Negative Acknowledge

U+0015
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Symbol Meaning

The Negative Acknowledgement symbol was used in computer terminals, printers, text processing systems, and telecommunication equipment to control data flow and ensure the reliable transmission of information.

It tended to indicate an error in data transmission or a problem with receiving information. In communication protocols, after receiving the NAK symbol, the data sender was required to repeat the previous transmission to correct any errors or data loss. If the data was transmitted correctly, the opposite symbol was sent ( Acknowledge).

As for modern computer systems and applications, the U+0015 symbol is rarely used there, since other mechanisms and protocols are employed to ensure the reliability of data transmission and error handling.

Like many other control symbols, this one has no visible representation and doesn't occupy a lot of space on screen or in typed text. However, there is a separate symbol in Control Pictures2400–243F representing the graphical image of the Negative Acknowledge symbol as the abbreviation NAK — .

The symbol “Negative Acknowledge” is included in the “C0 controls” subblock of the “Basic Latin” block and was approved as part of Unicode version 1.1 in 1993.

Text is also available in the following languages: Русский;

Synonyms

NAK.

Unicode Name Negative Acknowledge
Unicode Number
HTML Code
CSS Code
Unicode Block Basic Latin
Unicode Subblock C0 controls
Unicode Version 1.1 (1993)
Keyboard shortcut ^U
Version 1.1
Block Basic Latin
Type of paired mirror bracket (bidi) None
Composition Exclusion No
Case change 0015
Simple case change 0015
age 1.1
scripts Common
Encoding hex dec (bytes) dec binary
UTF-8 15 21 21 00010101
UTF-16BE 00 15 0 21 21 00000000 00010101
UTF-16LE 15 00 21 0 5376 00010101 00000000
UTF-32BE 00 00 00 15 0 0 0 21 21 00000000 00000000 00000000 00010101
UTF-32LE 15 00 00 00 21 0 0 0 352321536 00010101 00000000 00000000 00000000
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