A character encoding scheme used by many computers is ASCII, the American Standard Code for Information Interchange. ASCII assigns numeric codes to letters, digits, punctuation marks, and control instructions so computers can represent and exchange text.
The original ASCII standard uses 7-bit codes and defines 128 values. These include 95 printable characters, such as the uppercase and lowercase English alphabet, and 33 control characters used for functions such as line feeds and device communication.
ASCII was designed primarily for English-language text, so it cannot represent most accented alphabets or writing systems such as Chinese, Arabic, or Devanagari by itself. Modern Unicode preserves ASCII’s first 128 code points, which is why ordinary English letters and punctuation remain compatible across many computer systems. “Extended ASCII” is a common informal term for several different 8-bit encodings, not one single universal standard.