Run length encoding and Dictionary encoding

• What are the two main types of compression discussed?

  Lossy and lossless compression
• What are the two methods of lossless compression mentioned?

  Run length encoding and dictionary coding
• What type of documents is dictionary coding ideal for?

  Text-based documents
• What type of files is run length encoding more suited for?

  Bitmap images
• How does dictionary coding allow for file recreation?

  By encoding data with an index and unique code
• What does the compressed file consist of in dictionary coding?

  The dictionary index and sequence of occurrences
• How many bits are used per character in 8-bit ASCII encoding?

  8 bits
• How many bits are needed to store numbers 1 to 17?

  5 bits
• What is the main advantage of dictionary coding?

  It allows recreation of the entire message
• What are bitmap images made up of?

  Discrete pixels
• Why is storing binary for each pixel inefficient?

  Many contiguous pixels have the same color
• What color depth is used for the example with two colors?

  One bit
• What do frequency data pairs represent in run length encoding?

  Contiguous pixels of the same color
• What does a frequency data pair like "22 0" indicate?

  22 contiguous white pixels
• How do run length encoding and dictionary coding differ in application?

  • Run length encoding: Ideal for bitmap images
  • Dictionary coding: Ideal for text-based documents
• What are the key components of dictionary coding?

  • Dictionary index
  • Sequence of occurrences
  • Unique codes for data items
• What are the steps to recreate an original file using dictionary coding?

  1. Use the dictionary index
  2. Follow the sequence of occurrences
  3. Reconstruct the original data
• What are the advantages of lossless compression techniques?

  • Original quality is preserved
  • Efficient storage of data
  • Suitable for various file types