Learn in the textbookData Compression Methods and Characteristics
DefinitionLossless compression (可逆圧縮) is a compression method in which decompression brings back the original data exactly.
ExplanationIt throws away no information and only shortens the way the data is written, so it is used for documents and programs where changing even one character would cause problems. Because nothing is discarded, though, there is a limit to how much it can shrink. Among image formats, PNG and GIF also use lossless compression.
AnalogyIt is like a folding umbrella: it packs down small, yet opens back into exactly the same shape.
Memory hookThe Japanese name 可逆 means "reversible": the process can run back to where it started. The English word "lossless" makes the same point, since nothing is lost.