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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?

  Reducing Loss Encoding

  Real Level Engineering

  Run Length Encoding

  Root Loading Entropy

 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?

  11000001 00000001

  00001010 00000001

  100000001 00000001

  00000110 0000001

 5. How does dictionary-based compression work?

  By reading and paraphrasing text

  By deleting alternate sequences of data

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

  By deleting non-essential data

 6. What is a compression dictionary?

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

  The Oxford English Dictionary

  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

  an image

  a numerical code

  a sound wave

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

  85

  19

  63

  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

  allocating the shortest codewords to the most common sequences

  exacting greater pressure on the data

  utilising online dictionaries