output is created, it is immutable. If it needs to be changed, either an update must be appended or a new version must be created. [Archives] 
n., The way in which the information in a file is encoded. There are many proprietary formats – nearly every application has its
own, often changing with new versions – as well as standard file formats such as RTF, TIFF, and EPS. In some systems, such as
Apple Macintosh, the information about file format and originating application is part of the file, but in other s