ARJ (Archived by Robert Jung) is a high efficiency compressed archive file developed by Robert K. Jung. ARJ was developed for DOS and early versions of Windows in the early 1990s. ARJ files are useful for backing up or sharing a large number of files as you do not have to keep track of all those files and there is only a single file to handle. The .arj extension is used for the ARJ archive files.
ARJ File Format
An ARJ file contains two types of headers:
Main header: There is one main header at the start of the archive.
Local headers: Local headers are present before each file.