ASCII 5 — ENQ

Enquiry (ENQ) was used in polling protocols to request a response from a remote station. A sending device would transmit ENQ to ask 'are you ready?' and the receiver would respond with ACK or NAK accordingly. This simple handshake mechanism predates modern networking protocols by decades but established the request-response pattern. ENQ is still encountered in some legacy industrial equipment, point-of-sale systems, and mainframe communication protocols. The Ctrl+E keyboard shortcut generates this character.

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, Enquiry is assigned code point 5 in decimal (0x05 hexadecimal, 005 octal, 00000101 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 Enquiry works reliably across all operating systems, programming languages, and internet protocols.