ASCII Character ␑

The Device Control One character (␑), also known as XON, is a control character in the ASCII and Unicode character sets with the value of 17. It is often represented as DC1 in ASCII and U+0011 in Unicode.

• The Device Control characters (DC1, DC2, DC3, DC4) were originally designed to provide additional control functionality in device communications.
• DC1 (XON) along with DC3 (XOFF) are commonly used for software flow control in telecommunications and in certain file transfer protocols. This mechanism is also known as XON/XOFF flow control.
• In the XON/XOFF protocol, the XOFF character is used to tell the device to stop sending data (it's essentially saying "I'm full, stop sending"), and the XON character is used to tell the device to resume sending data (it's saying "I'm ready for more data, you can send now").
• Like other ASCII control characters, DC1 (XON) does not represent a printable glyph and is typically non-visible in text content.
• In the context of modern computing and telecommunications, the use of XON/XOFF flow control has been largely replaced by hardware-based flow control mechanisms, but it may still be used in certain situations where hardware-based flow control is not feasible or practical.