ASCII

ASCII, short for American Standard Code for Information Interchange, is a character encoding standard used in electronic communication. It defines 128 code points in seven bits, covering the English alphabet, digits, common punctuation, and a set of control codes. The first 32 codes and code 127 are non-printing controls (such as NUL, BEL, BS, TAB, LF, CR, ESC); the printable characters range from 32 (space) to 126 (tilde).

Developed in the 1960s by committees convened for the American National Standards Institute, ASCII first appeared as ANSI X3.4 in 1963 and was revised in 1967. It aimed to provide a universal text representation that could be exchanged among different machines, terminals, and networks. Its simplicity and portability helped it become a de facto standard for data exchange for decades.

ASCII is the basis for many modern encodings. The seven-bit code is often carried in eight-bit bytes with an additional high bit unused or used for extended code pages, such as ISO 8859-1 or Windows-1252. In Unicode architectures, the ASCII range (0–127) is preserved, and ASCII-compatible encodings such as UTF-8 encode ASCII characters as single bytes.

Today ASCII remains relevant for plain text files, source code, and many Internet protocols (for example, HTTP, SMTP, and TCP/IP payloads). It also supports cultural artifacts like ASCII art. Its limitations—most notably the lack of letters and symbols needed for many languages—help explain the shift to Unicode, though ASCII continues to be a foundational subset of modern character encoding systems.