ASCII code for negative acknowledge
21
Negative Acknowledge — a control character, not printable
| Decimal | 21 |
| Hexadecimal | 0x15 |
| Octal | 0025 |
| Binary | 00010101 |
| HTML entity |  |
What it is
A negative reply — the message did not arrive intact, please resend.
The full entry
ASCII 21 in full — the code point page, with what sits either side of it and how the character is encoded elsewhere.
Frequently asked questions
What is the ASCII code for negative acknowledge?
The ASCII code for negative acknowledge is 21 in decimal, 0x15 in hexadecimal and 0025 in octal.
What is negative acknowledge in binary?
00010101 — eight bits, though ASCII only defines seven, so the top bit is always zero.
Is negative acknowledge a printable character?
No. Negative Acknowledge is a control character — an instruction to a teleprinter rather than a mark on paper, which is why most tables show an empty cell for it.
Other characters
- ASCII code for synchronous idle — 22
- ASCII code for end of transmission block — 23
- ASCII code for cancel — 24
- ASCII code for end of medium — 25
- ASCII code for substitute — 26
- ASCII code for escape — 27
- ASCII code for file separator — 28
- ASCII code for group separator — 29
- ASCII code for record separator — 30
- ASCII code for unit separator — 31
- ASCII code for space — 32
- ASCII code for exclamation mark — 33
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