What's the meaning of ad-hoc character code?

Question

Reading this, http://www.wps.com/J/codes/:

Murray's code is the last ad-hoc character code of historical note in this thread

When hearing "ad-hoc", the wireless network comes into my mind. But what's the meaning of "ad-hoc character code"?

Answer 1

The larger quote is:

Murray's code is the last ad-hoc character code of historical note in this thread; at this point, telegraphy networks were large enough to not tolerate hacker meddling with "better" systems, instead favoring lumbering, international-committee codes with infrequent change.

The context here is important. Here, "ad-hoc" seems to take its standard English meaning: "for the particular end or case at hand without consideration of wider application". So, Murray's code was developed by the seat of, presumably Murray's pants, quickly and without much investigation, rather than as the end result of a detailed requirements study.