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Computer Systems, Speed gets slower as you go down the list …

- - - - Read times are far faster
      - Free space is also in one place so new files do not
        need to be fragmented
- - - - Processors can still only execute instructions in
        machine code
  - - - This makes these languages easier to learn and understand
    - - The translation is done by a program which may be
        either a compiler or an interpreter
- - - - Control Unit
        
        Controls all of the activities taking place within the CPU
        
        Decodes instructions, receives clock signals
      - Arithmetic-Logic Unit (ALU)
      - Registers
        
        The CPU needs to have somewhere to store small amount of data and the results it is operating on
        
        EG, if you wanted to do the calculation 5 + 2 you might do the following
        
        MOVE 5 into register1
        
        MOVE 2 into register2
        
        ADD register1 and register2
        
        1 more item...
      - Cache
        
        Cache is a small amount of a very fast, expensive memory in the CPU
        
        Faster than RAM
      - Clock
        
        The clock controls the timing of the processor
        
        Switches between 0 and 1 several million/billion times a second depending on the peformance of the processor
        
        The clock frequency (clock speed) is the number of clock
        cycles which occur each second
        
        A faster clock speed will result in the faster processing
        of instructions
    - - A bus is a set of parallel wires connecting two or
        more components of the computer
      - When the CPU wishes to access a particular main memory location, it sends the address requested to memory on the address bus
        
        The data in that location is then returned to the CPU on the data bus
      - Address Bus: stores the address of the memory or device
        controller to be read from or written to
      - Data Bus: carries data throughout the computer system
      - Control Bus: uses control signals to control all activities
        within the CPU
      - The CPU is also connected to the external Input-output device controllers by means of the system bus
    - - Clock Speed
      - Cache size
      - Number of Cores
  - - - The program was not stored
- - - - RAM = Random Access Memory
      - Access to RAM is significantly faster than hard drive
      - Volatile storage, meaning all data is lost when powered off
        
        However, all programs and data stored on hard drive will not be loosed when power is off
      - At one time it will usually store:
        
        The OS
        
        The current in use software
        
        The data software is using
    - - ROM = Read Only Memory
      - ROM is used to permanently store data in primary storage, even without power
        
        This means it is non-volatile
        
        Examples of what would be stored are:
        
        The Bootstrap
        
        This is the program that is run that tells the computer where the OS is.
        
        The BIOS
        
        BIOS = Basic Input/Output System
        
        It controls technical configurations like system time, processor clock speed etc.
      - Data on ROM can only be read, not written on
    - - The speed at which data can be accessed changes through different parts of the computer
        
        Processor
        
        Cache
        
        RAM/ROM
        
        Virtual Memory (on HDD)
  - - - DVD
      - CD
      - USB stick
      - HDD
      - SSD
    - - Magnetic
        
        Mechanical parts move over spinning disks and writes data magnetically
        
        Cheap, Large capacities
        
        Mechanical, durability, not very portable
      - Optical
        
        Lasers read and write with light
        
        Data stored as pits and lands burnt or pressed into a track
      - Solid State
        
        Data is recorded onto solid memory chips, no moving parts
        
        Very fast read/write speeds
        
        Uses flash memory to store data