ASCII 3 — ETX

End of Text (ETX) marks the end of a message body in serial communication, typically paired with STX at the start. More significantly for modern users, Ctrl+C generates ETX and has become the universal keyboard shortcut for interrupting running processes in Unix terminals, Windows command prompts, and virtually every command-line interface. This interrupt behavior is so universally recognized that even non-technical users understand Ctrl+C as the canonical cancel or stop command across all operating systems.

Control characters were defined in the original 1963 ASCII standard to manage telecommunications equipment and terminal devices. Unlike printable characters representing visible symbols, control codes perform actions: initiating transmissions, acknowledging received data, triggering device alerts, and structuring information hierarchically. Of ASCII's 128 code points, 33 are designated as control characters (codes 0–31 plus 127), reflecting the standard's deep roots in telegraphy and serial communication systems. While most control codes have fallen out of daily use, several remain essential to modern computing workflows.

In the ASCII encoding table, End of Text is assigned code point 3 in decimal (0x03 hexadecimal, 003 octal, 00000011 binary). The 7-bit ASCII standard, first published in 1963 by the American Standards Association, defines exactly 128 characters that remain the foundation of text encoding systems worldwide. UTF-8, the dominant encoding on the modern web, is fully backward compatible with ASCII — every ASCII character is encoded as the identical single byte in UTF-8, guaranteeing that End of Text works reliably across all operating systems, programming languages, and internet protocols.