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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.

  TRUE

  FALSE

 2. What is RLE?

  Run Length Encoding

  Root Loading Entropy

  Real Level Engineering

  Reducing Loss Encoding

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

  disappear

  repeat

  are deleted

  occur in isolation

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

  00001010 00000001

  00000110 0000001

  100000001 00000001

  11000001 00000001

 5. How does dictionary-based compression work?

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

  By reading and paraphrasing text

  By deleting alternate sequences of data

  By deleting non-essential data

 6. What is a compression dictionary?

  The Oxford English Dictionary

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

  A guide for users on data compression

  A structure holding data deleted during compression

 7. Each sequence in the dictionary is given …

  additional storage space

  a numerical code

  a sound wave

  an image

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

  63

  19

  85

  39

 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 …

  deleting sequences that are rarely used

  exacting greater pressure on the data

  utilising online dictionaries

  allocating the shortest codewords to the most common sequences


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