3.3.8 Data compression

• In lossless compression, the original data can be perfectly reconstructed
• Match the type of compression with its typical use:

  Lossless ↔️ Text files

  Lossy ↔️ Multimedia files
• Lossless compression ensures perfect data recovery without significant quality loss
• Match the compression type with its data recovery ability:

  Lossy ↔️ Cannot fully recover data

  Lossless ↔️ Can perfectly recover data
• Compressed data requires less bandwidth to transmit, reducing the time and cost of data transfer over networks.
• Match the compression type with its characteristics:

  Lossless ↔️ Moderate file size reduction, no quality loss

  Lossy ↔️ High file size reduction, quality loss
• Data compression reduces the amount of storage required, allowing more data to be saved on limited media.
• What is data compression used for?

  Reduce data size
• Lossy compression reduces file size more than lossless compression.


  True
• Order the reasons for data compression by importance:

  1️⃣ Storage space

  2️⃣ Transmission time

  3️⃣ Bandwidth conservation
• What is sacrificed in lossy compression to achieve better file size reduction?

  Data quality
• Lossy compression can fully recover the original data.

  False
• Order the benefits of data compression:

  1️⃣ Reduced storage space

  2️⃣ Reduced transmission time

  3️⃣ Bandwidth conservation
• Data compression helps conserve limited network bandwidth, especially for large files or multimedia content.


  True
• Lossless compression ensures perfect data recovery without significant quality loss.
• Run-Length Encoding (RLE) encodes sequences of identical characters as a count and a single character.


  True
• The principle of RLE is to identify and encode runs of the same characters as a count and the character itself.
• RLE is effective for data with long runs of identical characters but ineffective for data with no repeating sequences.


  True
• What is the encoded data for the original data AAABBBCCCDD using RLE?

  3A3B3C2D
• Huffman coding is a lossless data compression algorithm that assigns variable-length codes to characters based on their frequency of occurrence.
• In Huffman coding, more frequent characters receive shorter codes, while less frequent ones get longer codes.


  True
• In Huffman coding, what is the code assigned to the character A if its frequency is 5?

  0
• Match the data compression type with its definition:

  Lossless ↔️ Perfectly reconstructs original data

  Lossy ↔️ Sacrifices some data for greater compression
• Lossless compression is commonly used for text files because it ensures no data is lost during compression.


  True
• What is one advantage of compressed data in terms of transmission time?

  Requires less bandwidth
• Why is data compression important in terms of storage space?

  Reduces storage requirements
• Lossy compression always preserves the original data quality.

  False
• Lossless compression ensures perfect data reconstruction by preserving all data
• Lossless compression is preferred for applications where data integrity is critical.

  True
• RLE is effective for data with long runs of identical characters
• What is a disadvantage of RLE for data compression?

  Not effective for non-repeating data
• The RLE-encoded data for AAABBBCCCDD is 3A3B3C2D.


  True
• In Huffman coding, what type of codes do more frequent characters receive?

  Shorter codes
• Match the compression technique with its principle:

  Run-Length Encoding (RLE) ↔️ Encodes sequences of identical characters as a count and the character itself

  Huffman Coding ↔️ Assigns variable-length codes based on frequency of occurrence
• Data compression helps conserve network bandwidth, which is crucial for efficient communication, especially for large files and multimedia.

  True
• Compressed data requires more bandwidth to transmit than uncompressed data.

  False
• Lossless compression allows perfect recovery of the original data
• What type of file size reduction does lossy compression achieve compared to lossless compression?

  High
• For what type of data is lossy compression commonly used?

  Images and videos
• Huffman coding is a lossless compression algorithm that uses variable-length codes