There is a technical aspect of the GSM encoding that most people doesn't know: It's just 140 bytes. In most encodings (the way computers represent text as 0 and 1) one character of the english language can be seen as a byte, this is because the 8 bits of the byte are used to represent 256 numbers that are mapped to letters, since there is less than 127 characters (leters and symbols) in the english alphabet, the GSM encoding use only 7 bits (less than a byte!) to represent the letters, and taking adventaje of those bits left it finds the way to have 20 more characters than bytes.