Data Representation

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  • Created by: millard
  • Created on: 08-05-16 11:58

ASCII & Unicode


  • Each character has been assigned a 7 bit binary string in the ASCII table, e.g. 'A' 100 0001
  • ASCII stands for American Standard Code for Information Interchange
  • ASCII is standardised which means that all comptuters can understand downloaded documents, for example, as they all decode the binary into characters using the same table
  • However, the problem with ASCII is that it can only fit 128characters
  • Whereas, extended ASCII can fit 256 characters, as it is 8bit 
  • Unicode was added so that characters from languages all around the world can be universally understood, it is an extension of ASCII that stores characters as 16bit binary, which allows for 65,536 different characters
  • Therefore, the greater the number of bits per character in a character set the greater the number of characters that can be represented
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  • Images are stored as a series of 1's and 0's
  • A pixel is the smallest picture element
  • The resolution is how many pixels there are usually per inch of the screen
  • The higher the resolution the higher the fidelity, this is because there are smaller 'squares' in the overlay of the original picture, so when it is digitalized and the combination of all of the colours in each square is produced there will be a more accurate representation of the colour; however there will also be an increased file size
  • Colour/bit Depth - is the number of bits that are avaliable to represent colour, for example the normal bit depth used in digital images, is 24bits which means there are 8 bits avaliable for Red, Green and Blue; there are 256 colour variations for each so the fidelity is increased
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  • Instructions are made up of three parts: the Op-code. the number bit and the operand
  • Op-code - is the process that is going to be carried out, e.g. add
  • Number bit - is used to indicate whether the data in the operand is a value or address
  • Operand - contains the data that is going to be processed
  • An 8 bit instruction looks something like this: 010 1 0001
  • The instructions are processed by the CPU, an instruction is fetched to the CPU and the instructions is sent to different sections of the CPU where it is decoded and then the instruction is executed
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