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02 - Lossless: RLE and dictionary coding

 1. Lossless compression is a way of reducing the size of files without removing data.

  FALSE

  TRUE

 2. What is RLE?

  Real Level Engineering

  Root Loading Entropy

  Reducing Loss Encoding

  Run Length Encoding

 3. RLE compresses a file by recording values and the number of times they '___'

  repeat

  are deleted

  occur in isolation

  disappear

 4. If the binary value for a green pixel is 00000001 how might RLE represent a row of ten green pixels?

  11000001 00000001

  00000110 0000001

  00001010 00000001

  100000001 00000001

 5. How does dictionary-based compression work?

  By deleting non-essential data

  By replacing each sequence in the data (e.g. strings or bytes) with a codeword

  By deleting alternate sequences of data

  By reading and paraphrasing text

 6. What is a compression dictionary?

  A structure holding data deleted during compression

  A data structure of common sequences or sequences found in the data

  The Oxford English Dictionary

  A guide for users on data compression

 7. Each sequence in the dictionary is given …

  a numerical code

  additional storage space

  a sound wave

  an image

 8. How many different strings could be represented by a 6 bit binary code?

  63

  39

  19

  85

 9. The compression ratio is the ratio between the uncompressed and compressed size of a file.

  FALSE

  TRUE

 10. Variable length encoding (e.g. Huffman coding) improves compression by …

  allocating the shortest codewords to the most common sequences

  utilising online dictionaries

  exacting greater pressure on the data

  deleting sequences that are rarely used


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