Space-cadet keyboard
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), which 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. Description. The space-cadet keyboard was equipped with seven modifier keys: four keys for bucky bits (, , , and ), and three shift keys, called , , and (which was labeled on the "front" of the  key; the top was labeled ). had been introduced on the earlier Knight keyboard, while and were introduced by this keyboard. Each group was in a row, thus allowing easy chording, or pressing of several modifier keys; for example, 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 had a "G" and an up-arrow ("↑") 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 could 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 formula_1. 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; compare the use of the key in vi, due to the convenient position of the key on the ADM-3A terminal. 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-" stood for on the space-cadet keyboard, and when Emacs was ported to PCs, the key was used in place of . This keyboard included a key which had limited application support. It also included  four Roman Numeral keys (, , , and ) which allowed for easy interaction with lists of four or fewer choices.