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Hardware Overview

Hardware Overview. CS French Chapter 11. Main Functional Elements of a Computer System. Input / Output (I/O) to give out information to take in data and instructions Storage Memory (main storage) holding current data and instructions

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Hardware Overview

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  1. Hardware Overview CS French Chapter 11

  2. Main Functional Elements of a Computer System • Input / Output (I/O) • to give out information • to take in data and instructions • Storage • Memory (main storage) • holding current data and instructions • Auxilliary Storage (not part of the main functional elements but included here to remind you that it is different from main storage) • supplement to main storage • less expensive, bigger capacity, non-volatile, slower. • Processing • Arithmetic and Logic Unit (ALU) • calculations and comparisons • Control Unit • interprets and carries out instructions.

  3. Elements of a Computer System Computer Peripheral Devices Keyboard Screen Mouse Printer Plotter Modem Floppy disk drive Hard disk Compact disk Magnetic tape Network ‘card’ Processor Input/ Output unit Memory (RAM) Control Unit ALU data bus Classify ‘peripherals’ as input, output, auxialliary storage or communication devices!

  4. A Human as a Computer • Name examples of each type of device! • Input • Output • Main Memory • Auxilliary Storage • Control Unit • ALU (Arithmetic and Logic Unit)

  5. Input Devices • Keyboard • Mouse • Bar code readers • Voice data entry • Sensors ( eg. temperature sensor) + Analog/Digital converter

  6. Output Devices • Printers • Ink Jet • Laser • Plotters (13.48...) • Generally like large ink – jet printers • Screen (VDU) • Actuators + Digital/Analog converters (eg. robotic hand) Faster

  7. On-line Process Control Analog data Analog to digital converter Vessel which must have its temperature controlled Electrical thermometer (sensor) Input Digital Computer Digitally operated motor switch Output Coolant tap driven by a motor (actuator) Digital control signal Fig 13.8

  8. Main Storage (memory) • Semi-conductor memory (RAM) • E.g. charged cells • Raandom Access Memory: RAM (constantly refreshed) • Battery backed RAM • ROM: Read Only Memory, set at manufacture

  9. Auxilliary Storage • Magnetic Disk • fixed/exchangable (online/off line) • hard/flexible (floppy) • Magnetic Tape • cassette, cartridge, Digital Audio Tape • Optical Disk • CDROM • WORM – write once read many times • EO – erasable optical – re-writable CD • DVDROM – very high capacity • Solid State Backing storage devices Which of the above are direct access and which are serial access devices? (A serial access device requires that you read through all the preceeding data until you get to what you want. Think about serial/direct access to music)

  10. Measurement of Storage • Bit - smallest unit of storage • Byte = 8 bits • Kilobyte (Kb) 1024 bits (K = 210 = 1024) • Megabyte (Mb) = 1024Kb • Gigabyte = 1024 Mb • 1000 is an acceptable approximation for K • eg 2Mb = 2,000,000 bytes

  11. A Program to add up a set of numbers. The computer’s screen should look like this: Type in the numbers now (Remember to type 999 to stop) number =? 5 number =? 4 number =? 7 number =? 1 number =? 999 total = 17

  12. Preparing the Human Computer • Problem • How to add up a set of numbers and produce a total. • Solution • a set of instructions in the computer’s own language (program) • english in the case of a ‘human computer’ • Program is fed into your memory • Instructions are obeyed • program ‘run’ or ‘executed’

  13. The ‘Program’ 1. Start with total of zero. 2. Set a ‘signal’ value to 999 3. Take a number from the input list. 4. If the number is equal to the signal value then go to instruction 7 5. Add the number to the total 6. Go back to instruction 3 7. Print the total 8. Stop

  14. Testing the program(dry run) Program Trace

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