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The Computer

The Computer. an electronic data processor. Computer Systems. many systems have this structure. INPUT. PROCESS. OUTPUT. BACKING STORE. Computer Hardware. hardware is anything tangible : Central Processing Unit this is inside the main box Peripherals

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The Computer

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  1. The Computer • an electronic data processor

  2. Computer Systems • many systems have this structure INPUT PROCESS OUTPUT BACKING STORE

  3. Computer Hardware • hardware is anything tangible : • Central Processing Unit • this is inside the main box • Peripherals • these are devices attached to the CPU

  4. Peripheral 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

  5. INPUT DEVICES • Keyboard • Mouse • Joystick • Trackerball • Light Pen • Graphics Tablet • Bar Code Reader • Mark Sense Reader • Optical Scanner • Magnetic Ink Character Reader

  6. Keyboard

  7. Keyboard • ideal for alphanumeric data entry • Letter keys : text (word processing) • Number keys : spreadsheets) • Function keys : shortcuts • Cursor Keys : menu choice • Modifier keys : Shift, Alt, Ctrl • NOT ideal for graphics

  8. Mouse

  9. Mouse • Ideal for GUI • ball transmits XY movement • buttons allow selection • NOT alphanumeric data entry

  10. Joystick

  11. Joystick • Ideal for games • XY axis sensors for movement • digital (on / off) : cheap but jerky • analogue : expensive but smooth • buttons allow selection • NOT alphanumeric data entry

  12. Trackerball • effectively an ‘Inverted mouse’ • ideal for portable GUI • XY sensors detect ball movement • buttons allow selection

  13. Light Pen

  14. Light Pen • Direct screen positioning for GUI • button for selection • photosensor detects light spot on VDU • screen position is calculated

  15. Graphics Tablet

  16. Graphics Tablet • Used in Computer Aided Design • Allows digitising of images • Ideal for GUI

  17. 0 8 9 7 7 0 9 6 3 5 5 2 0 1 4 Bar Code Reader • Data capture in shops and libraries • laser beam shines on to bar code • white bars reflect light to photosensor

  18. Mark Sense Reader • Fast, specialised data capture • turnaround documents required • allows simple manual data entry • brushes passed over document • pencil mark conducts electricity

  19. Optical Scanner

  20. OCR

  21. OCR • Data capture direct from writing • specialist fonts : gas meter readers • typed documents read into text files • hand written post codes deciphered

  22. MICR - cheques

  23. Magnetic Ink Reader • Secure data capture for banks • cheques are turnaround documents • data read by humans and machine • cannot be forged • can be read over patterned cheques

  24. OUTPUT DEVICES • Visual Display Unit • Dot Matrix Printer • Daisywheel Printer • Bubblejet Printer • Laser Printer • Plotter • Voice Output

  25. Visual Display Unit

  26. Dot Matrix Printer

  27. Daisywheel Printer

  28. Bubblejet Printer

  29. Laser Printer

  30. Plotter

  31. BACKING STORE • Floppy Disk • Hard Disk • Magnetic Tape • WORM • CD ROM

  32. Floppy Disk

  33. Hard Disk

  34. Hard Disk

  35. Magnetic Tape

  36. WORM • Write Once Read Many • 650MB storage • Expensive

  37. CD ROM

  38. CD ROM • Compact Disc Read Only Memory • 650MB capacity • Read Only

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