What process involves reducing the size of data to save space or speed up transmission?

The process of reducing the size of data to save space or expedite transmission is known as compression. Compression algorithms are designed to encode information using fewer bits than the original representation, which leads to a smaller file size. This reduction in size can significantly enhance storage efficiency and allow for quicker data transfer over networks, as there is less data to send.

Compression can be either lossless or lossy. Lossless compression allows the original data to be perfectly reconstructed from the compressed data, making it suitable for text and some image formats. Lossy compression, on the other hand, reduces file size by removing some data, which can be acceptable for certain applications like audio and video streaming, where a perfect reproduction of the original is not critical.

The other processes mentioned serve different purposes. Decompression refers to the process of returning compressed data back to its original state, encoding is about transforming data into a different format for specific use cases (like for transmission or storage), and encryption is focused on securing data by converting it into a coded format that can only be read by authorized users. Thus, compression specifically addresses the need to save space and improve transmission times.