What does it mean if a file is compressed?

When a file is compressed, it means that the data within the file has been altered in a way that reduces its overall size. This is achieved through various algorithms that eliminate redundancy and utilize more efficient coding of the information. Compression allows for more efficient storage and faster transmission over networks, as smaller files take up less space and bandwidth.

The process can be lossy or lossless. In lossless compression, the original data can be perfectly reconstructed from the compressed data, while in lossy compression, some data is lost, which may be acceptable depending on the file type and intended use.

The other choices do not accurately describe compression. Updating in real-time pertains to file modification rather than size reduction, sharing over a network pertains to distribution rather than the file size itself, and saving in a non-editable format refers to restricting edits rather than reducing file size. Therefore, the correct understanding of compression is that it specifically focuses on reducing the size of the file through manipulation of its data structure.