A keyboard prototype offers one-handed operation, small size, low
cost of manufacture, and permits the touch typing of large alphabets.
Nathaniel Rochester
IBM Corporation and MIT
Frank C. Bequaert
IBM Corporation
Elmer M. Sharp
IBM Corporation
The chord keyboard is a miniature keyboard that
is operated with one hand and is suitable for typing
large amounts of data at high speed. It can handle a
much larger alphabet than any reasonably sized conventional keyboard. Because it requires only one
hand, it makes new computer applications possible.
Because it is so small and mechanically simple, it
costs less to manufacture than a conventional
keyboard.
depress either one thumb key or two adjacent
thumb keys as a part of a chord. Since there are
seven troughs and since not pressing a trough is a
valid action when forming a chord, there are eight
thumb positions. The commonest character in the
English language is the space, so it is given special
treatment. If the-SPACE trough is pressed as a part
of a chord, a space is inserted ahead of the string of
characters specified by the finger dimples. Thus, it
is possible to type " the" as a single chord. The
thumb can also be used to reverse the normal left-toright sequence of letters in a chord, with or without
Keyboard layout and operation
a space. Thus " and" and "ing" can be typed as
The right-handed chord keyboard is shown in single chords using the SPACE-REVERSE and REFigures 1 and 2. It has a five-by-two array of square VERSE troughs. By using the UPPER trough it is
keys operated by the fingers and a row of four rec- possible to type "THE", and by using the SPACEtangular keys operated by the thumb. The finger UPPER-LOW trough, it is possible to type " The",
keys have rounded depressions, called "dimples." as single chords. There are also troughs for a
When a finger presses a dimple, the corresponding SPECIAL character case and for a NUMBER case.
character is formed. If the "D" dimple is pressed, There is also the equivalent of the case lock of a conone key goes down and a "D" is typed. If the "E" ventional typewriter, which permits the keyboard to
dimple is pressed, two keys go down and a "B" is be locked in a particular case. A detailed description
typed. If the "W"' dimple is pressed, four keys go of the full architecture of the chord keyboard is
down and a "W" is typed. There are 27 dimples on available.'
the keyboard, providing space for the entire
alphabet.
Chords. Using the keyboard and the conventions
The operator may press up to three finger dimples described above, one would type a typical sentence
at once, producing a string of letters in one as follows:
stroke-hence the term "chord," since this is
lI/n/ thius! se/g/ime/nt/ off te/xt/ the/ cho/rd/
analogous to playing a chord on the piano. Typical
bo/und/ar/i/es/ ha/ve/ be/en/ s/ho/wn/ by! li/ne/s/.
examples of chords are "the" and "fro," which are
common strings in English. Since the ring finger A simulation program was used to segment large
and little finger do not function well independently, samples of text in this manner. It was found that
only three fingers are used to form chords. Finger this keyboard allows about 2.2 characters per chord
assignment for chord formation is shown in Figure on average English text. The fact that a person pro2.
duces several characters for each chord makes it
The thumb keyboard has troughs instead of possible to type rapidly on the chord keyboard. In
dimples, and by pressing a trough it is possible to the design of the keyboard, the letters were laid out
December 1978
0018-9162/78/1200-0057$00.75
( 1978 IEEE
57
Chords available for typing text
2750
Chords useful in typing special characters
79
Chords useful in typing numbers
299
Chords reserved for abbreviations,
controls, etc.
544
Unused number and special720
character chords
Thumb controls
15
Total chords possible
4407
This total of 4407 represents the number of unique
key combinations that can be made with the chord
keyboard. It contrasts with the 94 unique combinations possible on a conventional keyboard.
The "reserved" chords rarely or never occur in
English. They provide a very large number of
chords that are available to be used for controls,
editing commands, program functions, and abbreviations. This set of chords makes the keyboard
suitable for use as a computer terminal on which all
functions can be accessed while touch typing, as
contrasted with many conventional terminal
keyboards, on which special function switches cannot be typed by touch.
In using these reserved chords for abbreviations,
a common or awkward word or phrase can be typed
with a single chord. Some abbreviations are language specific. In English, for example, the word
"you" should be abbreviated from three chords to
one. The design of the chord keyboard provides
some built-in chords of this sort and allows the user
to define others. A user noting a repeated word or
.W7.
Figure 1. The chord keyboard. Keys contain dimples, placed so that
one, two, or four keys are depressed, depending on which dimple is
touched. Plate containing thumbkey controls can be moved to the
right side of the keyboard for left-handed users.
on the dimples to optimize the average number of
characters produced per chord for English text.
The design of the chord keyboard permits a very
large number of unique chords to be formed. An
analysis of these possible chords gives the following
breakdown by different chord types:
Figure 2. Full-size
layout of the chord
keyboard. The chord
"the", one of the most
common in English, is
formed by pressing
dimples that depress
both keys in the first,
third, and fifth columns.
DIMPLES PRESSED WITH
I
INDEX
FINGER
1F
I
MIDDLE
FINGER
I
TS
I
RING
FINGER
I
I
I
N
P,-V
0:
CD
<~~~~
Lu
=
LJ
m
~
~~~~i)
UJ cc
CL)
58
58
=:
L
g
-
<
J
L
L)
/
:U
COMPUTER~~~~~~~~;
CL C
I(X
COMPUTER
phrase that is frequently used or difficult to type
can establish that word or phrase as a defined chord
the first time he types it. Subsequently, he can produce the word or phrase with a single chord.
While the layout of the alphabet on the chord keyboard,has been optimized for English, tests indicate
that the' average number of characters produced per
chord is almost as high for other languages. Moreover, the efficiency of chording can be further enhanced for a specific language by defining single
chords to represent the commonest strings of letters
that otherwise could not be typed as single chords.
Special characters. The special characters
available on the keyboard are shown with the letters
in Figure 3. A special character is produced when
the SPECIAL thumb trough is pressed together with
a finger dimple. The special characters have been
laid out on the keyboard to provide a mnemonic
association between the alphabet and the characters. Thus "." (period) is on the same dimple as
"p", .," (comma) is on the "C" dimple, and so on.
This layout makes it easy to learn the positions of
the special characters on the keyboard once the positions of the letters have been learned.
Numbers. The layout of the numbers on the
keyboard is shown in Figure 4. Special characters
I
INDEX
FINGER
used frequently when typing numeric data are also
included on the number keyboard. The number keyboard is designed to permit the typing of single
numbers or chords that will produce two or more
numbers (or numbers and special characters) for
each keystroke. Single numbers or number chords
are produced when one or more finger dimples are
pressed together with the NUMBER thumb trough.
Table 1 shows the chords that can be made using
the number keyboard.
Size of keyboard. The design described above has
drastically reduced keyboard size while greatly expanding the number of available functions. This
reduction has been achieved by cutting down the
physical number of keys and by using the dimples
spanning two and four keys in addition to individual
keys. This has a distinct advantage over the miniature buttons used on hand calculators, since such
buttons produce too great a pressure on the skin to
permit them to be used in continuous, high-speed
data entry. The design of the dimples provides a
comfortable feel for the fingers while minimizing the
number of erroneous key depressions caused by incorrect finger positioning. Figure 5 gives the dimensions of the
keyboard.
I
Table 1.
The number keyboard.
I
MIDDLE FINGER UP (THE CHORD IS WHAT SHOWS ON THE ENGRAVED KEYTOPS.)
INDEX FINGER POSITIONS
UP
Cl)
UP
D
u2
'-'
Figure 3. Layout of special characters on the chord
keyboard. User presses both the dimple carrying the
special character and the SPECIAL trough on the thumb
keyboard.
INDEX
FINGER
I
I
I
MIDDLE
FINGER
I
I
RING
FINGER
*
1
.1
.2
2
- .1
-.2
3
-1
-2
4
.00
.001
.002
5
-.00
- .001
-.002
7
6
000
0001
0002
8
+
,1
+1
+2
,2
9
$
$1
$2
cs-
MIDDLE FINGER ON 00 (THE LEFT 9 DIMPLES REPLICATE THE RIGHT 9.)
INDEX FINGER POSITIONS
CD)
I
1
E2
2
ETC.
1
CD
UP
UP 00
1
01
2
02
ETC.
1
10
11
12
2
20
21
22
3
30
31
32
4
40
41
42
5
50
51
52
6
60
61
62
7
70
71
72
8
80
81
82
9
90
91
92,
MVIDDLE FINGER ON 0 KEY (A 0 IS INSERTED IN THE CHORD PRODUCED.)
INDEX FINGER POSITIONS
Figure 4. Layout of numbers on the chord keyboard.
Mid~
cZ
UP
UP 0
1
001
2
002
ETC.
1
2
3
.0 -.0 -0
.01 -.01 -01
.02 - .02 - 02
4
5
6
7 8
9
.000 -.000 0000 +0 ,0 $0
.0001 -.0001 00001 + 01 ,01 $01
.0002 - .0002 00002 + 02 02 $02
dIe finger controls interpretation of numbe'r chords. With-
middle finger up, chord is what is engraved on the keys.
With middle finger on 00, index-finger dimples mirror
those for ring finger. Middle finger on 0 inserts 0 in chord
produded by index and ring fingers-e.g., pressing - .00
with index finger and 1 with ring finger produces
-.0001.
December 1978
This table indicates the chords that can be made with the number keyboard shown in
Figu Ire 4. The chords are arranged in three arrays, one for each possible position of
thermiddle finger, which controls the interpretation of the chord. In each array there
is a column for each index finger position (in the air or on any one of nine finger positions), and a row for each ring finger position. The position numbers for the index
fing4er duplicate the keyboard layout of numbers for the ring finger.
59
5/16"-
Note: Each surface is a part of
a plane or of a cylinder or sphere
with radius of curvature 1/4".
a) Overall dimensions of the dimples and troughs.
R121"
h_
-4-518"_-N
0 518"
I
I3II/32'"
g2
0 g
518"_-4 518"_ l-W-* 518"_
_
1W3/32"
g
o3/32"
-o.
g
2
1
;
3~~~~~~~~~~~2/2 "
2-25/32"
5/32";
40-3/8"
Note: The four thumb keys
are 3/8" lower than the ten
finger keys.
+
3/32'
3/32" s
- 1~5/8"1
15!8"-1 15/8"_1
3/32"I
5/8";
b) Assembly dimensions of the keyboard.
Figure 5. Overall dimensions of the chord keyboard, shown full size. Each dimple and trough is part of a sphere or
cylinder having a radius of curvature of 1/4 of an inch. The four thumb keys are 3/8 of an inch lower than the ten finger
keys. Scale for figure is actual size.
60
COM PUTEPs
Experimental implementations
The initial model of the chord keyboard was implemented by modifying a Stenotype keyboard. An
IBM Model 1130 computer was modified to accept
input from the keyboard and to drive special
peripheral devices, including a three-line CRT
display and a telephone-line interface. Support software was written for the 1130 computer to generate
the correct characters for keyboard key depressions,
to display these characters, and to provide communication over the telephone-line interface. A
number of application programs were developed to
permit the use of the keyboard as a computer terminal, to provide rudimentary editing and file
manipulation, and to automate the teaching of
touch typing on the keyboard. The keyboard and
the system were in use for over two years.
A second experimental keyboard has been completed. It provides a keyboard that is plug compatible with the standard keyboard of the IBM Type
3277 display station. This unit utilizes standard
keyboard switches and a microprocessor to
duplicate all of the functions of the 78-key 3277
keyboard. This model of the keyboard also provides
a simple-to-use, user-defined chord facility whereby
the user can define single chords to produce strings
of characters as output.
A patent2 has been issued on a hardware embodiment of the chord keyboard.
Typing with the chord keyboard
The typing speed for an experienced typist using
the chord keyboard can be estimated by observing
the performance of skilled stenotypists. The action
required of the right hand in stenotyping is quite
similar to that required in chord-keyboard typing. A
good stenotypist can type three chords per second.
If it is assumed that a chord-keyboard typist can
type at that rate, and using the previously discussed factor of 2.2 characters per chord, a chordkeyboard typist should be able to reach a speed of
79 gross words per minute. Here it is assumed that a
word consists of five characters including spaces.
Use of defined chords for common words and
phrases would further increase typing speed. A
simulation has indicated that the use of defined
chords for six of the more common English words
and syllables would increase typing speed by 10 percent.
There are as yet no expert chord-keyboard typists.
A number of students have learned to type at a
gross typing speed of over 40 words per minute with
low error rates. The initial experience of three
programmer-engineers using the chord keyboard
connected to a 3277 display station to access the
VM/370 system indicates that the user-definedchord facility is extremely valuable to an on-line
computer user and speeds up his work significantly.
December 1978
Learning to type. One can type either visually
(hunt and peck) or by touch on the chord keyboard.
The keys are labeled for visual typing. A visual typing manual is provided with the keyboard. This
manual contains a short initial section that
describes everything a typist needs to know in order
to type anything that can be typed on the keyboard.
After spending about an hour reading this information and trying out the keyboard, a person is able to
use the complete keyboard facilities visually. An additional section of the manual explains details of the
operation of the keyboard for the user interested in
increased proficiency.
An automated system has been developed on the
1130 system for teaching people to touch-type on
the chord keyboard. With this system, material is
displayed on a screen for the student to copy. The
text typed by the student is also displayed on the
screen, together with an indication of the errors he
has made. The lessons are given in three stages. Initially, the user is instructed in the basics of keying
and chord formation while he learns the chord
alphabet. He is then given instruction in capitaliza-
tion, punctuation, and other special characters.
Finally, he is given drills on text to improve his
basic typing speed. This system provides prompting cursors that indicate the chords a student
should be typing and the rate at which he should be
typing a line. Immediately after a line is typed, the
teaching system displays the speed at which the line
was typed.
Two sets of students have been given training in
typing on the chord keyboard using this system.
The initial training sessions yielded little firm
evidence of the speeds of chord keyboard typing
that might typically be reached. It did yield a large
amount of data on how one should touch-type on the
chord keyboard and how this typing should be
taught.
A second class ran from September 1976 through
May 1977, with each student using the system for
four to five hours a week. Of the four students in the
class, three reached gross typing speeds of more
than 40 words per minute; the fourth reached a
speed of approximately 25 words per minute. These
typing speeds were achieved when the students
were typing new material with no more than two errors per minute. If the time spent learning to type
for these students is compared with the time spent
by high school students learning to touch-type on a
conventional keyboard, the learning rates of our
students are generally above the average of the high
school students. It should be noted, however, that a
very powerful automated teaching system was used
to teach the chord keyboard, and all of our students
were of above average intelligence and highly
motivated to.learn. Thus the evidence so far indicates that for typing speeds of up to 40 words per
minute, learning times on the chord keyboard and
on a conventional keyboard are the same. A full
report of this teaching experiment is available.3
Right-hand or left-hand typing. The current protouser to type with
type of the keyboard permits the
61
either the right or the left hand. The thumb keys are
mounted on an adjustable holder that can be positioned either to the right or to the left of the finger
keys and then locked in place. The thumb keys may
also be adjusted so they a,re positioned at an angle
to the finger keys, so they fall more under the natural position of the thumb when the fingers are positioned on the finger keys. The left-hand keyboard is
a mirror-reversed image of the right-hand keyboard.
One student who had learned to type on the righthand keyboard was retrained to type on the lefthand keyboard. This student reached close to his
right-hand typing speed in less than one third the
time he spent learning right-handed typing. An interesting possibility for future work will be to train
someone to type using two keyboards-one with
each hand. It is possible that such a typist might,
with suitable training, be able to reach typing
speeds of upwards of 150 words per minute, thus being able to transcribe speech as fast as a person normally talks.
therefore may find application in devices in areas
such as the home computer market, where the cost
of mechanical hardware must be kept to a minimum.
Handling large alphabets. In certain applications-such as systems for typing Japanese or
Arabic-large, ungainly keyboards have been constructed. The chord keyboard could be used to permit the touch-typing of all symbols in systems requiring large alphabets. Current computer terminal
keyboards have large alphabets, typically including
30 keys that cannot be reached while touch typing.
Adding even more functions to such keyboards
could turn them into unwieldly monsters. The chord
keyboard, on the other hand, can easily handle enormous extension of function.
Handicapped people. One-handed people can use
the chord keyboard to compensate for this disability. Blind people could read braille with one hand and
type with the other. Mute people might use the keyboard as an input device to a speech-synthesis
device.
Applications
The chord keyboard offers advantages over a conventional keyboard in its one-handed operation, its
small size, its low cost, and its facility for touchtyping large alphabets. The chord keyboard should
supplant conventional keyboards in cases where one
or more of these advantages makes it a sufficiently
better choice.
One-handed operation. There are a number of applications in which a person communicating with a
computer requires a hand free to perform other
operations. An operator of a machine or measuring
instrument may wish to communicate instructions
to a computer system while keeping one hand on the
machine controls. A user may wish to use a CRT
display light pen, turn the pages of a book, or leaf
through papers while entering data into the computer. The operator of a vehicle would be able to use
the chord keyboard for data entry while controlling
the vehicle with the other hand.
Small size. The keyboard's small size makes possible a portable, battery-operated microtypewriter
containing the keyboard, associated electronics, and
a small display. Such a device would fit easily in a
briefcase and permit the user to take notes during
lectures or while traveling. The microtypewriter
could also be equipped to function as a microterminal for remote communication with a central computer.
Low cost. Since the chord keyboard has only 14
keys, it should require roughly one third of the
mechanical parts of a conventional keyboard. With
the cost of electronics plummeting, the chord
keyboard should be significantly less expensive to
manufacture than a conventional keyboard. It
62
Prior work
The Stenotype machine,4 stenotyping schools,
and the stenotyping profession serve courts and
governmental bodies by recording proceedings in
mechanical shorthand. The shorthand is later transcribed, usually by the person who recorded it, on a
typewriter. The Stenotype's chord keyboard served
as a model for some mechanical aspects of our chord
keyboard.
Prior to our development work on the chord keyboard, which began in August 1973, it had been
established by experiments that a chord keyboard
usable for the rapid typing of text was technically
feasible, but no practical design had been evolved.
E. T. Klemmer, under the direction of one of the
authors, investigated a chord keyboard intended to
serve as a typewriter keyboard. While this work did
not lead to a practical product, the publication5
stimulated other research, which was summarized
by R. Seibel,6 whose chapter of a book provides
references to and a summary of this and other work
on chord keyboards. This line of research concluded
with the work of a number of experimental psychologists, who noted that the chord keyboard was a
very promising device. D. C. Engelbart developed a
successful rudimentary one-hand chord keyboard7
as part of a terminal; his objective was to make one
hand free to operate a cursor that performs the function of the light pen discussed above. The US Post
Office also developed and tested a rudimentary
10-key keyboard as a part of a system for controlling the flow of mail.6
Our design, therefore, continues and expands this
work and provides a working prototype. The chord
keyboard's unique capabilities and features encourage the exploration of its use as a computer input device. *
COMPUTER
Acknowledgments
w,Frank
The authors wish to acknowledge the substantial
contributions of the 12 MIT students who participated at various times in the chord keyboard
development work and without whose help the work
would not yet have been completed. In particular,
we wish to recognize the significant technical contributions made to the project by Roger J. Bamford
and James W. Leth.
C.
Bequaert
is
staff member
a
with the IBM Cambridge
Scientific
Center. He has worked on the development of the chord keyboard and the
design of computer-based systems for
teaching typing. From 1959 to 1966
he was with the Mitre Corporation. He
holds an AB from Harvard College and
an
MS in electrical
S Stanford University.
engineering
from
Elmer M. Sharp is with the System
Products Division of IBM Corp. in
Poughkeepsie,
References
1. N. Rochester, F. C. Bequaert, and E. M. Sharp, Chord
2.
3.
4.
5.
6.
7.
Keyboard Architecture, IBM Poughkeepsie
Laboratory Tech. Report, to be issued. (Available from
the authors at IBM Cambridge Scientific Center, 545
Technology Square, Cambridge, MA 02139.)
F. C. Bequaert and N. Rochester, "One-Handed
Keyboard and Its Control Means," US Patent
4,042,777, issued Aug. 16, 1977.
F. C. Bequaert and N. Rochester, Teaching Typing on
a Chord Keyboard, IBM Poughkeepsie Laboratory
Tech. Report TR 00.2918, Dec. 26, 1977. (Available
from the authors; see reference 1.)
H. H. Hill, Machine Touch Shorthand Theory, Touch
Shorthand Academy, Inc., Boston, 1959.
G. R. Lockhead and E. T. Klemmer, An Evaluation of
an 8-Key Word-Writing Typewnrter, IBM Research
Report RC-180, IBM Research Center, Yorktown
Heights, New York, Nov. 1959.
R. Seibel, "Data Entry Devices and Procedures," in
Human Engineering Guide to Equipment Design, H.
P. Van Cott and R. G. Kinkade, eds., McGraw-Hill,
1963. (Also available from US Government Printing
Office.)
D. C. Engelbart and W. K. English, "A Research
Center for Augmenting Human Intellect," AFIPS
Conf. Proc., Vol. 33, 1968 FJCC, pp. 395-410.
A Nathaniel Rochester is
an IBM
Fellow of the IEEE, and at
present visiting scientist at MIT. He
was responsible for the architecture of
Fellow,
a
a
IBM's first
general-purpose electronic
computer, the 701, and wrote the first
assembly program (IRE Trans. Electronic
Computers,
March
1953).
He
has served on many IRE, IEEE, and
AFIPS committees, published 16
papers, and holds 20 US patents. His interests are computer architecture, programming, and the man-machine
interface.
December 1978
N.Y.
He
is
a
senior
engineer on Mr. Rochester's staff and
has most recently concentrated on the
application of microprocessors to complex control situations. His previous
work with IBM has included advanced
systems design, timesharing system
design,
graphic
I/O
devices,
and,
special systems work on large-scale, real-time applications. Prior to joining IBM, he worked for the National
Advisory Committee for Aeronautics (now NASA) on
automatic data recording and analysis.
Sharp received AB and MS degrees in physics from Cornell University.
Computers in Critical Care
and Pulmonary Medicine
announce
AN
INTERNATIONAL
SYMPOSIUM
May 24-26, 1979
at
Norwalk Hospital
Yale University School of Medicine
Norwalk Hospital, Connecticut 06856
The purpose of this meeting is to bring together computer
specialists, biomedical engineers, and physicans who are interested in the application of computer technology to the
diagnosis and treatment of critically ill patients.
The program will consist of one day devoted to respiratory
monitoring and the other two days will be devoted to the presentation of papers pertaining to the application of computer
technology to the monitoring of critically ill patients.
Invited presentations by internationally known specialists will
be the keynote of each session, abstracts for other presentations
are requested by February 15, 1979.
Enrollment will be limited to 175 persons. Registration fee will
be $150.00. For further information write to:
Sreedhar Nair, M.D., F.A.C.P.,
Symposium Chairman
Computers in Critical Care & Pulmonary Medicine
Norwalk Hospital
Yale University School of Medicine
Norwalk, Connecticut 06856
63