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Logical Computer System

Logical Computer System

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Logical Computer System

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  1. Logical Computer System Unit 2, Introduction to Computer Systems

  2. Logical vs. Physical • A computer system can be represented in either a logical or physical form • Both are useful in understanding Computer Systems theory. Logical Computer System Presentation Unit 2

  3. Physical Computer System • The actual hardware as seen in real life • Contains micro-electronics and physical mechanisms • Powered by electricity • Very detailed and complex • Difficult to fully understand without a working knowledge of electronics. Logical Computer System Presentation Unit 2

  4. Logical Computer System • A basic model of a computer system • The model is built from a number of different blocks • Each block performs a different task • All blocks work together to process data into information • Model is conceptual – could not be physically the same in real-life • Less complex, easier to understand. Logical Computer System Presentation Unit 2

  5. Logical Computer System CPU Control Unit ALU Input Device Main Memory Output Device Backing Storage Test me! Logical Computer System Presentation Unit 2

  6. Input Device • A device which lets the user “feed” data into the computer • Converts data into a stream of electronic digital signals • Digital signals will be converted into binary inside the computer • Some sample real-world input devices; keyboard, mouse, light pen, scanner, microphone, camera, motion sensors, biometric devices such as a fingerprint scanner, OMR/OCR readers for direct data capture etc. Logical Computer System Presentation Unit 2

  7. Main Memory • Stores data before being processed by CPU • Stores program being executed by computer • Is volatile - when power is removed, data is lost • Often called “RAM” - Random Access Memory • Stores processed data before it is output • Contents are filled by Input Devices, Backing Storage or the CPU • Data that needs to be saved (for future use) is written to the backing storage. Logical Computer System Presentation Unit 2

  8. Backing Storage • Usually non-volatile, although its contents may be deleted • Loads previously stored data into the main memory • Loads previously written programs into memory for processing by CPU • In the real world may be internal or external • Usually mechanical (eg Hard Drive, CD or DVD Writer) which slows a computer system • Data is usually “read” (loaded) or “written” (saved). Logical Computer System Presentation Unit 2

  9. Output Devices • Converts processed data, stored in main memory, into a form that can be understood by a human as information • Some sample real-world output devices; monitor (CRT or TFT/LCD), speakers, printer, plotter, robot, etc. Logical Computer System Presentation Unit 2

  10. CPU • CPU is an abbreviation of Central Processing Unit • The CPU is often called the Processor • The CPU is the computer’s brain • The speed of the CPU generally determines the efficiency and power of the computer system • The CPU consists of two sub-systems: The ALU (Arithmetic/Logic Unit) and the Control Unit. The former performs basic calculations and logical comparisons. The latter co-ordinates and runs the computer’s operations. Logical Computer System Presentation Unit 2

  11. Activity Complete the worksheet activity by identifying the correct components on the logical computer system model. Logical Computer System Presentation Unit 2