A JPEG decoder or TCP stack are very clearly not individual concepts though. There's obviously some subjectivity as to what constitutes a single "concept" or "a

A JPEG decoder or TCP stack are very clearly not individual concepts though. There's obviously some subjectivity as to what constitutes a single "concept" or "algorithm", but I'm not sure either of those two examples are in a gray area. A single concept might be implementing just ARP or a discrete cosine transform. If you wanted to do a full TCP stack or JPEG decoder, that would make a lot more sense after building their internal components one by one.