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

Data is saved in memory in binary system and 0 and 1 are binary digits. Largest binary number that can fit in 1 byte (8-bits) is 11111111 which converts to decimal 255.