ASCII 22 — SYN

Synchronous Idle (SYN) maintained clock synchronization between sender and receiver in synchronous serial communication when no actual data was being transmitted. Unlike asynchronous communication which uses start and stop bits per character, synchronous protocols required continuous signaling, and SYN characters filled the idle gaps to keep the clocks aligned. Ctrl+V generates SYN in raw terminal mode, though most modern applications intercept Ctrl+V for paste functionality long before the raw control character reaches the underlying system.

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, Synchronous Idle is assigned code point 22 in decimal (0x16 hexadecimal, 026 octal, 00010110 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 Synchronous Idle works reliably across all operating systems, programming languages, and internet protocols.