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

255 was the varchar limit in mySQL4 and earlier.

Also 255 chars + Null terminator = 256

Or 1 byte length descriptor gives a possible range 0-255 chars