1
SOH
0x01 · 0000001
ASCII 1 — the SOH character
Not a visible character
SOH is control code 1, hex 01. You type it as ^A, and it draws nothing on screen.
Characters that draw nothing and instead tell the device to do something.
What this control code did
Start of heading
Transmission · Codes that marked where a message began and ended, and whether it arrived.
Seven bits
ASCII is seven bits wide, which is why there are 128 of them. The eighth bit was long left for parity.
0000001
One bit — the sixth, worth 32 — separates the cases. Off gives a capital, on gives a lowercase letter.
- Kind
- Control
- Decimal
- 1
- Hexadecimal
- 0x01
- Octal
- 001
- Binary
- 0000001
- HTML entity
- 
- URL encoding
- %01
- CSS escape
- \1
- Ctrl key
- ^A
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 SOH?
Decimal 1, hex 01, octal 001, binary 0000001.
Q. How do I write SOH in HTML?
As .
Q. How does it go in a URL?
It is encoded as %01.
Q. How do I type SOH?
^A.