ASCII Character: Negative Acknowledge

About the Negative Acknowledge Character

ASCII code 21 (0x15) represents the Negative Acknowledge (NAK) control character. This is a non-printable character defined in the original ASCII standard (1963). It belongs to the communication control group, used in data transmission protocols to manage the flow of information between devices. Control characters occupy codes 0–31 and 127 in the ASCII table and were originally designed for controlling hardware devices, managing communication links, and formatting text output. While many control characters have become obsolete with modern computing, several like LF (Line Feed), CR (Carriage Return), TAB, and ESC remain essential in everyday programming and text processing.

Encoding Details

Source Code Examples

// Using escape sequence
let char = '\x15';
// Using String.fromCharCode
let char2 = String.fromCharCode(21);

# Using escape sequence
char = '\x15'
# Using chr()
char = chr(21)

<!-- Using HTML entity -->
&#21;

// Using escape sequence
char c = '\x15';
// Using cast
char c2 = (char)21;

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