The ComputerThe Computer

an electronic data processor

Computer SystemsComputer Systemsmany systems have this structure

INPUTINPUT

BACKINGBACKINGSTORESTORE

PROCESSPROCESS OUTPUTOUTPUT

Computer HardwareComputer Hardware

– hardware is anything tangible :

Central Processing Unit – this is inside the main box

Peripherals– these are devices attached to the CPU

Peripheral DevicesPeripheral Devices

input devices– allow data to be entered into the computer

backing storage devices– allow data to be stored for processing

output devices– allow data to be output from the computer

INPUT DEVICESINPUT DEVICESKeyboardMouseJoystickTrackerballLight PenGraphics TabletBar Code ReaderMark Sense ReaderOptical ScannerMagnetic Ink Character Reader

KeyboardKeyboard

KeyboardKeyboard

ideal for alphanumeric data entryLetter keys : text (word processing)Number keys : spreadsheets)Function keys : shortcutsCursor Keys : menu choiceModifier keys : Shift, Alt, CtrlNOT ideal for graphics

MouseMouse

MouseMouse

Ideal for GUIball transmits XY movementbuttons allow selectionNOT alphanumeric data entry

JoystickJoystick

JoystickJoystick

Ideal for gamesXY axis sensors for movement digital (on / off) : cheap but jerkyanalogue : expensive but smoothbuttons allow selectionNOT alphanumeric data entry

TrackerballTrackerball

– effectively an ‘Inverted mouse’

ideal for portable GUIXY sensors detect ball movementbuttons allow selection

Light PenLight Pen

Light PenLight Pen

Direct screen positioning for GUIbutton for selectionphotosensor detects light spot on VDUscreen position is calculated

Graphics TabletGraphics Tablet

Graphics TabletGraphics Tablet

Used in Computer Aided DesignAllows digitising of imagesIdeal for GUI

Bar Code ReaderBar Code Reader

Data capture in shops and libraries laser beam shines on to bar codewhite bars reflect light to photosensor

9 7 7 0 9 6 3 5 5 2 0 1 4

0 8

Mark Sense ReaderMark Sense Reader

Fast, specialised data captureturnaround documents requiredallows simple manual data entrybrushes passed over documentpencil mark conducts electricity

Optical ScannerOptical Scanner

OCROCR

OCROCR

Data capture direct from writingspecialist fonts : gas meter readerstyped documents read into text fileshand written post codes deciphered

MICR - chequesMICR - cheques

Magnetic Ink ReaderMagnetic Ink Reader

Secure data capture for bankscheques are turnaround documentsdata read by humans and machinecannot be forgedcan be read over patterned cheques

OUTPUT DEVICESOUTPUT DEVICES

Visual Display UnitDot Matrix PrinterDaisywheel PrinterBubblejet PrinterLaser PrinterPlotterVoice Output

Visual Display UnitVisual Display Unit

Dot Matrix PrinterDot Matrix Printer

Daisywheel PrinterDaisywheel Printer

Bubblejet PrinterBubblejet Printer

Laser PrinterLaser Printer

PlotterPlotter

BACKING STOREBACKING STORE

Floppy DiskHard DiskMagnetic TapeWORMCD ROM

Floppy DiskFloppy Disk

Hard DiskHard Disk

Hard DiskHard Disk

Magnetic TapeMagnetic Tape

WORMWORM

Write Once Read Many650MB storageExpensive

CD ROMCD ROM

CD ROMCD ROM

Compact Disc Read Only Memory650MB capacityRead Only

PowerPoint Presentation. 2003PowerPoint Presentation. 2003