The space-cadet keyboard is a keyboard designed by John L. Kulp in 1978 and used on Lisp machines at Massachusetts Institute of Technology (MIT). It inspired several still-current jargon terms 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.
The space-cadet keyboard is equipped with seven modifier keys: four keys for bucky bits (, , , and ), and three shift keys, called , , and (which is labeled on the front of the key; the top of the keycap is labeled ). had been introduced on the earlier Knight keyboard, while and were introduced by this keyboard. Each group is in a row, thus allowing easy chording, or pressing of several modifier keys; for example, can be pressed with the fingers of one hand, while the other hand presses another key.
Many keys have 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 has a "G" and an up-arrow ("âÂÂ") on the top, and the Greek letter gamma ("") 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 can get the following results:
Each of these might, in addition, be typed with any combination of the , , , and keys. By combining the modifier keys, it is possible to make This allows 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. 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.
Emacs uses "M-" as the prefix for when describing key presses: the "M-" stands for on the space-cadet keyboard, and when Emacs was ported to PCs, the key was used in place of .
This keyboard includes a key which has limited application support. It also includes four roman numeral keys (, , , and ) which allow for easy interaction with lists of four or fewer choices.