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Computer Science - Coggle Diagram

- - - - volatile
        
        loses everything when the power is turnt off
      - ROM is non-volatile memory which stores things like the BIOS
      - Virtual memory is used as RAM when The RAM is full virtual memory is located on the hard disc drive
      - RAM is volatile memory that deals with programs that are currently in use
    - - magnetic storage stores data in domains some of its advantages is that it has a huge capacity and the cheapest per GB but it has moving parts and a magnetic field will erase all data
      - Optical storage stores data in pits which are cut by a laser optical storage is portable and it has a low cost for storing small amounts but it is not very robust and slow to access and write data on to it and its cost is high for large amounts of data
      - solid state storage holds data using electronic switches it is very portable robust and data can be access very fast but its very expensive and you can only change the data on it for a limited amount of times
    - - a bit is a single binary 1 or 0
      - a nibble is 4 bits
      - a byte is 8 bits
      - a kilobyte is 1024 bytes
      - a megabyte is 1024 kilobytes
      - a gigabyte is 1024 megabytes
      - a terabyte is 1024 gigabytes
      - a petabyte is 1024 terabytes
    - - characters
        
        character sets are a set of binary values which makes up letters symbols and words there are 3 types
        
        Extended ASCII-256 possible characters
        
        Unicode-65,000+ characters
        
        ASCII-127 possible characters
      - images
        
        Color depth is the amount of colors used in an image
        
        a pixel is a picture element which is very small and lots together make up pictures
        
        resolution is the amount of pixels in an image 32 x 32 just means 32 pixels wide and 32 pixels high
      - numbers
        
        Binary is the language of a computer on how it understands what to do. binary is only made up of 1's and 0's and binary is a base2 system because it goes up 2times every time
      - sound
        
        analogue sound is the sound that humans hear
        
        anolgue sound is turned digital using an Analogue to digital converter (AD)
        
        a sample is a recording at certain time intervals
        
        the sample rate is how many samples are taken per second
        
        bit depth is the number of bits used to record each sample
    - - lossy compression
        
        this is when you sacrifice some of the quality of the image to save storage space
        
        before compression
        
        after compression
      - lossless compression
        
        this is when you delete all of the unnecessary parts of the image to save space but the quality stays the same
        
        before compression
        
        after compression
  - - - 1.3.1 Networks and topologies
        
        A computer network is 2 or more devices connected together
        
        computer networks are useful because you can easily share documents software and devices
        
        LAN is a collection of devices connected together in a small space.
        
        WAN is 2 or more LAN's connected together over a large geographical area. for example a LAN in London and a LAN in New York connected together is a WAN.