Data Storage

• How is analogue sound converted into digital form?

  • Analogue sound wave is sampled
  • Amplitude (of wave) is measured at set time intervals
  • Each sample is stored as a binary number
  • The binary number for each sample is stored sequentially
• What is 12 in binary?

  00001100
• What is binary?

  A sequence of 1s and 0s
• What kind of 'base' system is binary known as?

  Base 2
• What kind of number system is used in everyday life?

  Denary
• What would the denary number 199 be in binary?

  11000111
• What would the denary number 55 be in binary?

  00110111
• What would the denary number 222 be in binary?

  11011110
• What would 10110010 be as a denary number?

  178
• What would 00101110 be as a denary number?

  46
• What would

  00100101

  01000100 +

  be as a binary number?

  01101001
• What is an overflow error?

  When the result of a binary calculation is too long for a computer to process
• What would the hex number 11 be in denary?

  17
• What would the hex number 2B be in denary?

  43
• What would the hex number FA be in denary?

  250
• What would the hex number 11 be in binary?

  00010001
• What would the hex number 2B be in binary?

  00101011
• What would the hex number AA be in binary?

  10101010
•  Perform a binary shift of 2 places left on the binary number 00001110

  00111000
• Binary shift one place left: 00010110

  00101100
• Binary shift one place right: 00010100

  00001010
• Computers work in binary. As a result, all characters, whether they are letters, punctuation or digits are stored as binary numbers. All of the characters that a computer can use are called a character set.
• Two standard character sets in common use are:

  • American Standard Code for Information Interchange (ASCII)
  • Unicode
• ASCII uses seven bits, giving a character set of 128 characters. However, Extended ASCII (which is used in the exam) uses eight bits instead.
• Character set

  A group of characters that a computer recognises from their binary representation.
• How many bits per a character does Unicode use?

  16
• Character sets are logically ordered. The characters are grouped and run in sequence (e.g. is A is 065 then B is 066).
• Which character set can represent more characters- ASCII or Unicode?

  Unicode
• True or False: The first 128 codes in Unicode are the same as ASCII

  True
• Pixels

  Small dots that make up a bitmap image
• Colour depth

  The number of bits used for each pixel
• Most images you use are bitmap images. They're made up of tiny dots, called pixels.

  The colour of each pixel is represented by a binary code. The number of colours available in an image is related to the number of bits the code has.

  
• How can you make a greater range of shades and colours in an image?

  Increase the number of bits for each pixel
• Metadata

  Extra data stored in a file which gives information about the file's properties.
• Resolution

  The number of pixels in a bitmap image
• What will happen if you increase the colour depth of an image?

  • The amount of colours will increase
  • The file size will increase
• What will happen if you increase the resolution of an image?

  • The quality of the image will improve
  • The size of the image file will increase
• What is sample rate measured in?

  Hertz (Hz)
• Duration

  How many seconds of audio the sound file contains
• Bit depth

  Number of bits available to store each sample (e.g. 16-bit)