Octettenpletter
A so-called cruncher for Commodore 64 programs. It utilizes redundancy in files like repeating patterns. To keep the decompressor simple (and fast!) everything is byte-aligned.
Compressed stream
Marker bit: 0/1 (0 = literial, 1 = match)… etc.
Of course if you look for real, faster, better, harder and well-tested compression tools: have a look at exomizer or pucrunch.
What did I learn?
Compression is not an exact science!