1. Chapter 2

2.  The hardware and software is used as unit to process data is called computer system.  Hardware Input Devices CPU Output Devices Storage  Software A set of instructions given to computer to solve a problem is called software. Software is also called program Computer works according to the instructions written in software

3.  Input devices  The data or instruction given to the computer is called input.  A hardware component used to enter data and instruction into computer is called input device  Output Devices  The data processed into useful information is called output.  A hardware component used to display information to the user is called output devices.

4.  System Unit  System unit is a box that contains different electronics components of a computer system.  The electronics components in the system unit are connected to the motherboard.  Important components of system unit are CPU and memory  Storage  The hardware components used to store data, instruction and information permanently are called storage devices.  Examples: Hard Disk, floppy Disk, CD, DVD, etc

5.  The data or instruction given to the computer is called input.  A hardware component used to enter data and instruction into computer is called input device  Types of input Devices  Keyboard  Mouse  Trackball  Touchpad/Track pad  Pointing Stick  Graphic Tablet  Touch Screen  Digital Scanner  Digital Camera  Joystick

17.  Hardware components that are used to receive information from the computer are called output devices.  Output devices take information from the computer and convert it in a form that is understandable by users.  Printers  Plotter  Display devices  Speaker& Headsets  Data Projectors

18.  Printer is an output device that prints characters, symbols and graphics on paper.  Printed output is called hardcopy.  There are two types of printers.  Impact Printers Dot Matrix Printers Daisy wheel printers Line Printers  Non-Printers Laser Printer Inkjet Printer

19.  Impact printer works like a typewriter.  Prints characters or images by striking print hammer or set of pins against an inked ribbon.  Ink is pressed from ribbon on the paper to produce the output.  Impact printers are used where low-cost printing is required.

20.  Produces printed images when tiny pins on a print head strike an inked ribbon.  When ribbon presses against the paper it creates dot that form characters and graphics.  Contains 9 to 24 pins.  Higher number of pins creates more dots that produce high quality image.  Speed of most dot-matrix printer ranges from 350 to 1100 characters per second.

22.  It uses a print wheel. Print wheel is called daisy wheel.  Each petal of daisy wheel contains characters  A motor rotates the wheel.  A hammer strikes a petal against the ribbon when the desired character reaches the position on the paper.  This prints the character on the paper.  Slower than dot matrix printer but better in quality

24.  Line printer is a fast impact printer.  It can print multiple characters on the same line at a time.  Its speed is measured in line per minute.  Speed range of line printer is from 300LPM to 2400LPM  Faster than dot matrix and daisy wheel.  More noisy and provide limited font capability.  Example:Band printer and chain printer

26.  A non impact printer prints characters and graphics on paper without striking paper.  The characters are printed on paper with some mean such as laser  Some printers use spray in while other use heat and pressure to create images.  These printers are faster than impact printer.  More costly than impact printers.  Produce no noise during printing  Print quality is better than impact printers

27.  Light Amplification by stimulated emission of radiation.  Similar to a photocopying machine.  Uses laser beams to burn special powder on page to create a permanent image.  Prints a complete page at a time  Typical laser printer provides a resolution 0f 1200 DPI or more.  Produces very high quality prints.  Printing speed of laser printer ranges from 12 to 45 ppm

29.  It prints characters and graphics by spraying tiny drops of liquid ink on paper.  These printers can produce quality text and graphics in both black and white and color.  Typical inkjet printer provides resolution of 600DPI or more.  Slower than laser printer.  Printers can print from 10 to 35 ppm.  Inexpensive than laser printer

31.  Plotter is an output devices that is used to produce image quality graphics in variety of colors.  Plotters are used to create maps, architectural drawings, graphs and charts.  A plotter works by drawing lines on paper using pens held in a mechanical arm.

33.  Monitor is most common output device.  The output displayed by monitor is called soft copy.  Looks like a television and displays text and graphics.  Different display screen can be distinguished on the following features.  Size  Color  Resolution  Refresh rate  Dot Pitch  Display Adapter

34.  Cathode Ray Tube  It can display text and graphics  It used CRT that creates an image by an electronic beam.  CRT consists of one or more guns that fire a beam of electrons inside the screen.  The screen is coated with very tiny phosphor dots from inside.  The beam of electrons repeatedly falls on the surface of screen.  CRT in color monitor consists of three guns RGB

36.  Laptop PCs use flat panel monitors  These monitor take less space.  Flat panel monitor use a variety of technologies  Common technology is Liquid Crystal display  LCD monitor use much less power than CRT.  These are available in different sizes such as 15, 17, 19, 21, 32 and so on.

38.  A type of output produced in the form of sound, voice or music is known as audio output.  Speakers and headsets are two commonly used audio outputs.  Many personal computers have internal speaker.  Headsets are also used to produce audio output

39.  CPU is the brain of Computer  It is the most important component of a computer  It is also called processor  A computer cannot work without CPU  CPU is located of Mother Board  Performs operations on data according to the given instructions  It can performs arithmetic and logical operations  It executes and controls the computer hardware

40.  ALU(Arithmetic and Logic unit)  Performs basic arithmetic functions such as addition subtraction multiplication and division  Logic unit perform logical operations like comparing two data items to find which is greater  CU(Control Unit)  It generates signal to direct the entire computer system  It controls and coordinates all activities of computer system.  It does not executes program instructions  Control unit communicates with arithmetic and logical unit and other parts

41.  A small high speed memory inside CPU  CPU contains number of registers  Registers are used to store information being processed.  Temporary storage area of instruction or data  Temporary results during processing are also stored in registers  Each registers has a predefined function

42.  Data in digital computers is represented as a collection of bits.  The smallest unit of data that can be used by computer is called bit.  A set of 8bit is called byte.  One byte is required to store one character.

43.  Different types of memories are random access memory and read-only memory  RAM(Random Access Memory)  It is also called Main Memory or Direct Access Memory  Each individual byte in the entire memory is directly accessible.  Program must be loaded into RAM before execution  RAM is Volatile  ROM(Read Only Memory)  Instructions in ROM prepare the computer for use.  Contents of ROM can only be read but cannot be changed or deleted.  It stores data and instructions permanently  ROM is NON-Volatile

44.  DRAM  Dynamic Random Access Memory  It is a type of memory that is used in most computers  Least Expensive kind of memory.  It requires an electric current to maintain its electrical state.  Electrical charge of DRAM decreases with time that may result in loss of data.  DRAM is recharged or refreshed again and again to maintain data.  Processor cannot access data of DRAM when its being refreshed.

45.  Static Random Access Memory  It can store its value without any need to refresh the data.  Expensive type of memory  CPU does not wait to access data so it is faster.  It utilizes more power than DRAM  It is normally used to built faster cache memory.

46.  PROM  Programmable Read-only Memory  This form of ROM is initially blank  Manufacturer can write data on it using special device  The user can write data and instruction only once  If there is an error chip becomes unusable  EPROM  Erasable Programmable Read Only Memory  Program and data written on it can be erased using ultraviolet rays.  EEPROM  Electronically erasable Programmable ROM  User can erase and write instruction using electrical devices  Contents can be modified easily

47.  Cache Memory  Designed to speed up the transfer of data and instructions.  It is located inside or close CPU.  Faster than RAM.  Data and instruction that are most recently or frequently used by CPU  Data and instructions are retrieved from RAM when CPU uses them for first time.

48.  Storage devices are used to store data and programs permanently.  Used to store large volume of data and program.  Also called secondary or auxiliary storage devices.  Important functions of storage devices are reading and writing.

49.  Magnetic Tape  Magnetic Disk  Floppy Disk  Hard Disk  Zip Disk  Removable Devices  Optical Devices CD DVD  Solid State Devices USB Flash Drive Flash Memory

50.  Flexible plastic tape coated with magnetic material  Used when large amount of data to be processed sequentially  Very cheap and economical storage medium  Major disadvantage is slow and it is only sequential

51. 1. Thin circular metal plate/platter coated with magnetic material 2. Information can be recorded on or read from magnetic surface 3. Disk must be formatted before it can be used 4. This process prepares the disk to store data. 5. Formatting process creates tracks and sectors on disk 6. Each track is divided into sectors 7. Each sector holds a specific number of characters 8. Smallest physical storage unit on disk(512Bytes) 9. Every part of hard disk is directly accessible

52.  1-Floppy Disk or diskette  Thin plastic disk coated with magnetic material  Disk is enclosed in a plastic jacket  Stores small amount of data  Data access speed of floppy disk is slower than hard disk. Inexpensive storage media  Standard size of floppy is 3.5 inch and its capacity is 1.44MB  A piece of metal covers the reading and writing area called shutter  When disk is inserted the shutters opens to read the stored data  Read/write head is used to read and write data

53.  2-Hard Disk  It is called fixed disk because it is fixed in system.  Consists of circular disk called platters sealed inside a container  Containers contains a motor to rotate the disk  Also contains an access arm and read/write head to read and write data  Platter is coated with magnetic material and is used to store data  Provides large storage capacity faster and safer than floppy

54.  1.Zip Disk  Portable disk  More storage capacity than floppy disk  Storage capacity is up to 1000MB  Zip disk can be read/write using zip drive  It is used for backing up of large data

55.  Optical disk uses laser technology to read and write data  Laser stands for light amplification through stimulated emission of radiation.  Laser beam writes on the surface by creating small holes(PIT) in the disk  Optical drives read data by focusing laser beam on the surface of the disk

56.  CD ROM  Stands for compact disk read only memory  Data cant be deleted or changed.  It is portable storage & transfer data easily.  It can store upto 700MB of data.  Information can be stored in CD Rom for many Years.

57.  Stands for compact disk recordable.  User can write data once on CD-R and read many times.  Written data can not be deleted or changed.  CD-R are known as CD burners.  Writing information on cd is called CD burning.  CD-R is also Called WORM( Write once Read Many)

58.  Stands for compact disk rewriteable.  User can write data on CR-RW many times by erasing the existing.  CD-RW normally used for applications using large volume with little update activity.

59.  Stands for digital video disk.  Similar to CD Rom.  It uses laser beam with short wave length.  Data storage capacity is increased.  Storage capacity of DVD is much greater than CD Rom.  It can store up 17GB of data.

60.  USB FLASH DRIVE  Also known as pen or keychain drive.  Provide greater capacity than floppy or zip disk.  Its capacity can be GB  Small and light weight storage device.  It is durable and can be carried on a key ring.  It can be plugged into any USB port.

61.  Flash memory cards is used in PDA, Digital Camera, Cell Phones and notebook computers.  These cards are not interchangeable.

62.  A set of instruction given to computer to solve a problem is called software.  Also known as program.  Computer software specify a sequence of operations to be performed by computer.  A computer works according to the instructions written in software.

63.  The main types of software are system software and application software.  System software  Application software

64.  System software is a set of programs to control and manage the actual operations of a computer hardware.  It controls the usage and allocation of different hardware components.  It enables application programs to execute properly  Examples of system software  Operating system  Utility programs  Device drivers

65.  Application software  A program needed to perform various applications on the computer by user  It helps a computer user to solve specific problems  Application software uses operating system in order to function  Application software runs on the top of the operating system software.  Example Word Processor Spread sheet Graphics Database