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Memory and Storage

Lossy and lossless compression

  • 3 things to know
  • J277/01

Overview

Why files are compressed, lossy and lossless compression with their advantages and disadvantages, choosing the right type for spreadsheets, music and X-rays, and common file formats.

What you need to know

Answer each one before you reveal it.

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Key term

Give three common situations where files are compressed

Key term

What is compression?

Key term

Why is compression needed?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is compression?

    Model answer

    Compression reduces the size of a file so that it takes up less storage space. A compressed file is also quicker to send.

  2. 2

    Why is compression needed?

    Model answer

    Compressed files use less storage space on a device. Compressed files also transfer faster over a network and use less bandwidth.

  3. 3

    Give three common situations where files are compressed.

    Model answer

    Photos are compressed so that more fit in a phone’s storage. Music and video are compressed for streaming. Video calls compress sound and pictures so they can be sent live.

  4. 4

    What is lossy compression?

    Model answer

    Lossy compression permanently removes some of the data from a file. The removed data is usually detail that people are unlikely to notice.

  5. 5

    What is lossless compression?

    Model answer

    Lossless compression reduces file size without permanently removing any data. The original file can be rebuilt exactly when it is decompressed.

  6. 6

    State two advantages of lossy compression.

    Model answer

    Lossy compression gives a much smaller file than lossless compression. Smaller files download and stream faster, and more of them fit in the same space.

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