Title: Year 12 / Computer Science / Theory / 1 - Information Representation / 1.3 - Compression

Q: State what is meant by file compression
A: process of reducing file size without significant loss in quality

Q: State the advantages of file compression
A: reduces time taken to search for data,
allows for faster transfer of compressed files which uses less bandwidth than uncompressed files

Q: State what is meant by lossless compression
A: type of compression that allows original data to be perfectly reconstructed from a compressed file when the file is opened by utilising some type of replacement

Q: Explain what run length encoding is
A: form of lossless compression used to compress text files and bitmap images, reduces file size of sequence of elements which have adjacent identical elements, repeating sequence of elements is encoded in 2 values, run count and run value

Q: State what is meant by lossy compression
A: type of compression that irreversibly eliminates unnecessary data

Q: Describe the advantages and drawbacks of lossy compression compared to loseless compression
A: file accuracy and quality is lower, but file size is lower by about 10%

Q: Explain how sound files use lossy compression
A: they use perceptual coding to remove certain parts of sound that is less audible or discernible to human hearing

Q: State examples and file types, and file extensions, that use loseless compression
A: bitmap .bmp, vector graphic .svg, .png images, text file compression, database records

Q: State file types, and file extensions, that use lossy compression
A: sound files and jpeg images