 3. A replacement for offset machine.
  • Characters and images are formed from dots. The dots are produced by tiny droplets of ink on the paper. Actually, this printer contains an ink tank from which ink can be pumped through a nibble. The droplets are then guided to proper position on the paper by electrically charged deflection plates. The printing quality is good because a character is formed by dozens of ink dots. If a droplet is not needed for a particular character, it is recycled back to the ink tank.
  • 1. Cost is low when compared to laser printers.
  • 2. Printing Quality is High.
  • 3. Less Noise.
  • A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated pens. Unlike a regular printer, a plotter can draw continuous point-to-point lines directly from vector graphic files or commands.
Types of Plotters
  • Drum Plotters, which draw on paper wrapped around a drum that turns to produce one direction of the plot while the pens move to provide the other direction.
  • Flatbed Plotters, which draw on paper placed on a flat surface.
  • Electrostatic Plotters, which draw on negatively charged paper with positively charged toner.
  • Inkjet Plotters, which use inkjet printer technology and colored inkjet pens to deliver beads of ink in an assortment of colors to the drawing surface using vector graphic technology to move the pen plotters.
  • A speaker is an output device through which we can hear sound. It is an external device which is connected to the computer using port.
  • It is also an output device like speaker but only one person can hear the output at a time by wearing it on the ears.
  • It is an output device using which the output is projected onto a flat screen. A projector is often used in meetings or to make presentations. It allows the display to be visible to many people.
  • The functioning of a computer system is based on the combined usage of both input and output devices.
  • Touch Screen
  • Headset
  • Audio Cards / Sound Cards
  • Modems
  • Network Cards
  • A port is a physical docking point using which an external device can be connected to the computer. External devices are connected to a computer using cables and ports. Ports are slots on the motherboard into which a cable of external device is plugged in. Examples of external devices attached via ports are mouse, keyboard, monitor, microphone, speakers, etc.
Types of Ports
  • There are various types of ports like Serial Port, Parallel Port, PS/2 Port, Universal Serial Bus Port (USB Port), VGA Port, etc. Ports are shown in the figure.
Parallel Port
  • A parallel port is an interface allowing a personal computer to transmit or receive data down multiple bundled cables to a peripheral device such as a printer. A parallel port has multiple connectors and in theory allows data to be sent simultaneously down several cables at once
USB (Universal Serial Bus) Port
  • USB can be used to connect keyboards, game controllers, printers, scanners, digital cameras, removable media drives, etc. With the help USB hubs it can be connected upto 127 peripherals to a single USB port. USB is also faster than older ports, such as serial and parallel ports. Most of the peripherals like printers, scanners, digital cameras are made with USB ports.
Installation of Scanner and Printer
  • Connect your printer by a wire and plug it into the device. It will connect automatically, the PC will download the right drivers for the device, and you can use it right away.
  • To connect a wireless printer, follow these steps:
    • Click the Start button, and then select Settings → Devices → Printers & scanners → Add a printer or scanner.
    • Wait for it to find nearby Printers, then choose the one you want to use, and select Add device. If you want to remove the printer later, just click on it and select Remove.

    Connecting Monitor, Mouse, Keyboard to System Unit
    • To connect a monitor, mouse and keyboard perform the following steps:
    • Locate the graphics adapter at the rear of the system.
    • Connect a keyboard and mouse to the USB ports.
    • Connect a standard monitor to the port in the system.
    • Connect the power cables to the system.
    • Power on the System.
Fill in the Blanks
  1. Arithmetic Engine was invented by Blaise Pascal.
  2. Charles Babbage is called as Father of Computer.
  3. The world first programmer is Lady Ada Love Lace.
  4. Expansion of ASCII is American Standard Code for Information Interchange.
  5. Components used in Second Generation were Transistor.
  6. A byte consists of 8 (eight) bits.
  7. Expansion of RAM is Random Access Memory.
  8. OCR stands for Optical Character Reader.
  9. VDU means Visual Display Unit.
  10. Pentium i5 refers Processor of a Computer.
  11. EEPROM means Electrically Erasable Programmable Read Only Memory.
  12. SMPS is the abbreviation of Switch Mode Power Supply.
  13. Modem is a device used for Internet Connection.
  14. Graphics Card is a device used to enhance the clarity of the display.
  15. Sound Card is a device, which connects the audio components for multimedia applications.
True or False
  1. LED is the abbreviation of Liquid Emitting Display.    (F)
  2. Digital Camera is an Output Unit.    (F)
  3. Primary memory is a volatile memory.    (T)
  4. Word in the computer consists of 13 bits.    (F)
  5. It is possible that computers can do mistake by its own.    (F)
  6. The plotter is used in the CAD applications.    (T)
  7. Von Newman designed the architecture of today’s computer.    (F)
  8. Today, we are using super computers in homes.    (F)
  9. Peripheral devices are not part of Central Processing Unit.    (T)
  10. In computers, SMPS converts AC to DC.    (T)
Write answer in two or three lines
  1. Write the components used in the various generations of the computer.
  2. Define Speed.
  3. What are the differences between analog and digital computer?
  4. What are the various units of measurements of memory?
  5. Write any two advantages of Pen drive over CD.
  6. What is Primary Memory?
  7. Write the advantages of Hard Disk.
  8. What are the types of printers?
  9. What are the types of ports?
  10. What are the components of CPU?
  11. Give examples for Storage Devices.
  12. What are the types of Networks?
  13. What are the advantages of computer?
Write answer in brief
  1. What are the characteristics of the computer? Explain.
  2. Explain and draw the block diagram of a digital computer.
  3. Explain the various memory types.
  4. Differentiate Primary and Secondary Memory.
  5. Write about Input and Output Devices.
  6. Explain about the types of Computer Networks.
  7. Differentiate PC-XT and PC-AT.