A normal byte consists of 8 bits, meaning 8 0s or 1s, this means it can be anything from 00000000 to 11111111. These are just binary numbers, and binary 00000000 is normal (decimal) 0, and 11111111 is decimal 255. So one byte can be any number from 0 to 255. If you don't understand binary, please look at http://en.wikipedia.org/wiki/Binary_numeral_system