The American Standard Code for Information Interchange (ASCII) is a standard table of seven-bit designations for digital representation of uppercase and lowercase Roman letters, numbers and special control characters in teletype, computer and word processor systems. Some IBM systems use similar code called Extended Binary-Coded Decimal Interchange Code (EBCDIC). Since most computer systems use a full byte to send an ASCII character, many hardware and software companies have made their own nonstandard and mutually incompatible extensions of the official ASCII 128-character set into a 256-character set.