View source for Space-cadet keyboard

{{Short description|Keyboard used on MIT Lisp machines, influential to Emacs}}
[[File:Space-cadet.jpg|thumb|400px|right|The [[Symbolics]]-labeled {{dubious-span|version|reason=Someone should confirm if it was really a different ''version'' – not just a different label on an identical keyboard, or else just make this say "Symbolics-labeled space cadet keyboard"|date=March 2025}} shown here was only used with the LM-2, which was Symbolics' repackaged version of the [[Lisp machine|MIT CADR]]. Later Symbolics systems used a greatly simplified keyboard, the [[Symbolics#Symbolics keyboard|Symbolics keyboard]], that retained only the basic layout and the more commonly used function and [[modifier key]]s from the space-cadet keyboard.<ref>{{Cite web
| title=Space-cadet Keyboard and Lisp Machine Keyboards
| author=Xah Lee
| date=2011-10-27
| url=http://xahlee.info/kbd/lisp_keyboards.html}}</ref>]]

The '''space-cadet keyboard''' is a keyboard designed by John L. Kulp in 1978 and used on [[Lisp machine]]s at [[Massachusetts Institute of Technology]] (MIT),<ref>{{Cite web| title=some ideas about the keyboard design for the LISP machine | format=TXT | url=https://raw.githubusercontent.com/mietek/mit-cadr-system-software/master/src/lmdoc/kbdpro.3 | archive-url=https://web.archive.org/web/20190228004001/https://raw.githubusercontent.com/mietek/mit-cadr-system-software/master/src/lmdoc/kbdpro.3 | archive-date=2019-02-28}}</ref><ref>{{Cite web | url=https://people.csail.mit.edu/gregs/ll1-discuss-archive-html/msg02212.html |title = Re: Pretty-lambdas}}</ref><ref>{{Cite web | url=https://news.ycombinator.com/item?id=2191014 |title = I know this is another "neckbeard" comment (Love that term), but anyone who ever... &#124; Hacker News}}</ref> which inspired several still-current jargon terms{{Citation needed|date=April 2022}} in the field of [[computer science]] and influenced the design of [[Emacs]]. It was inspired by the [[Knight keyboard]], which was developed for the Knight TV system, used with MIT's [[Incompatible Timesharing System]].

== Description ==
The space-cadet keyboard was equipped with seven [[modifier key]]s: four keys for [[bucky bit]]s ({{Key top|Control|3=true}}, {{Key top|Meta}}, {{Key top|Super}}, and {{Key top|Hyper}}), and three shift keys, called {{Key top|Shift}}, {{Key top|Top}}, and {{Key top|Front}} (which was labeled on the ''front'' of the key; the top of the keycap was labeled {{Key top|Greek}}). {{Key press|Meta}} had been introduced on the earlier Knight keyboard, while {{Key press|Hyper}} and {{Key press|Super}} were introduced by this keyboard.<ref name="jargon file">{{Cite book
| title=The Jargon File
| year=2007
| publisher=Xinware Corporation
| pages=128
| isbn=978-1-897454-66-4
}}</ref> Each group was in a row, thus allowing easy [[Chorded keyboard|chording]], or pressing of several modifier keys; for example, {{Key press|Control|Meta|Hyper|Super}} could be pressed with the fingers of one hand, while the other hand pressed another key.

Many keys had three symbols on them, accessible by means of the shift keys: a letter and a symbol on the top, and a Greek letter on the front. For example, the {{Key top|G}} key had a "G" and an [[Arrow (symbol)|up-arrow]] ("↑") on the top, and the Greek letter [[gamma]] ("{{serif|γ}}") on the front. By pressing this key with one hand while playing an appropriate "chord" with the other hand on the shift keys, the user could get the following results:

{| class="wikitable"
!Key pressed
!Result
|-
| {{Key press|G}}
| <kbd>g</kbd> (lowercase G)
|-
| {{Key press|Shift|G}}
| <kbd>G</kbd> (uppercase G)
|-
| {{Key press|Front|G}}
| <kbd>γ</kbd> (lowercase [[gamma]])
|-
| {{Key press|Front|Shift|G}}
| <kbd>Γ</kbd> (uppercase gamma)
|-
| {{Key press|Top|G}}
| <kbd>↑</kbd> (upwards arrow)
|}

Each of these might, in addition, be typed with any combination of the {{Key top|Control|3=true}}, {{Key top|Meta}}, {{Key top|Super}}, and {{Key top|Hyper}} keys. By combining the modifier keys, it is possible to make {{nowrap|(50 keys &times; 5 shift types) &times; 2{{sup|4 bucky keys}} {{=}} 4000 different inputs.}} This allowed the user to type very complicated mathematical text, and also to have thousands of single-character commands at their disposal. Many users were willing to memorise the command meanings of so many characters if it reduced typing time. This attitude shaped the interface of [[Emacs]].<ref name="isbn1-56592-152-6">{{Cite book|last1=Cameron|first=Debra|chapter-url=https://archive.org/stream/learninggnuemacs00came#page/408/mode/2up|title=Learning GNU Emacs|last2=Rosenblatt|first2=Bill|last3=Raymond|first3=Eric|publisher=O'Reilly|year=1996|isbn=1-56592-152-6|editor-last=Loukides|editor-first=Mike|edition=Second|location=Sebastopol, CA|pages=408–409|chapter=Emacs and X|author-link3=Eric S. Raymond|chapter-url-access=registration}}</ref>{{efn|The way the space-cadet keyboard influenced the design and usage conventions of the Emacs text editor compares with the influence the [[ADM-3A]] terminal's keyboard—notably its {{Key top|Esc}} key feature—had upon the competing [[Vi (text editor)|vi]] text editor.<ref name=xahlee>{{Cite web
| url=http://xahlee.info/kbd/keyboard_hardware_and_key_choices.html
| title=History of Emacs ＆ vi Keys (Keyboard Influence on Keybinding Design)
| author=Xah Lee
}}</ref> In both cases, these were the keyboards used by each editor's respective original developers.}} Other users, however, thought that so many keys were excessive and objected to this design on the grounds that such a keyboard can be difficult to operate.<ref name= "jargon file" />

Emacs uses "M-" as the prefix for {{Key top|Alt}} when describing key presses: the "M-" stood for {{Key press|Meta}} on the space-cadet keyboard, and when Emacs was ported to PCs, the {{Key press|Alt}} key was used in place of {{Key press|Meta}}.

This keyboard included a {{Key top|Macro}} key which had limited application support. It also included four Roman Numeral keys ({{Key press|I}}, {{Key press|II}}, {{Key press|III}}, and {{Key press|IV}}) which allowed for easy interaction with lists of four or fewer choices.<ref name="jargon file" />

== See also ==
* [[Lisp machine]]
* [[Symbolics]]
* [[Knight keyboard]]

== Notes ==
{{notelist}}

== References ==
{{Refbegin}}
{{JargonFile}}
{{Refend}}
{{Reflist}}

== External links ==
* [https://web.archive.org/web/20150112030657/http://home.comcast.net/~mmcm/kbd/SpaceCadet.html Space Cadet]: Mike McMahon's discussion of the keyboard, with illustrative pictures and technical documentation
* [http://www.catb.org/jargon/html/S/space-cadet-keyboard.html Jargon File entry] on the space-cadet keyboard
* [http://deskthority.net/viewtopic.php?f=2&t=98 The Lisp keyboards]: overview of the space-cadet and other famous Lisp keyboards
* {{Cite web
| title=Space-cadet Keyboard and Lisp Machine Keyboards
| author=Xah Lee
| date=2011-10-27
| url=http://xahlee.info/kbd/lisp_keyboards.html}}
{{Keyboard keys}}

[[Category:Computer keyboard types]]
[[Category:Lisp (programming language)]]