What ⎕ means
It introduces evaluated input or an interpreter’s system name.
Alone, it prompts for an expression; before letters, it begins names such as ⎕IO, the setting that determines where array indexing starts.
Kenneth Iverson’s data-processing and teaching notation took shape in the mid-1950s. The quad was included partly because it could be superimposed on other characters to form symbols.
Don't confuse it with
4⌷⌸⌹⌺
APL Functional Symbol Squish Quad
shares “apl”, “functional”, “quad”, “symbol”
APL Functional Symbol Quad Equal
shares “apl”, “functional”, “quad”, “symbol”
APL Functional Symbol Quad Divide
shares “apl”, “functional”, “quad”, “symbol”
APL Functional Symbol Quad Diamond
shares “apl”, “functional”, “quad”, “symbol”
Combination ideas
2Sets the origin used for array indexing.
Displays the value to its right.
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 2395, 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 quad”.
Linux
Ctrl+Shift+UType 2395, then Enter or Space.
HTML
⎕CSS
\2395APL keyboard
Use the quad on your APL layout’s symbol layer; key placement varies by layout.
Other keyboards
Use a Unicode input method; standard QWERTY has no universal key for the quad.
Codes and encoding1 code points
HTML decimal
⎕
HTML hex
⎕
CSS content
content: "\2395";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%8E%95
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.