What ⍊ means
Two conventions label the tack direction differently. APL calls ⍊ “Up Tack Underbar”; Unicode calls it “Down Tack Underbar.”
Set 68, a 94-character set for exchanging APL workspaces (saved program environments), used the Bosworth convention for tack directions. Unicode later used the London convention for four plain tacks but kept five compound names, including ⍊, in the old orientation. In 2000, the APL Working Group recorded the mismatch and proposed corrections.
Don't confuse it with
4⍎⍌⍑⍕
APL Functional Symbol Down Tack Jot
shares “apl”, “down”, “functional”, “symbol”, “tack”
APL Functional Symbol Quad Down Caret
shares “apl”, “down”, “functional”, “symbol”
APL Functional Symbol Up Tack Overbar
shares “apl”, “functional”, “symbol”, “tack”
APL Functional Symbol Up Tack Jot
shares “apl”, “functional”, “symbol”, “tack”
Questions people ask
1Why does ⍊ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ⍊
Windows (Word)
Alt+XType 234A, then Alt+X to get ⍊.
Windows
Win+Rrun charmap for the full table, or use the emoji picker's Ω symbols tab (Win + .).
macOS
Control+Command+SpaceOpen the character viewer and search “apl functional symbol down tack underbar”.
Linux
Ctrl+Shift+UType 234a, then Enter or Space.
HTML
⍊CSS
\234ACode
Java and Python strings accept the Unicode escape `\u234A`.
APL input
Use the APL system's keyboard layout or language bar; input mappings depend on the implementation.
Codes and encoding1 code points
HTML decimal
⍊
HTML hex
⍊
CSS content
content: "\234A";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%8D%8A
1
On screen
1
Code points
1
JS .length
3
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.