ASCII 18 — DC2

Device Control 2 (DC2) was reserved for controlling auxiliary devices connected to a terminal or communication system. Unlike DC1 (XON) and DC3 (XOFF) which became standardized for flow control, DC2 was left for device-specific implementations as determined by each manufacturer. Various hardware vendors assigned proprietary meanings to DC2 in their protocols during the early decades of computing. Generated by Ctrl+R, the character is largely unused in modern systems though some legacy industrial and point-of-sale equipment still references it.

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, Device Control 2 is assigned code point 18 in decimal (0x12 hexadecimal, 022 octal, 00010010 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 Device Control 2 works reliably across all operating systems, programming languages, and internet protocols.