Why historically do people use 255 not 256 for database field magnitudes?

Question

You often see database fields set to have a magnitude of 255 characters, what is the traditional / historic reason why? I assume it\'s something to do with paging / memory l

Answer 1

I think this might answer your question. Looks like it was the max limit of varchar in earlier systems. I took it off another stackoverflow question.

It's hard to know what the longest postal address is, of course, which is why many people choose a long VARCHAR that is certainly longer than any address. And 255 is customary because it may have been the maximum length of a VARCHAR in some databases in the dawn of time (as well as PostgreSQL until more recently).

Are there disadvantages to using a generic varchar(255) for all text-based fields?