31
US
0x1F · 0011111
ASCII 31 — the US character
Not a visible character
US is control code 31, hex 1F. You type it as ^_, and it draws nothing on screen.
Characters that draw nothing and instead tell the device to do something.
What this control code did
Unit separator
Separators · Four nested separators: file, group, record, unit.
Seven bits
ASCII is seven bits wide, which is why there are 128 of them. The eighth bit was long left for parity.
0011111
One bit — the sixth, worth 32 — separates the cases. Off gives a capital, on gives a lowercase letter.
- Kind
- Control
- Decimal
- 31
- Hexadecimal
- 0x1F
- Octal
- 037
- Binary
- 0011111
- HTML entity
- 
- URL encoding
- %1F
- CSS escape
- \1F
- Ctrl key
- ^_
The chart
Eight columns for the top three bits, sixteen rows for the bottom four. The capitals column sits right beside the lowercase one — that is the shape of the table.
0NUL1SOH2STX3ETX4EOT5ENQ6ACK7BEL8BS9HT10LF11VT12FF13CR14SO15SI16DLE17DC118DC219DC320DC421NAK22SYN23ETB24CAN25EM26SUB27ESC28FS29GS30RS31US32SP33!34"35#36$37%38&39'40(41)42*43+44,45-46.47/48049150251352453554655756857958:59;60<61=62>63?64@65A66B67C68D69E70F71G72H73I74J75K76L77M78N79O80P81Q82R83S84T85U86V87W88X89Y90Z91[92\93]94^95_96`97a98b99c100d101e102f103g104h105i106j107k108l109m110n111o112p113q114r115s116t117u118v119w120x121y122z123{124|125}126~127DEL
Codes either side
How to read this
- Add 32 to a capital and you get the lowercase letter — one bit flips.
- Digits start at 48, so subtracting 48 from the code gives the number.
- Holding Ctrl clears the top three bits — that is why Ctrl+I is a tab.
- Everything under 32, plus 127, draws nothing. Those show their abbreviation instead.
Frequently asked questions
Q. What is the ASCII code for US?
Decimal 31, hex 1F, octal 037, binary 0011111.
Q. How do I write US in HTML?
As .
Q. How does it go in a URL?
It is encoded as %1F.
Q. How do I type US?
^_.