ASCII 6
ASCII 6 is Acknowledge — the control character ACK.
Every representation
| Character | ACK (not printable) |
| Name | Acknowledge |
| Decimal | 6 |
| Hexadecimal | 0x06 |
| Octal | 0006 |
| Binary | 00000110 |
| HTML entity |  |
| Escape sequence | \x06 |
| Unicode | U+0006 |
| Keyboard | Ctrl+F |
| Group | Control character |
What it is for
A positive reply — the message arrived intact. The name lives on in networking, where a TCP ACK does the same job with a different encoding.
Where the number comes from
Codes 0 to 31 were reserved for control: instructions to a teleprinter rather than characters to print. Code 6 is Ctrl+F because the Ctrl key was originally wired to clear the top two bits of whatever you typed, mapping the letter F at 70 down to 6.
Frequently asked questions
What is ASCII 6?
Acknowledge (ACK), a control character. In hexadecimal it is 0x06, in octal 0006, and in binary 00000110.
How do I type ASCII 6?
Press Ctrl+F in a terminal. In a string literal you can write it as \\x06 in most languages.
Is ASCII 6 printable?
No. Codes 0 to 31 and 127 are control characters — they were instructions to a teleprinter rather than marks on paper, and most terminals show nothing for them.
Nearby codes
- ASCII 0 — NUL
- ASCII 1 — SOH
- ASCII 2 — STX
- ASCII 3 — ETX
- ASCII 4 — EOT
- ASCII 5 — ENQ
- ASCII 7 — BEL
- ASCII 8 — BS
- ASCII 9 — HT
- ASCII 10 — LF
- ASCII 11 — VT
- ASCII 12 — FF
- ASCII 13 — CR
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