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  • Created by: Zoe16
  • Created on: 04-04-15 17:24

Central processing Unit (CPU)

Hardware- The physical componenents of a computer system.  ..... seen ot touched

Components include:

  • Input 
  • Output
  • Storage
  • Processing devices


Arithmetic & Logic Unit - Carries out all the maths and logical operations

Control Unit- Uses electrical signals to control the flow of data within the CPU. 

Fetch ----------Decode ----------Execute 

  • Fetch Instruction from memory
  • Decode instruction to find out what processsing is necessary 
  • Execute the intruction
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CPU Features

The Boot Sequence- sequnce of processes, containing all the information to get the computer up and running. 

After booted the control is handed to the operating systems.

The speed of the CPU depends on :

CPU Clock Speed- determined by the electric clock chip. 

  • Measured in cycles per second- Hertz (Hz)
  • Processor speeds are measured in gigahertz (GHz)--- billion cycles/ second

Cache Memory = expensive 

Number of Processor Cores- Multi-cores have multiple cores working together.

The CPUs can fetch----decode-----exectute instructions at the same time.

  • More data processed simultaneously  
  • However complocated operating systems are needed to manage them. 
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RAM ( Random Access Memory) 

  • Volitile 
  • Accessed and changed by computer at any time
  • Contains operating system 
  • Stores programs and data used by computer
  • Large

ROM (Read Only Memory)

  • Non-volitile
  • Programed during comouter manefacturing
  • Contains Boot Program
  • Stores instruction and data used to start comouter
  • Small 
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Memory Cont...

Virtual Memory 

  • An extention to RAM - part of the harddrive
  • Used when not enough RAM to hold programs and data required
  • Access to V memory = slower than to RAM 
  • More RAM = > use of V memory= Improved performance of computer

Flash Memory 

  • Type of ROM that can be Re- written
  • Used as a portable medium for storing & transferrign data
  • Examples;  USB memory stick, Camera memory cards  
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Input devices

Input devices:

  • Keyboard - data entry into computer
  • Mouse - controls pointer 
  • Touch Screen - user interacts directly with icons. 
  • Microphones - Uses voice input 
  • Camera - Captures image or video 
  • Bar Code Scanner Reads light reflected back from pattern
  • RFID reader - reads data from electronic version of a bar code
  • Sensor- detects physical conditions i.e light, temperature
  • Eye-typer - camera tracks movement of eye 
  • Foot Mouse - Track ball operated by foot 
  • Puff-Stick -blowing into small tube  
  • Braille Keyboard - Keys with embosed patterens for the blind
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Output devices

Output devices:

  • Monitor - displaying text, images etc. 
  • Printers - Produce copy on paper 

e.g. Inkjet, 3D printers, Thermal printers

  • Plotter - Large scale architectual drawings 
  • Speakers - Sound output 

e.g. Music, Warning sounds, Comunnication, Synthetic voice (SIRI)

  • Actuators - Physical responce to computer command

e.g. Robots, Wheelchairs 

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Secondary storage

Magnetic Hard Disk- Stores operating system, installed programs & user data

  • Reliable 
  • High Capacity
  • Low Cost

Optical Disk- Transfers files or distributes software 

  • Good Capacity 
  • Low Cost 
  • Lightweight & portable 

Flash Memory-  comsumes little power

  • Good Capacity  but < hard disk 
  • Used in hand held devices 
  • >expensive than hard disks 
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