The Top Key

By Xah Lee. Date: . Last updated: .

The Top key first appeared on SAIL Keyboard around 1970.

SAIL keyboard b1c80-s306x204
SAIL Keyboard

It is like the Shift key, used to input Math Symbols ∞ .

Then it appeared on Lisp keyboards

lisp knight keyboard-s339x184
Knight Keyboard
Space Cadet

Seems, after the Space Cadet, the Top key disappeared. But the concept is picked up, as Apple's ⌥ option key [see Mac Keyboard Viewer] and AltGraph key. [see Alt Graph Key, Compose Key, Dead Key]

Xah Keyboard Guide