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
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
Ideal for GUIball transmits XY movementbuttons allow selectionNOT alphanumeric data entry
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
Direct screen positioning for GUIbutton for selectionphotosensor detects light spot on VDUscreen position is calculated
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
OCROCR
Data capture direct from writingspecialist fonts : gas meter readerstyped documents read into text fileshand written post codes deciphered
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
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