1.4 Data types, data structures and algorithms

• Give one similarity between ASCII and Unicode

  • Both (use binary) to represent characters
  • Both are character sets
  • The first 7/8 bits of Unicode is the same as ASCII (overlaps)
• Give two differences between ASCII and Unicode

  • ASCII has fewer characters (128/256)
  • Unicode has more characters
  • ASCII is 7/8 bits whereas Unicode can be larger 16/32 / can have variable sized characters
  • ASCII limited to Latin / English / European characters
  • Unicode can represent other symbols (e.g. Chinese/Emojis)
• Compare the efficiency of a binary search tree to a linked list when searching for data.

  • Binary tree more efficient than linked list
  • Does not need to check every value
  • tree removes half values each time
• Describe a mask that could be applied to an 8-bit number to ensure that:

  • the most significant bit is always set to 1
  • all other bits remain unchanged
  • 1000 0000
  • OR
• State the purpose of a D-type flip-flop circuit

  • Delay / store a value of 1 bit when a signal is given
• Describe the inputs and outputs used by a D-type flip-flop circuit, explaining how the inputs are used to control the outputs.

  • Data input
  • Clock input
  • Q output When clock input goes high
  • Q changes to D
  • NOT Q is reverse of Q
• The database previously stored reviews using the ASCII character set. ASCII uses 1 byte per character. It is decided to switch to the Unicode UTF-32 character set which uses 4 bytes per character.

  Give an advantage and disadvantage of changing character sets from ASCII to Unicode UTF-32.

  Advantage

  • More characters can be represented
  • may include foreign alphabets
  • may include emojis

  Disadvantage

  • Reviews take up more storage (4 times their previous storage size)
• A programmer is writing software for a firewall. The following data is also stored about each website: • Access level needed (1-4) • If it is available all the time (true) or just lunch times and out of work hours (false). So a website which is available to users of access level 2 and above, all the time, would have the details [2, true] stored. A website accessible to users of access level 3 and above, only outside of work hours, would have the details [3, false] stored.

  State the name of a data structure that could be used to store a single site’s details.

  • tuple /record /list
• Describe what is meant by the term ‘ASCII’.

  • American Standard Code for Information Interchange
  • A character set
  • Maps values to characters
  • Uses 7-bits/ 8-bits per character
• Describe what is meant by the term ‘linked list'

  • A dynamic/data structure
  • Each node/item consists of data and pointer
  • Pointer gives location of next node.
• A coach company offers tours of the UK. The tour is amended. The new itinerary is: London, Oxford, Manchester then York.

  Explain how Birmingham is removed from the linked list and how York is added. You may use the diagram below to illustrate your answer.

  • Oxford pointer changed to bypass Birmingham and point to Manchester.
  • A node is created holding the data York/York is placed is next free space/node/item
  • Manchester remains in original position and pointer changed to point to the York node.
  • The York node points to null (or terminator).