02 - Lossless: RLE and dictionary coding

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



 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 '___'



  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?





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



 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