Students should understand that it is common for data to be compressed and…

The idea

Compression is used routinely because smaller files are cheaper and faster to handle. Storing a file uses less secondary storage, so more data fits on a disk or in cloud storage. Sending a smaller file over a network uses less bandwidth and downloads or uploads more quickly, which matters for streaming video or transferring photos. Smaller files also reduce the time needed to back up or copy data. Recognise that compression is common because these benefits apply to almost every type of digital file.

What earns the marks

• Compressed files need less secondary storage, so more data can be held.
• Smaller files transfer faster over a network and use less bandwidth.
• Reducing file size saves time when copying, backing up or downloading data.
• Compression is common because these benefits apply widely to many file types.
• A correct MCQ choice names a real benefit such as reduced storage or faster transmission, not improved quality.

Common mistakes and how to put them right

• Claiming compression improves the quality or resolution of an image.

  Put it right: Compression reduces file size and may reduce quality in lossy methods, but never improves it.

• Thinking compression increases the amount of data stored.

  Put it right: It reduces the bits needed, allowing more files to fit in the same storage.

• Ignoring network benefits and only mentioning storage.

  Put it right: Faster transmission and lower bandwidth use are equally valid reasons to compress data.

Exam tips

• Look for options naming storage saving, faster transfer or reduced bandwidth.
• Reject options that claim compression increases quality or data quantity.
• Match the reason given to a real benefit such as fitting more files on a disk.