Compress .exe files to save space.
Back in 1991 I used a command line program called PKLITE to compress executable files and sometimes to protect code (at least at first). Memory and disk space was at a premium back then and programs were required to be small and fast.
PKLITE was one way to achieve that!
Unfortunately, I do not have any screenshots currently of the file packing from DOS. There are plenty that show a file UNpacking dialog though via Google Image Search.
You can get it here PKLITE!
And documentation is on SCRIBD