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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?

  Real Level Engineering

  Reducing Loss Encoding

  Run Length Encoding

  Root Loading Entropy

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

  are deleted

  occur in isolation

  disappear

  repeat

 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

  100000001 00000001

  00001010 00000001

 5. How does dictionary-based compression work?

  By deleting non-essential data

  By deleting alternate sequences of data

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

  By reading and paraphrasing text

 6. What is a compression dictionary?

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

  A guide for users on data compression

  The Oxford English Dictionary

  A structure holding data deleted during compression

 7. Each sequence in the dictionary is given …

  a numerical code

  an image

  additional storage space

  a sound wave

 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.

  TRUE

  FALSE

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

  exacting greater pressure on the data

  deleting sequences that are rarely used

  utilising online dictionaries

  allocating the shortest codewords to the most common sequences


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