ASCII usually uses 7 binary digits (bits) to represent characters: 1000001 (or 41 in hexadecimal or 65 in standard base-10 numbers) represents the upper-case letter A; 1000010 represents B; 1000011 represents C; and so on in sequence. Eight bits allowed a "parity bit" to be included in each byte sent over a serial port or modems, this bit is used for avoiding errors. This was more important years ago when connections were often noisy.