Editing Chorded keyboard (section)

==Principles of operation==
[[Image:Septambic key numbering.jpg|thumb|An ergonomic chorded keyboard without the board is known as a [[keyer]].]]
Each key is mapped to a number and then can be mapped to a corresponding letter or command. By pressing two or more keys together the user can generate many combinations. In Engelbart's original mapping, he used five keys: 1, 2, 4, 8, 16. The keys were mapped as follows: a = 1, b = 2, c = 3, d = 4, and so on. If the user pressed keys 1 and 2 simultaneously, and then released the keys, 1 and 2 would be added to 3, and since C is the 3rd letter of the alphabet, and the letter "c" appeared. Unlike pressing a chord on a piano, the chord is recognized only after all the keys or mouse buttons are released. Since Engelbart introduced the keyset, several different designs have been developed based on similar concepts.

As a crude example, each finger might control one key which corresponds to one [[bit]] in a [[byte]], so that using seven keys and seven fingers, one could enter any [[character (computing)|character]] in the [[ASCII]] set—if the user could remember the binary codes. Due to the small number of keys required, chording is easily adapted from a desktop to mobile environment.

Practical devices generally use simpler chords for common characters (''e.g.,'' [[Baudot code|Baudot]]), or may have ways to make it easier to remember the chords (''e.g.,'' [[Microwriter]]<ref>{{cite web| year = 2009 | first1 = C | last1 = Rainey | first2 = P | last2 = Rainey | first3 = M | last3 = Rainey |url = http://sites.google.com/site/cykeybellaire/cykey-codecard |title= Bellaire Electronics, Cykey, Microwriter, Agenda |access-date=2011-10-24}}</ref>), but the same principles apply. These portable devices first became popular with the [[wearable computer]] movement in the 1980s.

[[Thad Starner]] from Georgia Institute of Technology and others published numerous studies<ref>{{cite web | url = http://edgarmatias.com/papers/ic93/ | title= Half-QWERTY: A One-handed Keyboard Facilitating Skill Transfer From QWERTY |publisher=Edgar Matias |date=1991-03-21 |access-date=2011-10-24}}</ref><ref>{{cite book| publisher = Computer | date= 2004-10-31 | doi=10.1109/ISWC.2004.19 | pages = 94–101 |hdl=1853/58 |last1 = Lyons|first1 = K.| last2 = Plaisted | first2 = D. | last3 = Starner | first3 = T. | title = Eighth International Symposium on Wearable Computers | chapter = Expert Chording Text Entry on the Twiddler One-Handed Keyboard | isbn = 978-0-7695-2186-2 | citeseerx = 10.1.1.69.3470 | s2cid = 9988843 }}</ref><ref>{{cite book |publisher=Computer | date =2005-10-18 |doi=10.1109/ISWC.2005.49 |pages=170–177 |last1 = Clawson|first1 = J.|last2=Lyons |first2=K. |last3=Starner |first3=T. |last4=Clarkson |first4=E. |title=Ninth IEEE International Symposium on Wearable Computers (ISWC'05) |chapter=The Impacts of Limited Visual Feedback on Mobile Text Entry for the Twiddler and Mini-QWERTY Keyboards |isbn=978-0-7695-2419-1 |citeseerx=10.1.1.119.1185 |s2cid=2072795 }}</ref> showing that two-handed chorded text entry was faster and yielded fewer errors than on a [[QWERTY]] keyboard. Currently [[stenotype]] machines hold the record for fastest word entry.  Many stenotype users can reach 300 words per minute. However, stenographers typically train for three years before reaching professional levels of speed and accuracy.