U.S. patent number 3,929,216 [Application Number 05/394,516] was granted by the patent office on 1975-12-30 for input keyboards.
Invention is credited to Harvey Einbinder.
United States Patent |
3,929,216 |
Einbinder |
December 30, 1975 |
Input keyboards
Abstract
Input keyboards are disclosed for typewriters, computer
terminals, and other devices processing alphanumeric information
that maximize entry rates and stroking accuracy, and minimize
finger motions and the time needed to master the keyboard. A
general method is also disclosed of designing such keyboards for
any alphabetic language. The invention places the space key and
four common vowels directly under the fingers of the left hand, and
five common consonants directly under the fingers of the right
hand. Two-finger chord strokes generate common two-character
sequences belonging to the same hand. The keyboards are split into
rotated halves containing curved key rows and slanted key tops of
variable height to follow the architecture of the hand. The
invention includes keyboards for English, German, French, Italian,
Spanish, and Portuguese.
Inventors: |
Einbinder; Harvey (New York,
NY) |
Family
ID: |
23559289 |
Appl.
No.: |
05/394,516 |
Filed: |
September 4, 1973 |
Current U.S.
Class: |
400/484; 400/486;
400/489; 400/109; 400/488; 400/492 |
Current CPC
Class: |
B41J
5/10 (20130101); G06F 3/0219 (20130101) |
Current International
Class: |
B41J
5/10 (20060101); B41J 5/00 (20060101); G06F
3/023 (20060101); B41J 005/10 () |
Field of
Search: |
;197/9,98,99,100 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
808,874 |
|
Feb 1937 |
|
FR |
|
1,255,117 |
|
Nov 1967 |
|
DT |
|
2,017,063 |
|
Oct 1970 |
|
DT |
|
174,678 |
|
Apr 1935 |
|
CH |
|
Other References
"The Tyranny of Qwerty," Charles Lekberg, Sat. Rev., Sept. 30,
1972, pp. 37-40..
|
Primary Examiner: Burr; Edgar S.
Assistant Examiner: Sewell; Paul T.
Claims
I claim:
1. An input keyboard for the transfer of information to a machine
by a human operator, comprising:
a plurality of keys arranged in transversely oriented key rows as
viewed by the operator: the number key row being situated at the
greatest distance from the operator; the upper letter key row being
situated closer to the operator than the number key row; the home
key row being situated closer to the operator than the upper letter
key row; the lower letter key row being situated closer to the
operator than the home key row; and the thumb key row being
situated closer to the operator than the lower letter key row;
wherein the upper letter key row comprises twelve keys: six keys on
the left hand side of the keyboard as viewed by the operator, and
six keys on the right hand side of the keyboard as viewed by the
operator;
wherein the home key row comprises twelve keys: six keys on the
left hand side of the keyboard as viewed by the operator, and six
keys on the right hand side of the keyboard as viewed by the
operator;
wherein the thumb key row comprises six keys: three keys on the
left hand side of the keyboard as viewed by the operator, and three
keys on the right hand side of the keyboard as viewed by the
operator;
wherein the keys on the upper letter key row are designated in
serial order along the upper letter key row as viewed by the
operator from the outer edge of the keyboard from the center of the
keyboard as follows: on the left hand side of the keyboard as
viewed by the operator--the first upper letter key, the second
upper letter key, the third upper letter key, the fourth upper
letter key, the fifth upper letter key, and the sixth upper letter
key, respectively; and on the right hand side of the keyboard as
viewed by the operator--the seventh upper letter key, the eighth
upper letter key, the ninth upper letter key, the tenth upper
letter key, the eleventh upper letter key, and the twelfth upper
letter key, respectively;
wherein the keys on the home key row are designated in serial order
along the home key row as viewed by the operator from the outer
edge of the keyboard to the center of the keyboard as follows: on
the left hand side of the keyboard as viewed by the operator--the
first home key, the second home key, the third home key, the fourth
home key, the fifth home key, and the sixth home key, respectively;
and on the right hand side of the keyboard as viewed by the
operator--the seventh home key, the eighth home key, the ninth home
key, the tenth home key, the eleventh home key, and the twelfth
home key, respectively;
wherein the keys on the thumb key row are designated in serial
order along the thumb key row as viewed by the operator from the
outer edge of the keyboard to the center of the keyboard as
follows: on the left hand side of the keyboard as viewed by the
operator--the first thumb key, the second thumb key, and the third
thumb key, respectively; and on the right hand side of the keyboard
as viewed by the operator--the fourth thumb key, the fifth thumb
key, and the sixth thumb key, respectively;
wherein the upper and lower case forms of a single letter are
assigned to the same key;
wherein space and letter keys are arranged on the left hand side of
the keyboard as viewed by the operator as follows: the space key,
which generates the separation between words, is assigned to the
second thumb key; one high frequency vowel is assigned to the
second home key; a second high frequency vowel is assigned to the
third home key; a third high frequency vowel is assigned to the
fourth home key; and a fourth high frequency vowel is assigned to
the fifth home key; wherein each of these four high frequency
vowels is a different letter; and
wherein letter keys are arranged on the right hand side of the
keyboard as viewed by the operator as follows: one high frequency
consonant is assigned to the fifth thumb key; a second high
frequency consonant is assigned to the eighth home key; a third
high frequency consonant is assigned to the ninth home key; and a
fourth high frequency consonant is assigned to the tenth home key;
and a fifth high frequency consonant is assigned to the eleventh
home key; wherein each of these five high frequency consonants is a
different letter.
2. A keyboard, as in claim 1 for the English language comprising
space and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator:
the space key is assigned to the second thumb key, I is assigned to
the second home key, O is assigned to the third home key, E is
assigned to the fourth home key, and A is assigned to the fifth
home key; and
on the right hand side of the keyboard as viewed by the operator: N
is assigned to the fifth thumb key, R is assigned to the eighth
home key, S is assigned to the ninth home key, T is assigned to the
tenth home key, and H is assigned to the eleventh home key.
3. A keyboard, as in claim 1, for the Italian language comprising
space and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator:
the space key is assigned to the second thumb key, O is assigned to
the second home key, I is assigned to the third home key, A is
assigned to the fourth home key, and E is assigned to the fifth
home key; and
on the right hand side of the keyboard as viewed by the operator: N
is assigned to the fifth thumb key, L is assigned to the eighth
home key, S is assigned to the ninth home key, T is assigned to the
tenth home key, and R is assigned to the eleventh home key.
4. A keyboard, as in claim 1, for the Spanish language comprising
space and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator:
the space key is assigned to the second thumb key, O is assigned to
the second home key, I is assigned to the third home key, A is
assigned to the fourth home key, and E is assigned to the fifth
home key; and
on the right hand side of the keyboard as viewed by the operator: R
is assigned to the fifth thumb key, S assigned to to the eighth
home key, T is assigned to the ninth home key, N is assigned to the
tenth home key, and D is assigned to the eleventh home key.
5. A keyboard, as in claim 1, for the French language comprising
space and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator:
the space key is assigned to the second thumb key, A is assigned to
the second home key, I is assigned to the third home key, E is
assigned to the fourth home key, and U to the fifth home key;
and
on the right hand side of the keyboard as viewed by the operator: N
is assigned to the fifth thumb key, S is assigned to the eighth
home key, T is assigned to the ninth home key, R is assigned to the
tenth home key, and L is assigned to the eleventh home key.
6. A keyboard, as in claim 1, for the German language comprising
space and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator:
the space key is assigned to the second thumb key, A is assigned to
the second home key, U is assigned to the third home key, E is
assigned to the fourth home key, and I is assigned to the fifth
home key; and
on the right hand side of the keyboard as viewed by the operator: N
is assigned to the fifth thumb key, R is assigned to the eighth
home key, S is assigned to the ninth home key, T is assigned to the
tenth home key, and H is assigned to the eleventh home key.
7. A keyboard, as in claim 1, comprising a plurality of keys:
wherein the keys as viewed by the operator are arranged in two
separate groups of keys: one group of keys being situated on the
left hand side of the keyboard; the other group of keys being
situated on the right hand side of the keyboard; with an area in
the center of the keyboard separating these two groups of keys;
wherein the keys on the number key row, the upper letter key row,
and the home key row on each side of the keyboard as viewed by the
operator are arranged in a curved convex arc in each key row; and
these curved convex arcs on each side of the keyboard are parallel
to each other;
wherein the number key row, the upper letter key row, the home key
row, the lower letter key row, and the thumb key row as viewed by
the operator are rotated clockwise on the left hand side of the
keyboard, and are rotated counterclockwise on the right hand side
of the keyboard,
wherein the key tops belonging to the second home key, the third
home key, the fourth home key, the fifth home key, the eighth home
key, the ninth home key, the tenth home key, and the eleventh home
key are each parallel to the base of the machine to which the
keyboard is attached--so that when the machine rests on a
horizontal surface, each of these home key tops is horizontally
oriented;
wherein the heights of the key tops belonging to the second home
key, the third home key, the fourth home key, the the fifth home
key, the eighth home key, the ninth home key, the tenth home key,
and the eleventh home key vary to compensate for differences in
finger length, so that when the height of these key tops are
measured perpendicular to the plane on which the machine attached
to the keyboard rests: the heights of the second home key and the
eighth home key, which are equal, are tallest; the heights of the
fifth home key and the eleventh home key, which are equal, are
shorter than the heights of the second home key and the eighth home
key; the heights of the third home key and the ninth home key,
which are equal, are shorter than the heights of the fifth home key
and the eleventh home key; and the heights of the fourth home key
and the tenth home key, which are equal, are shorter than the
heights of the third home key and the ninth home key;
wherein keys on the number key row, the upper letter key row, and
the home key row are arranged so that when a plane passes through
the center of the second home key, the third home key, the fourth
home key, the fifth home key, the eighth home key, the ninth home
key, the tenth home key, and the eleventh home key,
respectively--and this plane is perpendicular to the transverse arc
that passes through the center of home keys along the home key row
from the outer edge of the keyboard to the center of the keyboard,
this plane passes through the center of a key on the upper letter
key row and through the center of a key on the number key row;
wherein the stroking surface of the first thumb key and the third
thumb key each slope toward the second thumb key, so that the
second thumb key rests in a trough on the left hand thumb row as
viewed by the operator;
wherein the stroking surface of the fourth thumb key and the sixth
thumb key each slope toward the fifth thumb key, so that the fifth
thumb key rests in a trough on the right hand thumb row as viewed
by the operator; and
wherein the stroking surfaces on the number key row, the upper
letter key row, and the lower letter key row slope toward the home
key row, so that when the heights of stroking surfaces are measured
in terms of their perpendicular distance from the base of the
machine to which the keyboard is attached: for individual keys on
the number key row--the edge of the stroking surface that is
farthest from the operator is taller than the edge of the stroking
surface on the same key that is nearest to the operator; for
individual keys on the upper letter key row--the edge of the
stroking surface that is farthest from the operator is taller than
the edge of the stroking surface on the same key that is nearest to
the operator; and for individual keys on the lower letter key
row--the edge of the stroking surface that is nearest to the
operator is taller than the edge of the stroking surface on the
same key that is farthest from the operator.
8. A keyboard, as in claim 2, for the English language comprising
shift and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator: U
assigned to the first thumb key, and shift key assigned to the
fourth upper letter key; and
on the right hand side of the keyboard as viewed by the operator: L
assigned to the fourth thumb key, D assigned to the twelfth home
key, C assigned to the ninth upper letter key, M assigned to the
tenth upper letter key, and F to the eleventh upper letter key.
9. A keyboard, as in claim 3, for the Italian language comprising
shift and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator: U
assigned to the first thumb key, and shift key assigned to the
fourth upper letter key; and
on the right hand side of the keyboard as viewed by the operator--M
assigned to the fourth thumb key, D assigned to the twelfth home
key, P assigned to the ninth upper letter key, C assigned to the
tenth upper letter key, and H assigned to the eleventh upper letter
key.
10. A keyboard, as in claim 4, for the Spanish language comprising
shift and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator: U
assigned to the first thumb key, and shift key assigned to the
fourth upper letter key; and
on the right hand side of the keyboard as viewed by the operator: L
assigned to the fourth thumb key, C assigned to the twelfth home
key, V assigned to the ninth upper letter key, M to the tenth upper
letter key, and P to the eleventh upper letter key.
11. A keyboard, as in claim 5, for the French language comprising
shift and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator: O
assigned to the first thumb key, and shift key assigned to the
fourth upper letter key; and
on the right hand side of the keyboard as viewed by the operator: M
assigned to the fourth thumb key, D assigned to the twelfth home
key, P assigned to the ninth upper letter key, C assigned to the
tenth upper letter key, and H to the eleventh upper letter key.
12. A keyboard, as in claim 6, for the German language comprising
shift and letter keys arranged as follows:
on the left hand side of the keyboard as viewed by the operator: O
assigned to the first thumb key, shift key assigned to the fourth
upper letter key, and (lower case: umlaut: upper case: umlaut)
assigned to the fourth upper letter key; and
on the right hand side of the keyboard as viewed by the operator: L
assigned to the first thumb key, D assigned to the twelfth home
key, G assigned to the ninth upper letter key, C assigned to the
tenth upper letter key, and B assigned to the eleventh upper letter
key.
13. A keyboard, as in claim 8, for the English language comprising
character and control keys arranged in serial order along key rows
as viewed by the operator from the outer edge of the keyboard to
the center of the keyboard as follows:
on the left hand side of the keyboard as viewed by the operator:
along the thumb key row: U assigned to the first thumb key, the
space assigned to the second thumb key, and the carriage return
assigned to the third thumb key; along the home key row: Y assigned
to the first home key, I assigned to the second home key, O
assigned to the third home key; E assigned to the fourth home key,
A assigned to the fifth home key, and (lower case: comma; upper
case: comma) assigned to the sixth home key; along the upper letter
key row: (lower case: colon: upper case: open parenthesis) assigned
to the first upper letter key, (lower case: question mark; upper
case; semi-colon) assigned to the second upper letter key, X
assigned to the third upper letter key, the shift assigned to the
fourth upper letter key, (lower case: period; upper case: period)
assigned to the fifth upper letter key, and (lower case: hyphen;
upper case: underline) assigned to the sixth upper letter key; on
the lower letter key row: J assigned to the first lower letter key
situated between the second home key and the operator, Z assigned
to the second lower letter key situated between the fifth home key
and the operator, and (lower case: apostrophe, upper case:
exclamation point) assigned to the third lower letter key situated
between the sixth home key and the operator; and on thumb keys: the
shift lock assigned to the thumb key situated between the second
thumb key and the operator, and the margin release assigned to the
thumb key situated at the inner end of the lower letter key row in
the center of the keyboard as viewed by the operator;
on the right hand side of the keyboard as viewed by the operator:
along the thumb key row: L assigned to the fourth thumb key, N
assigned to the fifth thumb key, and W assigned to the sixth thumb
key; along the home key row: G assigned to the seventh home key, R
assigned to the eighth home key; S assigned to the ninth home key;
T assigned to the tenth home key, H assigned to the eleventh home
key, and D assigned to the twelfth home key; along the upper letter
key row: (lower case: double quotation marks; upper case: close
parenthesis) assigned to the seventh upper letter key, B assigned
to the eighth upper letter key, C assigned to the ninth upper
letter key, M assigned to the tenth upper letter key, F assigned to
the eleventh upper letter key, and K assigned to the twelfth upper
letter key: along the lower letter row: V assigned to the fourth
lower letter key situated between the eighth home key and the
operator, P assigned to the fifth lower letter key situated between
the eleventh home key and the operator, and Q assigned to the sixth
lower letter key situated between the twelfth home key and the
operator; and on thumb keys: the backspace assigned to the thumb
key situated on between the fifth thumb key and the operator, and
the tabulator assigned to the thumb key situated at the inner end
of the lower letter key row in the center of the keyboard as viewed
by the operator.
14. A keyboard, as in claim 9, for the Italian language comprising
character and control keys arranged in serial order along key rows
as viewed by the operator from the outer edge of the keyboard to
the center of the keyboard as follows:
on the left hand side of the keyboard as viewed by the operator:
along the thumb key row: U assigned to the first thumb key, space
assigned to the second thumb key, and carriage return assigned to
the third thumb key; along the home key row: (lower case: accent
acute; upper case: accent acute) assigned to the first home key, O
assigned to the second home key, I assigned to the third home key,
A assigned to the fourth home key, and E assigned to the fifth home
key; and (lower case: apostrophe) assigned to the sixth home key;
along the upper letter key row: (upper case: accent grave; lower
case; accent grave) assigned to the third upper letter key, the
shift assigned to the fourth upper letter key, and (lower case:
hyphen; upper case: underline) assigned to the fifth upper letter
key; and on thumb keys: the shift lock assigned to the thumb key
situated between the second thumb key and the operator, and the
margin release situated on the thumb key at the inner end of the
lower letter key row in the center of the keyboard as viewed by the
operator; and
on the right hand side of the keyboard as viewed by the operator:
along the thumb key row: M assigned to the fourth thumb key, N
assigned to the fifth thumb key, and F assigned to the sixth thumb
key; on the home key row: B assigned to the seventh home key, L
assigned to the eighth home key, S assigned to the ninth home key,
T assigned to the tenth home key, R assigned to the eleventh home
key; and D assigned to the twelfth home key; on the upper letter
key row: (lower case: period; upper case; period) assigned to the
seventh upper letter key; V assigned to the eighth upper letter
key, P assigned to the ninth upper letter key, C assigned to the
tenth upper letter key, H assigned to the eleventh upper letter
key, and (lower case: comma; upper case: comma) assigned to the
twelfth upper letter key; and on the lower letter row: Z assigned
to the lower letter key situated between the eighth home key and
the operator, (lower case: colon; upper case: exclamation point)
assigned to the lower letter key situated between the ninth home
key and the operator; (lower case: question mark; upper case:
semi-colon) situated between the tenth home key and the operator, G
assigned to the lower letter key situated between the eleventh home
key and the operator, and Q situated between the twelfth home key
and the operator; and on thumb keys: the backspace assigned to the
thumb key situated between the fifth thumb key and the operator,
and the tabulator assigned to the thumb key situated at the inner
end of the lower letter key row in the center of the keyboard as
viewed by the operator.
15. A keyboard, as in claim 10, for the Spanish language comprising
character and control keys arranged in serial order along key rows
as viewed by the operator from the outer edge of the keyboard to
the center of the keyboard as follows:
on the left hand side of the keyboard as viewed by the operator:
along the thumb key row: U assigned to the first thumb key, the
space assigned to the second thumb key, and the carriage return
assigned to the third thumb key; along the home key row: (lower
case: hyphen; upper case: underline) assigned to the first home
key, O assigned to the second home key, I assigned to the third
home key, A assigned to the fourth home key, E assigned to the
fifth home key, and (lower case: comma; upper case; comma) assigned
to the sixth home key; along the upper letter key row: X assigned
to the second upper letter key, (lower case: question mark; upper
case: inverted question mark) assigned to the third upper letter
key, the shift assigned to the fourth upper letter key, (upper
case: period; lower case: period) assigned to the fifth upper
letter key, and (lower case: exclamation point; upper case:
inverted exclamation point) assigned to the sixth upper letter key;
along the lower letter row: (lower case: accent acute; upper case:
accent acute) assigned to the lower letter key situated between
fifth home key and the operator; and on thumb keys: the shift lock
assigned to the thumb key situated between the second thumb key and
the operator, and the margin release situated at the inner end of
the lower letter key row in the center of the keyboard as viewed by
the operator; and
on the right hand side of the keyboard as viewed by the operator:
along the thumb key row: L assigned to the fourth thumb key row, R
assigned to the fifth thumb key, and H assigned to the sixth thumb
key; along the home key row: Y assigned to the seventh home key, S
assigned to the eighth home key, T assigned to the ninth home key,
N assigned to the tenth home key, D assigned to the eleventh home
key, and C assigned to the twelfth home key; along the upper letter
key row: F assigned to the eighth upper letter key, V assigned to
the ninth upper letter key, M assigned to the tenth upper letter
key, P assigned to the eleventh upper letter key, and Q assigned to
the twelfth upper letter key; along the lower letter key row: G
assigned to the lower letter key situated between the eighth home
key and the operator, Z assigned to the lower letter key situated
between the ninth home key and the operator, N assigned to the
lower letter key situated between the tenth home key and the
operator, B assigned to the lower letter key situated between the
eleventh home key and the operator, and J assigned to the lower
letter key situated between the twelfth home key and the operator;
and on thumb keys: the backspace assigned to the thumb key situated
between the fifth thumb key and the operator, and the tabulator
assigned to the thumb key situated at the inner end of the lower
letter key row in the center of the keyboard as viewed by the
operator.
16. A keyboard, as in claim 11, for the French language comprising
character and control keys arranged in serial order along key rows
as viewed by the operator from the outer edge of the keyboard to
the center of the keyboard as follows:
on the left hand side of the keyboard as viewed by the operator:
along the thumb key row: O assigned to the first thumb key, the
space assigned to the second thumb key, and the carriage return
assigned to the third thumb key; along the home key row: Y assigned
to the first home key, A assigned to the second home key, I
assigned to the third home key, E assigned to the fourth home key,
U assigned to the fifth home key, and (lower case: comma; upper
case comma) assigned to the sixth home key; along the upper letter
key row: (lower case: circumflex; upper case circumflex) assigned
to the second upper letter key, X assigned to the third upper
letter key, the shift assigned to the fourth upper letter key,
(lower case: period; upper case: period) assigned to the fifth
upper letter key; and (lower case: hyphen; upper case: underline)
assigned to the sixth upper letter key; along the lower letter row:
(lower case: question mark) assigned to the lower letter key
situated between the second home key and the operator, and (lower
case: accent acute; upper case: accent acute) assigned to the lower
letter key situated between the fifth home key and the operator;
and on thumb keys, the shift lock assigned to the thumb key
situated between the second thumb key and the operator, and the
margin release assigned to the thumb key situated at the inner end
of the lower letter key row in the center of the keyboard as viewed
by the operator; and
on the right hand side of the keyboard as viewed by the operator:
along the thumb key row: M assigned to the fourth thumb key, N
assigned to the fifth thumb key, and F assigned to the sixth thumb
key; along the home key row: G assigned to the seventh home key, S
assigned to the eighth home key, T assigned to the ninth home key,
R assigned to the tenth home key, L assigned to the eleventh home
key, and D assigned to the twelfth home key; along the upper letter
row: X assigned to the seventh upper letter key, V assigned to the
eighth upper letter key, P assigned to the ninth upper letter key,
and C assigned to the tenth upper letter key, H assigned to the
eleventh upper letter key, and J assigned to the twelfth upper
letter key, and along the lower letter key row: B assigned to the
lower letter key situated between the eighth home key and the
operator, and C situated between the tenth home key and the
operator, Q situated between the eleventh home key and the
operator, and Z situated between the twelfth home key and the
operator; and on thumb keys: the backspace situated between the
fifth thumb key and the operator, and the tabulator assigned to the
thumb key situated at the inner end of the lower letter row in the
center of the keyboard as viewed by the operator.
17. A keyboard, as in claim 12, for the German language comprising
character and control keys arranged in serial order along key rows
as viewed by the operator from the outer edge of the keyboard to
the center of the keyboard as follows:
on the left hand side of the keyboard as viewed by the operator:
along the thumb key row: O assigned to the first thumb key, the
space assigned to the second thumb key, and the carriage return
assigned to the third thumb key; along the home row: A assigned to
the second home key, U assigned to the third home key, E assigned
to the fourth home key, I assigned to the fifth home key, and the
shift assigned to the sixth home key; along the upper letter row:
(lower case: question mark) assigned to the second upper letter
key, (lower case: period; upper case: period) assigned to the third
upper letter key, (lower case: umlaut; upper case: umlaut) assigned
to the fourth upper letter key, (lower case: comma; upper case:
comma) assigned to the the fifth upper letter key, and (lower case:
hyphen; upper case: underline) assigned to the sixth upper letter
key; and on thumb keys: the shift lock assigned to the thumb key
situated between the second thumb key and the operator, and the
margin release situated at the inner end of the lower letter key
row in the center of the keyboard as viewed by the operator;
and
on the right hand side of the keyboard as viewed by the operator:
along the thumb key row: L assigned to the fourth thumb key, N
assigned to the fifth thumb key, M assigned to the sixth thumb key;
along the home key row: W assigned to the seventh home key, R
assigned to the eighth home key, S assigned to the ninth home key,
T assigned to the tenth home key, H assigned to the eleventh home
key, and D assigned to the twelfth home key; along the upper letter
key row: (lower case: .beta.) assigned to the seventh upper letter
key, F assigned to the eighth upper letter key, G assigned to the
ninth upper letter key, C assigned to the tenth upper letter key, B
assigned to the eleventh upper letter key, and Z assigned to the
twelfth upper letter key; along the lower letter key row: V
assigned to the lower letter key situated between the eighth home
key and the operator, K assigned to the lower letter key situated
between the eleventh home key and the operator, and P assigned to
the lower letter key situated between the twelfth home key and the
operator; and on thumb keys: the backspace assigned to the thumb
key situated between the fifth thumb key and the operator, and the
tabulator assigned to the thumb key situated at the inner end of
the thumb key row in the center of the keyboard as viewed by the
operator.
Description
FIELD OF THE INVENTION
This invention relates to input keyboards for typewriters, computer
terminals, and other devices processing alphanumeric information,
and methods of designing optimum keyboards in any alphabetic
language. An input keyboard may be defined as an array of keys
operated by the fingers of both hands to transfer graphic
characters and control instructions to a machine. The keyboard thus
serves as an interface between a human operator and a machine
handling alphanumeric symbols. The output may include, but is not
limited to, visible characters on paper (typewriters), characters
on a flourescent screen (cathode ray tubes), holes in paper tapes
or cards (tape perforators, card punches), or changes in the
magnetization of tapes or disks (computer input stations).
DESCRIPTION OF THE PRIOR ART
The keyboard is an interface between man and the machines producing
this written language. During recent decades, major advances have
been made in the means of generating this written language.
Electric typewriters have replaced manual machines, Electronic word
processing devices are displacing electric typewriters, and
computer controlled photocomposers are surplanting linotype
machines. Yet despite these technical advances, an ancient,
inefficient keyboard devised a hundred years ago has remained
undisturbed.
Operators throughout the world use essentially the same keyboard,
even though they input material in a variety of alphabets whose
letters have different frequencies and combine in different ways.
Consequently operators are forced to struggle with a keyboard whose
arrangement of letters and controls disregards the properties of
the language they are processing and the geometry of the human
hand.
This incompatibility is a product of the history of the universal
keyboard, which is a direct descendant of the manual typewriter
invented in America a century ago. As early as 1878, the Remington
typewriter reproduced the arrangement of letters and punctuation
marks appearing on the contemporary keyboard. This American
keyboard was adopted as an international standard in 1888, and was
swiftly accepted in European countries with only minor
modifications to meet the needs of different languages. Thus on the
German keyboard, the o and a appear at the right-hand end of the
home row, and the y and z are interchanged because the y is
extremely rare in German. Similar changes have been made in other
European languages, but for practical purposes, their keyboards are
essentially equivalent. Such uniformity might be helpful if
individuals processed information in many languages, but this is
rarely the case. Instead operators are burdened with a keyboard
that ignores the statistical characteristics of their native
language.
The linotype keyboard used in printing is even more inefficient. It
consists of ninety keys arranged in six rows. Lower-case letters
are assigned to the left hand, and upper-case letters to the right
hand. Because of mechanical limitations in early linotype machines,
the commonest letters are alloted to the little and second fingers
of the left hand. The a, e, i, o, n and t are assigned to the
little finger, and the u, d, h, l, r, and s to the second finger.
This arrangement prevents rapid input because of the long vertical
reaches to strike keys in different rows and the large number of
successive strokes made by the little and second fingers of the
left hand. This clumsy layout is still retained in contemporary
linotype machines, even though the mechanical restrictions that
originally dictated this choice no longer apply.
The defects of the universal typewriter keyboard emerged fifty
years ago as the proficiency of typists improved and touch typing
became widespread. Today these deficiencies are even clearer.
Fingers dart over the standard keyboard executing complex stroking
patterns. The middle row is not a true home row. In English, 52% of
the letter strokes occur on the top letter row, 33% on the middle
row, and 15% on the bottom letter row.
The universal keyboard is a left-hand arrangement in a righthanded
world. The left hand executes more difficult strokes than the agile
right hand. Approximately 2,700 common words may be keyed by the
left hand, but only 300 by the right hand. Half the successive
letters in representative prose passages lie on the same hand,
which is the same fraction that would occur if the keys were
randomly distributed. Some of these sequences require three or four
strokes by the same hand, which are slower and more difficult to
complete than strokes on alternate hands. Many common digraphs must
be keyed by the same finger. Striking successive keys with the same
finger is very slow because fingers cannot prepare for a second
stroke while the first one is being made. Examples include
combinations involving the r and t, the c and e, the u and n, and
the l and o.
About 30% of the motions on the universal keyboard are hard to
execute. The include awkward reaches from the home row, successive
strokes by the same finger, and hurdles across the home row to
operate keys on the top and bottom letter rows. Because of the
absence of a true home row, mastering the standard keyboard demands
considerable dexterity, since the hands are in constant motion
reaching for keys on different rows.
The location of letters and controls ignores the varying strength
of individual fingers. Shift keys are operated by the little
finger, which requires considerable effort on manual machines.
Mechanical necessity a century ago fixed the geometric location of
keys, which has remained unchanged. The straight key rows do not
follow the contours of the hand; the staggered vertical key array
in adjacent rows are awkward to strike. Fingers must traverse
oblique paths to reach keys on different rows, and the weak little
fingers must operate the shift keys at the corners of the keyboard.
Such awkward movements produce muscular fatigue, since operators
may complete 50,000 to 80,000 key strokes during an average working
day.
Mastering the standard keyboard requires extensive practice. Modest
facility generally takes 50 to 100 hours. Resulting speeds usually
do not exceed three to five strokes a second even after lengthy
training. For every hour of practice, input rates typically
increase by only one stroke a minute, due to the complexity of
required finger movements. Error rates are essentially independent
of stroking skill, ranging from one to four errors a minute. Errors
are increased by the poor location of keys and the inefficient
arrangement of letters and controls. Errors are distributed over so
many possibilities, they cannot be effectively reduced by
practicing on a specialized vocabulary. Research studies show that
special exercises are ineffectual in improving keyboard facility.
All finger motions must be practiced at the same time using
ordinary English to supply letter combinations in accordance with
their natural frequency.
The standard keyboard has been repeatedly criticized in Europe
because of its American origin and neglect of Continental
linguistic differences. European languages cannot be processed
efficiently on this keyboard. In German, 46% of the successive
letter strokes are made by the same hand, which is close to the
values for a random arrangement of letters. The left hand executes
58% of the letter strokes--the more agile right hand 42%. The eight
keys directly under the fingers account for only 24% of the letter
strokes on the German keyboard. The middle row is not a true home
row, since 49% of the strokes are made on the top letter row, 32%
on the middle row, and 19% on the bottom row.
For several generations, inventors have sought to correct the
deficiencies of the universal keyboard. They have proposed setting
common letters directly under the eight fingers of both hands to
reduce stroking movements and make the middle row a true home row.
They have advocated curved key rows to fit the hand, and raised key
tops to compensate for differences in finger length. They have
suggested splitting the keyboard in two, and moving the shift keys
to the center of the keyboard to be operated by the thumb or fourth
fingers. These geometric innovations, however, have been frustrated
by the poor arrangement of letters and controls which masks any
improvements due to spacial changes.
The standard keyboard has remained unchanged, despite its defects.
Manufacturers would not make typewriters with a new keyboard unless
a market existed for them. Businessmen would not order such
machines unless employees could operated them. Schools would not
teach a new keyboard unless it was used by the business world. The
ensuing impass has blocked progress and left the universal keyboard
firmly entrenched.
A new keyboard will not be adopted unless it yield substantial
economic benefits. Initially the most promising applications will
be in fields where input is a major expense. An example is
computerized typesetting where keyboarding now represents
approximately 80% of the cost. Another field is data processing,
where data input accounts for about 40% of the expense.
Considerable savings should be possible because operators currently
execute an averagee of 12,000 strokes an hour (three characters a
second) during a working day.
To win commercial acceptance, a new keyboard must lead to faster
entry (50 to 100%) and lower error rates. To overcome entrenched
resistance, employees must be able to acquire stroking facility in
a short time (100 hours or less), and secure greater speed and
accuracy after brief training than is possible on the standard
keyboard after extended practice.
Rapid entry depends on the skill and training of operators, as well
as the layout and arrangement of the keys. Efficient training is
important because of the initial absence of skilled operators and
the reluctance of experienced personnel to exchange a keyboard they
know for one that is unfamiliar. Individuals must be taught who are
already proficient on the standard keyboard, as well as those who
have little or no experience. Instruction must lead quickly to
stroking facility and confirm the ease of mastering a new key
arrangement. Swift progress during early training is necessary to
win acceptance and encourage executives to bear the cost and
inconvenience of teaching employees to operate new equipment.
Previous inventors have slighted the problem of teaching a new key
configuration. They have presented calculations of stroking
efficiency, but ignored the fact that substantial differences
between competing designs do not appear until considerable entry
speeds are reached. At low and moderate rates (below five
characters a second) the presence of awkward movements is masked
because keys are stroked one at a time. At higher rates, clumsy
movements impair performance by hindering chain stroking in which
one finger prepares for a stroke while another one is being made.
This gap in entry rates from one character to five characters a
second is precisely the difference that separates a novice from a
skilled operator on the standard keyboard. Unless this gap can be
bridged quickly and economically, the utility of a new keyboard
will be nullified by the expense and difficulty of reaching skills
where its superiority becomes evident.
Earlier inventors have failed to develop effective instruction
materials that lead to fast input and early chain stroking. The
history of the Dovrak-Dealey keyboard is revealing in this respect.
Ever since its invention in 1932, the Dvorak keyboard has been
advocated as a replacement for the universal keyboard. Its
advantages have been described in newspapers, magazines, and
technical journals, but despite this publicity, the keyboard has
not gained a foothold in the business world.
A major reason is the absence of learning materials that utilize
the simplified motions occurring on the Dvorak keyboard. Training
exercises have mimicked instruction methods employed on the
standard keyboard by concentrating on individual letters rather
than stroking sequences. Consequently most operators who learn the
Dvorak keyboard do not acquire chain stroking, and are unable to
demonstrate its superiority under actual working conditions.
Sound keyboard design and effective instruction must be based on
the statistical properties of the language and the kinesthetic
capacity of the brain and fingers. Setting common letters directly
under the fingers of each hand improves stroking efficiency.
Additional principles are required, however, to fix the arrangement
of letters because of the large number of possible
permutations.
Eight letters can be arranged in 8!=40,320 ways. If the most
frequent vowel and the most frequent consonant are placed under the
third finger of each hand, 6!=720 distinct keyboards can be formed
with the remaining six letters. Finally, if four common vowels are
set under the fingers of one hand, and four common consonants under
the fingers of the other hand, 4!.times.4!=576 arrangements are
possible.
In view of this host of alternatives, when even a small number of
keys is involved, further principles must be employed to reduce the
number of possibilities and restrict competing designs to a few
keyboards possessing comparable efficiencies. Alternate designs
must be evaluated numerically, since direct experimental tests are
not feasible. Such tests are ruled out because of the time and
expense of training operators, the large number of subjects
required for statistically valid results, and the contamination of
test scores by variations in the skill, instruction, and practice
materials used by operators on different keyboards.
Empirical studies reveal that the fastest strokes are made on
alternate hands when one finger prepares to make a stroke while
another finger is striking a key. The time taken to complete
successive strokes increases with their motor difficulty. These
strokes are in order of difficulty: strokes on home keys by
alternate hands; strokes on different rows by alternate hands;
strokes on home keys by the same hand; strokes on a home key and a
key in another row by different fingers of the same hand; strokes
outside the home keys by different fingers of the same hand; and
strokes on different keys by the same finger.
For skilled operators, the slowest strokes take three times longer
than the fastest ones. Therefore for rapid entry, a majority of
successive strokes should be made by alternate hands on home keys,
and a minimum by the same finger on different keys.
Dvorak and Dealey applied these findings to develop a simplified
keyboard for the English language based on kinesthetic and
linguistic principles (U.S. Pat. No. 2,048,248). They recognized
that twoletter combinations must be considered as well as single
letter frequencies because the time required for a particular
stroke depends on its immediate predecessor. Dvorak and Dealey
employed a table of English digraph frequencies to determine the
letter arrangement on their simplified keyboard. They set vowels on
the home row of the left hand--and high-frequency consonants on the
home row of the right hand. Punctuation marks and rare consonants
were assigned to the left hand--and the remaining consonants to the
right hand.
This choice remedies many of the faults of the standard keyboard.
Separating vowels and consonants increases alternate hand motions.
Placing consonants under the right hand insures that a majority of
two-letter digraphs are stroked by the agile right hand. Dvorak and
Dealey demonstrated the superiority of their keyboard by
calculating the relative frequency of different strokes and
comparing them with those on the standard keyboard which overworks
some fingers and demands many difficult stroking motions. Dvorak
and Dealey catalogued these difficult motions and proved
numerically that operating the universal keyboard is a taxing
kinesthetic task.
Although the Dvorak keyboard marked a major advance, it has
significant limitations. It retains the clumsy geometric
configuration of the standard keyboard with its crooked reaches to
adjacent rows--and leaves shift keys at the corners to be stroked
by the little finger. Operating the Dvorak keyboard requires only
nine fingers--eight fingers to input the letters, and a thumb to
strike the space bar. The placement of letters is not optimum. The
p appears on the vowel side of the keyboard, which leads to many
one-hand motions. The u lies under the fourth finger of the left
hand, rather than the i which occurs twice as often.
On the theoretical side, the Dvorak-Dealey table of digraphs is
incomplete. It omits double letters which account for 1.7% of the
letters and spaces in English. It also ignores the space, although
the space is the commonest character in English, accounting for one
out of every six characters. (The same mistake was made by Roy
Griffin who proposed a "Minimotion" keyboard based on an elaborate
statistical study of digraph frequencies that erroneously
disregarded the space separating words.) Space-letter digraphs are
important because a majority of words begin and end with a
consonant on the right side of the keyboard. Therefore using the
right thumb to stroke the space bar on the Dvorak keyboard,
following the practice on the standard keyboard, leads to many
onehand strokes.
SUMMARY OF THE INVENTION
Accordingly it is a principal object of this invention to supply a
general-method of designing keyboards in any alphabetic language
that maximizes the speed and accuracy with which a human operator
can transfer alphanumeric information to a machine.
Another object of this invention is to present the complete optimum
keyboard for the English language, and optimum keyboards containing
the most important letters and symbols for German, French, Italian,
Spanish, and Portuguese.
Another object of this invention is to provide a keyboard utilizes
all ten fingers to enter alphabetic material and control
instructions. Another objective is to furnish a keyboard that
lightens the stroking load on the fingers and increases the
separation of vowels and consonants by assigning character and
control keys to both thumbs.
Another object is to base keyboard design on the neural capacity of
the brain and fingers, and the statistical properties of alphabetic
texts. Another object is to minimize stroking errors and finger
movements by allocating characters in accordance with their
statistical frequency. Another aim is to furnish an optimum letter
arrangement for any alphabetic language by means of a frequency
count of 100,00 characters without a detailed knowledge of the
language.
Another aim is to reduce keyboarding to a set of simple,
independent finger motions. Another object is to maximize
successive strokes on alternate hands by assigning consonants to
the right hand--and vowels, punctuation marks, diacritical marks,
and rare consonants to the left hand. Another object is to minimize
successive strokes by the same finger, and essentially eliminate
triple strokes by the same hand by separating vowels and consonants
in the keyboard. Another objective is to utilize the greater
dexterity of the right hand in processing two-letter combinations
by assigning consonants to the right hand. Another goal is to
provide a keyboard that reduces substitution errors by alloting
characters of widely different frequencies to the same finger.
Another goal is to make touch typing automatic by placing ten
common characters directly under the fingers. A further goal is to
increase the speed of numerical input by assigning odd digits to
the left hand, and even digits to the right hand.
An object of this invention is to supply a keyboard that reducess
fatigue by fixing horizontal and vertical key positions to conform
with the architecture of the hand. Another object is to decrease
stroking errors by dividing the keyboard into two separate
sections. A further object is to lessen muscular tension by
rotating each section of the keyboard, so the forearm, wrist, and
hand lie in a straight line from the shoulder. Another objective is
to reduce digital strain by curving key rows to follow the geometry
of the hand. Another objective is to equalize stroking motions by
raising key tops to compensate for differences in finger length.
Another goal is to to permit the home position to be located by
touch by varying the height of home keys. Another goal is to ease
stroking by inclining the thumb row from flexure to extension. A
further goal is to simplify numerical input by means of vertically
oriented stroking surfaces on the number row that can be operated
by a horizontal motion of extended finger tips.
Another object of this invention is to provide a keyboard that
generates common two-character combinations by simultaneously
operating two home keys. Another object is to make these
simultaneous chord strokes easy to execute by using key-pairs under
adjacent fingers, or the thumb and another home key. Another goal
is to furnish a keyboard that expedites learning these chords by
making their output identical with the keys struck in a majority of
cases. An additional goal is to utilize remaining chords to reduce
movements from the home row and eliminate clumsy finger
motions.
An object of this invention is to provide a keyboard which
generates upper-case characters by means of a single shift key that
acts on one character and automatically returns the system to
lowercase operation. Another object is to replace multiple strokes
after certain punctuation marks by a single stroke. Another object
is to pass from one sentence to another by a single stroke, and
from one paragraph to another by means of a single chord. Another
objective is to eliminate carriage return strokes by automatically
advancing the system to the next line when a space or hyphen key is
operated within a given number of spaces from the end of a
line.
Another objective is to reduce the number of keys on foreign
language keyboards by employing a single dead key for individual
diacritical marks.
Another aim of this invention is to provide a keyboard that enables
stroking facility to be acquired rapidly by practicing on a limited
repertory of finger movements that occur frequently in natural
texts. Another aim is to supply a keyboard that hastens chain
stroking by allowing instruction to concentrate on alternate-hand
strokes on home keys, and permits numerical input to be mastered by
practicon digits arranged in alternate-hand sequences.
Another object of this invention is to decrease the training time
of average operators and to increase their entry speed by
simplifying keyboard motions. A final object is to provide
keyboards that allow training methods developed for one language to
be applied to other languages.
KEYBOARD ARRANGEMENT
This invention describes a systematic method of designing optimum
keyboards in any alphabetic language for typewriters, computer
terminals, and other devices processing alphanumeric information.
The design maximizes input rates and stroking accuracy, and
minimizes finger motions and the time required to learn the
keyboard. The invention assigns characters and controls to both
thumbs, setting common characters directly under the fingers of
both hands.
The space and vowel keys are alloted to the right hand, and
consonants to the right hand. A majority of successive strokes are
on alternate hands--a minimum on the same finger. Three out of four
strokes occur on home keys directly under the fingers, permitting
rapid acquisition of keyboard facility. The speed of chord stroking
is combined with the ease of serial input by employing two-key
chords to enter common two-character combinations on the same side
of the keyboard. Double letters are generated by holding down the
corresponding letter key.
Keys are spacially arranged to fit the hand. The keyboard is
divided into the two separate halves. Each half is rotated about
15.degree., so the hand, wrist, and forearm lie in a straight line
from the shoulders when fingers rest on the home keys. Key rows are
curved to follow the shape of the hand. Key tops have variable
heights to compensate for differences in finger length. Key tops
outside the home row are tilted for easy stroking from the home
position. The thumb row is inclined to follow the thumb from
flexure to extension; its keys are recessed to prevent them from
being struck accidently by the fourth finger. Stroking surfaces on
the number row are vertically oriented, so they can be operated by
a horizontal motion of extended finger tips.
Consonants are set on the right side of the keyboard. Vowels,
punctuation marks, diacritical marks, and rare consonants are on
the opposite side of the keyboard. The space key lies under the
left four high frequency vowels directly under the remaining
fingers of the left hand. Five high frequency consonants lie
directly under the fingers of the right hand. In most European
languages, these nine characters correspond to the commonest vowels
and consonants in the language. The left thumb row is completed by
another vowel and the carriage return key; and the right thumb row
by two more consonants.
The four common vowels that lie directly under the fingers of the
left hand are: a, e, i, and o in English, Italian, Spanish, and
Portuguese. The five high frequency consonants that lie directly
under the fingers of the right hand are: n, r, s, t, and h in
English and German. The u replaces the o as one of the home vowels
in German and French. The l replaces the h in French and Italian;
and the d replaces the h in Spanish and Portuguese.
These letters are arranged on home keys so that common digraphs on
the same hand may be stroked by adjacent fingers, or by the thumb
and another finger. Operating these key-pairs simultaneously, plus
the pair keyed by the little and fourth fingers furnishes sixteen
chord, eight on each hand. These chords are used to enter leading
digraphs, such as vowels and spaces at the beginning and end of
words, plus common consonant combinations (such as th, st, and ng
in English).
The number row is split into even and odd portions. Odd digits are
assigned to the left hand--even ones to the right hand. Dead keys
produce diacritical marks in foreign languages, but do not advance
the system in the horizontal direction. A single shift generates
upper-case characters. This key acts on only one character,
automatically returning the system to lower-case operation.
Striking the space and hyphen keys within a given number of spaces
from the end of a line automatically advances the system to the
next line.
The lower-case period generates the multiple characters needed to
go from one sentence to another. Chord strokes produce the
characters reequired to pass from one paragraph to another.
Operating the lower-case comma, colon, or semi-colon keys
automatically produces a space after each of these punctuation
marks. Operating the uppercase period and comma key produces the
period and comma appearing in decimals, numbers, and
abbreviations.
For the English language, the location of letters and symbols on
the keyboard is, going from the little to the fourth finger, as
follows:
On the left hand: on the number row--(open bracket/slash), 1, 3, 5,
7, and 9: on the top letter row--(open parenthesis/colon),
(semi-colon/question mark), x, shift, period, and
(underline/hyphen); on the home row--y, i, o, e, a, and comma; on
the bottom letter row--j, z, and (exclamation point/apostrophe); on
the thumb row--u, space, and carriage return, plus margin release
and shift lock.
On the right hand: on the number row--(close brackets, onehalf), 0,
8, 6, 4, 2; on the top letter row--(close parenthesis/double
quotation marks), b, c, m, f, and k; on the home row--g, r, s, t,
h, and d; on the bottom letter row--v, p, and q; and on the thumb
row--l, n, and w, plus tab and back space.
Simultaneously operating two keys by the same hand generates the
following output:
On the left hand: (space, e) produces e then space; (space, i)
produces space then i; (space, a) produces space then a; (space, o)
produces space then o; (i, o) produces io, (e, a) produces ea; (e,
o) produces ou; (i, a) produces y then space; (shift, period)
produces a period, carriage return, tab, and a shift; and (shift,
question mark) produces a period, two carriage returns, and a
shift.
On the right hand: (t, h) generates th; (s, t) generates st; (r, s)
generates rs; (r, h) generates ch; (n, t) generates nt; (n, s)
generates ns; (n, h) generates nd; and (n, r) generates ng.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is top view of the keyboard for the English language
illustrating the location of letter and control keys, and the
spacial division of the keyboard into two rotated halves containing
curved key rows that follow the shape of the hand.
FIG. 2 is a cross-section through aa home row taken along the line
2--2 of FIG. 1 illustrating the variable heights of key tops in a
given row, and the inclined key tops outside the home position.
FIG. 3 is a cross-section through a thumb row taken along the line
3--3 of FIG. 1 illustrating the inclined thumb key tops outside the
home position.
FIG. 4 is a cross-section through a vertical set of keys at the
inner boundary of the keyboard taken along the line 4--4 of FIG. 1
illustrating the recessed thumb keys, the inclined key tops outside
the home position, and the vertically oriented key tops on the
number row.
FIG. 5 is a top view of part of the keyboard illustrating the
location of the most important letters and symbols for the Italian
language.
FIG. 6 is a top view of part of the keyboard illustrating the
location of the most important letters and symbols for the
Portuguese language.
FIG. 7 is a top view of part of the keyboard illustrating the
location of the most important letters and symbols for the Spanish
language.
FIG. 8 is a top view of part of the keyboard illustrating the
location of the most important letters and symbols for the French
language.
FIG. 9 is a top view of part of the keyboard illustrating the
location of the most important letters and symbols for the German
language.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The Ten-Finger Keyboard
The optimum keyboards presented in this invention correct each of
the shortcomings described above.
The keyboards of this invention are ten-finger keyboards which
employ both thumbs as well as other fingers, and fully utilize the
stroking capacity of the thumbs to enter letter and control
instructions. Using both thumbs for input has many advantages. The
thumbs are the strongest finger and possess the greatest freedom of
movement. Thumb keys can be operated without disturbing other
fingers. Successive or simultaneous strokes of a home thumb key and
another home key by the same hand can be readily executed because
of the way the thumb is joined to the hand.
Ten-finger keyboards have been introduced in the past in
stenographic machines, telegraphic terminals, and chord
typewriters. On stenographic machines, words are represented by an
initial consonant cluster chorded by fingers of one hand, followed
by a vowel cluster stroked by the thumbs, terminated by a second
consonant cluster chorded by the fingers of the second hand.
The thumbs serve a different function in the present invention. The
left thumb rests on the space key on the vowel side of the
keyboard, flanked by a vowel on one side and a carriage return on
the other. The right thumb rests on a common consonant on the
opposite side of the keyboard, flanked by two less frequent
consonants. Using the thumb to enter consonants permits more choice
in arranging letters and improves the separation of vowels and
consonants.
Distributing consonants on all five fingers is a marked asset
because consonants outnumber vowels in nearly all alphabetic
languages. English has six vowels and twenty consonants (five of
which occur often). Comparable proportions occur in other European
languages. Thumb input allows five high frequency consonants to be
placed directly under the fingers. Setting common characters under
each finger insures that most strokes will lie on home keys. In
English and most European languages, the ten home-key characters
account for roughly three out of four key strokes. Consequently the
arrangement of letters on the home keys determines the basic layout
of the keyboard.
Assigning characters to both thumbs allows letters to be
distributed more efficiently. It lightens the kinesthetic load on
other fingers, and enables controls (shift, tab, carriage return)
to be placed in the center of the keyboard. Alloting letters to all
ten fingers reduces stroking errors and accelerates learning by
differentiating the muscular sensations and spacial positions
associated with particular letters. Thumb keys also eliminate the
need for keys on the lower letter row assigned to the second and
third finger which are difficult to stroke.
Determining the best arrangement of characters and controls on a
keyboard involves awkward compromises. For maximum performance, a
number of simultaneous conditions must be satisfied that may be
incompatible. The larger the number of alternatives, the smaller
the compromise required to meet these conditions. Assigning letters
to the thumb permits the keyboard to be tailored to the language
being processed. Using all ten fingers for input multiplies the
number of ways letters can be alloted to individual fingers. On the
consonant side of the keyboard, the five home keys can be arranged
in 5!=120 different ways. On a conventional keyboard with four home
keys, only 4!=24 permutations are possible.
Thumb entry leads to greater freedom in choosing letters outside
the home position because they can be placed on an additional
finger. Since two letters may be assigned to n fingers in n(n-1)
ways, a pair of consonants may be distributed in twenty ways on
five fingers, but in only twelve ways on four fingers. This
increase simplifies stroking motions and aids accurate entry of
common digraphs because letters may be arranged so these digraphs
can be stroked by adjacent fingers, or by the thumb and another
finger. Seven such strokes exist on each hand on the ten-finger
keyboard (three on adjacent keys, and four involving the thumb),
but only three are possible on the standard keyboard.
Kinesthetic Constraints
A fundamental analysis of keyboard design must consider two
factors: the capacity of the brain to direct the fingers to strike
an ordered sequence of keys, and the statistical properties of the
language being processed. The first factor belongs to the field of
human physiology. It controls the rate at which operators learn a
new keyboard and the stroking rates they achieve after extended
practice. The second factor belongs to the area of linguistics. It
determines the optimum arrangement of characters on the
keyboard.
Since a keyboard is an interface between man and the machine, the
physiological capacity of the operator must be considered in
setting realistic performance goals and developing effective
methods of learning a new key configuration. Earlier inventors have
erroneously assumed that an efficient key arrangement would
automatically solve the problems of keyboard learning and eliminate
the kinesthetic constraints imposed by the brain and fingers. But
this is not the case.
Entry rates on the standard keyboard fall far below physiological
limits. A fast typist may stroke 5 to 9 keys a second
(corresponding to 50 to 90 six-character words a minute) on a
typewriter whose mechanical speed may vary from 10 to 18 characters
a second. Measured tapping rates, however, are much greater. For a
15 second test, maximum tapping frequencies have been reported as
high as 48 a second for the little finger of the left hand, and 70
taps a second for the fourth finger of the right hand. These
frequencies mount in moving across the hand from the little to the
fourth finger.
The time taken to execute a stroke increases with its difficulty
and complexity; measured response times lengthen as visual stimuli
and motor responses diverge. Thus skilled operators on stenographic
machines execute only three chord strokes a second, because they
must depress several keys simultaneously, and the output generated
does not bear a simple relation to the keys depressed. (This slow
input is offset by extensive use of stenographic
abbreviations.)
Keyboarding involves conversion of visual stimuli into finger
motions through the mediating action of the brain. This task is not
performed efficiently because mental associations between
alphabetic stimuli and key strokes are hard to establish. The brain
has a limited memory for motor movements and attaches a single
conditioned reflex to each visual cue. As a result, mastering a new
letter arrangement effectively destroys the kinesthetic
associations previously established for an earlier arrangement.
Learning behavior illustrates the difficulty of connecting
alphabetic stimuli with stroking responses. Students must give
keyboarding their undivided attention, expending considerable
mental effort to "tell" the brain which key to strike. Deciding on
the appropriate finger motion is initially slow and laborious.
Novices may take a second to strike each key. Often they attempt to
make learning easier by siliently vocalizing letters they are
trying to strike, striving to reinforce the weak connection between
visual and stroking responses by auditory associations.
Lengthy practice is required before one finger can prepare for a
stroke while another one is being made (chain stroking). At first
the brain processes only on character at a time. Gradually more
information is handled as entry speeds increase. Observation
reveals that operators adjust their intake to their stroking speed
--reading "one second ahead" to supply the brain with the number of
characters they can stroke in one second.
The contrast between the arduous acquisition of keyboarding and
man's gift for speech is striking. People can learn to speak
several languages and easily switch from one to another, employing
a vocabulary of thousands of words. But they can learn only a small
repertory of finger motions. Although individuals may speak several
languages, they can operate by touch only a single keyboard using
the Roman alphabet because their motor response to a given
alphabetic stimulus is fixed. This limitation is due to the
organization of the brain, rather than differences in the muscular
capability of the fingers, the larynx and vocal chords.
The disparity between human speech and keyboard ability may be
explained by man's early history. Natural selection favored the
development of a "speech-making" brain, because speech was a
powerful asset in a hostile environment. Primitive man used his
hands to hunt, gather food, build shelter, and fashion tools and
weapons. But these manual tasks are far removed from the motions
and associations required for keyboarding. Therefore man's brain is
not suited for transforming visual cues into finger strokes, since
this activity has no counterpart in his early history.
The brain's kinesthetic inefficiency has important consequences for
keyboard design. A successful configuration must employ a small
vocabulary of finger motions that should be easy to execute. Motor
choices alloted to any finger should be limited, and a majority of
successive strokes occur on alternate hands to exploit the cerebral
independence of opposite-hand motions. Finger strokes on each side
of the keyboard are controlled by different regions of the brain;
left-hand strokes by the right hemisphere of the brain; and
right-hand strokes by the left hemisphere of the brain. This
provides a neurological basis for chain stroking where the fingers
of opposite hands move independently. Keyboard learning is
facilitated when characters assigned to each hand possess common
linguistic features that enable them to be swiftly identified with
the appropriate stroking hand (governed by the opposite hemisphere
of the brain). This is true for the optimum keyboards of this
invention which allot consonant keys to the right hand, and space
and vowel keys to the left--and even and odd digits to opposite
hands.
Keyboards that assign many alternatives to individual fingers place
a heavy processing load on the brain. Learning times for such
keyboards are excessive--their input rates slow. An example is
Ayres' word writing machine (U.S. Pat. No. 3,225,883) which has a
separate set of consonants and vowel keys for letters at the
beginning and end of words. Another example is Seibel's
communication device (U.S. Pat. No. 3,022,878) which uses
transducers connected to the joints of each finger to translate
digital orientations into chord strokes. More than a thousand
different chords can be produced on this device by the fingers of a
single hand. Experiments show, however, that motor learning is not
completed on this device, even after 75,000 trials, because of the
great number of chords available. Consequently its great
information handling capacity is dissipated by the long time needed
to learn these chords, and the high error rates associated with
their large number.
The ten-finger keyboards of this invention reduce the kinesthetic
alternatives alloted to each finger by assigning characters to all
ten fingers. These keyboards lighten the processing load on the
brain by setting common characters directly under the fingers, so
that three out of four strokes may be executed by simply depressing
keys under the fingers. In addition, they aid learning by
separating vowels and consonants, so that seven out of ten strokes
lie on alternate hands. Finally, these keyboards permit common
one-hand digraphs to be stroked easily by alloting two-charater
combinations to adjacent fingers, or the thumb and another
finger.
KEYBOARD GEOMETRY
Engineering the keyboard to fit the hand simplifies the motor
movements required and reduces the neural instructions that must be
transmitted from the brain to the fingers. Making vertical and
horizontal key positions conform with the human hand eliminates
clumsy stroking motions, resulting in lower error rates and less
muscular fatigue.
The ten-finger keyboard is split into two symmetric halves; one for
each hand, as shown in FIG. 1:1, 2. The half operated by the right
hand is rotated clockwise about 15.degree.; the half operated by
the left hand is rotated counter-clockwise about 15.degree.--so
that when the fingers of each hand rest on their respective home
keys 9, 10, 11, 12, 15, the forearm, wrist and hand extending from
the shoulder lie on a straight line on each side of the keyboard.
This arrangement eliminates sources of muscular tension and
increases the spacial segregation of vowel and consonant
strokes.
Key rows are set in curved convex arcs to follow the natural
curvature of the hand--FIG. 1: 3, 4, 5, 6. Keys above and below
home row 5 are placed so that when fingers resting on home keys
straightened, they pass over the center of the inclined keys on the
upper letter row 4 and strike the center of keys of the vertically
oriented keys on the number row 3. When fingers on home keys are
bent, they pass over the center of the inclined keys on the lower
letter row 6. This makes it easier for fingers initially on the
home row to strike keys on adjacent rows.
Dividing the keyboard into two separate sections produces an
irregular contour that furnishes useful visual cues in learning key
locations at the extremities of the keyboard. It also prevents the
fourth finger of one hand from erroneously striking keys in the
center of the keyboard assigned to the opposite hand, which occurs
on solid key arrays.
Straightening the reaches from the home keys provides more
assurance in operating keys in other rows because fingers must be
merely bent or straightened to reach these keys. The curved key
array also simplifies operating keys at the extremities of the
keyboard, since these keys are symmetrically placed. Finally,
straightening the paths to adjacent keys permits true typing on the
number row. This is virtually impossible on the standard keyboard
because the irregular relation between keys on the home and number
rows forces even skilled typists to rely on visual cues to enter
digits accurately.
To facilitate numerical input, stroking surfaces on the number row
are vertically oriented, as illustrated in FIG. 4. These keys can
be struck by a horizontal motion of extended finger tips from the
home position. Accuracy is enhanced because number keys may be
stroked by straightening the fingers, which is easier
kinesthetically than extending a finger horizontally and then
striking down on a horizontal key top. The vertically oriented
surfaces on the number row slope away from the home row, as
illustrated in 21 of FIG. 4, to reduce the likelihood that a finger
nail rather a finger tip will strike the vertical key. Tilting
these key surfaces away from the home row also improves sight lines
to the number row, allowing mixed visual and tactile cues to be
used in entering numerical data.
Key heights on the ten-finger keyboard vary to compensate for
differences in finger length, as illustrated in FIG. 2. Keys
operated by the little finger 8, 9 are tallest, followed by the
fourth finger 12, 13, then by the second finger 14, and finally by
the third finger 15.
Varying the heights of individual keys increases stroking speed and
comfort, particularly for the little finger. Equalizing motor
movements associated with different fingers, permits faster entry
of chords involving adjacent fingers, especially for the little
finger. A vertically contoured keyboard enables hands to be placed
on home keys using tactile cues without viewing the keyboard. Such
cues are absent on the standard keyboard where all keys have the
same height. (On the standard keyboard, the right hand is often
misplaced side of the home row.)
Thumb input permits keys to be spread over a greater
area--supplying spacial associations that supplement muscular
sensations in differentiating vowel and consonant strokes. The
thumb keys 14, 15, 16, 17, 18, indicated by squares in FIG. 1,
protrude from a recessed plane. Their tops lie deeper than key tops
operated by the fourth finger, as illustrated in FIG. 4. This
variation in height prevents the thumb or fourth finger from
mistakenly striking keys on adjacent rows.
The thumb row 7 is inclined at a oblique angle to follow the
movement of the thumb from extension to flexure. This permits more
precise striking of the three thumb keys 14, 15, 16 on the thumb
row because these keys lie directly under the thumb when it is bent
from flexure to extension.
On the ten-finger keyboard, hands remain poised over the home row
while keys on other rows are operated. Key strokes to adjacent rows
are simplified by sloping key tops outside the home position as
illustrated in FIG. 4. Key tops on the lower letter row 6 and the
upper letter row 4 slope toward the home row 5 which rests in a
slight trough. Key tops are inclined so that key edges nearest the
home position lie deeper than key edges farthest from the home
position. Keys at the end of the home row 8, 13 slope toward
nieghboring home keys, facilitating return of the little and fourth
fingers to their home positions, as shown in FIG. 2. Thumb key tops
outside the home position 14, 16, 17, 18 slope toward the flat home
thumb key 15 on which the thumb normally rests, as illustrated in
FIG. 3. The edge of thumb keys nearest the home key lie deeper than
the edge farthest from the home thumb key, expediting return of the
thumb to its home position.
Thumb keys replace keys on the lower letter row alloted to the
second and third finger on the standard keyboard that are difficult
to stroke. (These keys may be retained to accomodate diacritical
marks and additional letters in foreigh languages, or the 96
characters of the ASCII character set used in computer input and
optical character recognition devices.) Eliminating keys operated
by the second and third fingers on the lower letter row reduces the
number of strokes to this row and increases the geometrical
isolation of keys at the lower extremities of the keyboard. This in
turn reduces substitution errors caused when adjacent fingers
mistakenly strike neighboring letters on solid key arrays. A
similar increase in accuracy occurs on the thumb row whose keys are
isolated from the rest of the keyboard.
Linguistic Statistics
Stroking motions depend on the character sequences in the language
and the distribution of letters on the keyboard. Before describing
a systematic procedure of arranging letters that minimizes finger
motion in any alphabetic language that can be keyboarded, it is
useful to examine the general characteristics of natural languages
(as distinguished from artifical codes or cryptographic
ciphers).
Natural texts are ordered strings of symbols carrying information.
The number of letters employed must be large enough to reproduce
the vocabulary and sounds of the language, yet small enough to
limit the number of rare or redundant characters. In most European
languages, this requires 24 to 32 letters, which can be readily
keyboarded. But the number may vary from 21 letters in Finnish to
38 in Czech. Extensive alphabets are a handicap in the modern world
because they make keyboarding difficult. Therefore governments have
sought to prune unwieldy alphabets and eliminate redundant
characters. (After the Russian Revolution, the Soviets cut the
Russian Cyrillic alphabet from 36 to 32 letters.) Serious efforts
have also been made to simplify non-alphabetic languages, such as
Japanese and Chinese, to permit them to be written (and keyboarded)
more easily.
Since written languages are vehicles of communication, they possess
statistical similarities as information-carrying alphabetic codes.
Individual letters appear with varying frequencies, because it is a
fundamental principle of information theory that a random sequence
of characters cannot contain any information. (A random sequence
may be defined as one in which all one-character, two-character, .
. . n-character sequences are equally probable.)
When characters are ranked in the order of their occurrence, their
relative frequency in various languages is quite similar. This
uniformity increases for languages possessing a common alphabetic
and linguistic ancestry. The Romance and Germanic languages are
important examples; they use the Roman alphabet and share a common
Indo-European origin.
About a third of the letters in these languages occur often. The
remainder appear with decreasing frequency, concluding with a set
that rarely occur. In English, the space and four commonest vowels
(a, e, i, and o) account for 42% of the characters. Another 29% are
represented by the five commonest consonants (n, r, s, t, and h).
In contrast, the five rarest consonants (j, k, q, x, and z) account
for less than 1% of the text.
Leading characters in European languages possess a similar
frequency distribution. Table 1 records the individual frequencies
of the space and five commonest vowels in English, German, French,
Italian, Spanish, and Portuguese. Table 2 lists the individual
frequencies of the six commonest consonants in these languages.
Table 3 records the cumulative frequencies of the space and four
commonest vowels, the five commonest consonants, and the ten
commonest characters in these languages. (These tables and later
ones disregard the numbers and punctuation marks that make up about
3% of ordinary texts, as well as diacritical marks.)
Although vowels appear more often in Romance languages (French,
Italian, Spanish, and Portuguese) than in Germanic ones (English,
German, Dutch, and Swedish), the cumulative frequency distribution
of ranked characters is similar in major European languages.
According to Table 3, the ten commonest characters (which usually
lie directly under the fingers on optimum keyboards) account for
about three out of four characters. This uniformity exists despite
differences in the size of the alphabet in these languages.
This regularity persists even for languages represented by syllabic
rather than alphabetic symbols. Thus the 48 kana, which transcribe
Japanese phonetically, possess a ranked frequency distribution that
is comparable to the ranked letter distribution in European
languages (when a correction is made for the larger number of
kana).
Characters carry more information when they appear with varying
frequency. Since written languages have evolved as efficient means
of communication, their word lengths and letter frequencies are
distributed to facilitate transmission of information. The space is
almost always the most frequent character because the commonest
words are invariably short monosyllables that are easy to speak and
write. (The 50 commonest words in English, which account for 40% of
the words in typical texts, are all monosyllables.)
Although the cumulative frequency distribution of ranked characters
is substantially the same in major European languages, the rank of
individual letters vary from language to language. Table 4 lists
the maximum and minimum frequencies of individual letters (ignoring
spaces) in nine languages. The table reveals the substantial spread
between these maximum and minimum frequencies. The e amounts to
19.3% of the letters in Dutch, but only 10.2% in Swedish. The o
represents 11.5% of the letters in Portuguese, but only 2.1% in
Dutch; the d is 6.4% in Danish, but 3.4% in French. Likewise, the i
accounts for 11.3% in Italian, but only 5.7% in Swedish; the h
occupies 5.6% of the text in English, but only 0.7% in Spanish.
In addition to these wide differences, some letters are common in
certain languages, but virtually absent in others. The y appears
more than once in every hundred letters in English and Spanish, but
is extremely rare in German, Italian, and Portuguese. The w occurs
an average of once in every seventy letters in English and German,
but less than once per thousand in French, Spanish, and Italian.
LIkewise, the q appears about once in every hundred letters in
French and Spanish, but hardly ever occurs in English, German, or
Swedish.
Because of these wide variations, the letter arrangement on optimum
keyboards will be diffeent in each language. This conclusion is
reinforced because vowel-vowel and consonant-consonant digraphs
must be considered, as well as individual letter frequencies in
minimizing stroking motions. These two-letter combinations yield
several hundred additional frequencies which, when added to
individual letter frequencies, furnish each language with a unique
statistical profile.
This profile assigns unique frequencies to one and two-letter
combinations. When these frequencies are ranked in numerical order,
an underlying similarity emerges connecting various European
languages. This similarity insures that the distribution of finger
motions on the optimum keyboards of this invention will resemble
each other, even though specific strokes produce different letters.
In particular, the proportion of alternate-hand and home-key
strokes will exhibit similarities in Various European languages. As
a result, principles of keyboard design developed for one language
may be applied to other languages--and numerical methods of
analyzing finger motions may be carried over from one language to
another.
Digraph frequencies determine the optimum letter arrangement. These
frequencies, however, cannot be derived from single-character
values because successive letters are not statistically
independent. The probability of a pair of letters appearing depends
on their order. (In English, the digraphs th, nd, and ea are far
more probable than the reverse digraphs ht, dn, and ae.) Phonetic
constraints favor alternating vowels and consonants, rather than
successive consonants or vowels. Linguistic rules also bar certain
combinations as admissible words. (In English, a u always follows a
q, but a q never follows a b, f, or t.)
According to Shannon's pioneering study of the information content
of written English [Bell System Technical Journal, vol. 27 (1948),
p. 379], letter sequences in natural texts may be assumed to be
generated stochastically (by chance). As a first approximation
character sequences may be assumed to be governed by a Markov
process in which the likelihood of a character appearing is given
by the transition probability linking a character and its immediate
predecessor. (These transition probabilities may be obtained from a
table of digraph frequencies by dividing individual digraph
frequencies by the number of digraphs in which the second character
appears.)
The Markov hypothesis is a useful first approximateion because it
excludes forbidden letter sequences and takes account of
correlations between adjacent characters. It assumes, however, that
the probability of letters occurring depends on only the preceding
character. This hypothesis is violated in most languages for
sequences involving three successive vowels (vowel trigraphs), or
three successive consonants (consonant trigraphs), because the
probability of these sequences is sharply reduced by the
predominant alteration of vowel and consonant phonemes (sounds).
Since phonemes are usually represented by one or two letters (such
as n, th, ch, and ng in English), most consonant and vowel
trigraphs are formed by a union of monosyllabic roots containing
initial and terminal consonants, or vowels (as in inch, control,
and impress).
The relative absence of vowel and consonant trigraphs is important
in keyboard design. Placing vowels and consonants on opposite sides
of the keyboard curbs triple strokes by the same hand by reducing
the number of one-hand trigraphs. For English and the Romance
languages, a majority of these trigraphs may be processed by a
chord and a home-key stroke, so that only chordless trigraphs
present difficulties. But these trigraphs are so rare, they can be
ignored.
The practical absence of trigraphs requiring three strokes by the
same hand, which might be predicted on linguistic grounds, has been
verified for the English language by a computer count of one
million words. This count proves that grouping vowels and
consonants on opposite sides of the keyboard greatly simplifies
stroking motions by reducing the number of one-hand trigraphs to
one-eighth their value on the standard keyboard. Similar
conclusions hold for the Romance languages. More consonant
trigraphs appear in Germanic languages (German, Dutch, and Swedish)
because of the ease with which they compound monosyllables to form
polysyllabic words. However, a judicious arrangement of letters
combined with chording can diminish the effect these trigraphs on
overall processing rates.
Due to the relative absence of one-hand trigraphs, only one-hand
digraphs need by considered in developing optimum keyboards. The
distribution of these digraphs can be determined by counting the
frequency with which pairs of characters appear in representative
texts. Single letter frequencies may be obtained by summing the
digraphs in which a specific letter appears in either an initial or
final position.
Only letters and spaced need by included in the diagraph table.
Digits, which account of for about 1 % of the characters in
ordinary texts, may be disregarded because they appear as
independent linguistic entities, separated by spaces from other
words, and are customarily assigned a separate row or bank of keys.
Puntuation marks may also be omitted because they are governed by
editorial convention, rather than intrinsic properties of the
language. Thus the amount of punctuation has dropped sharply in
English during the last sixty years without a corresponding change
in the language itself. Since punctuation marks are attached to the
ends of words (period, comma, hyphen), or at well-defined points
within words, (the apostrophe), their intersection with other
letters may be ascertained from letter and space digraph
frequencies.
The location of the period and comma keys on the vowel side of the
keyboard is significant because they appear nearly once in every
hundred characters. Optimum placement requires a knowledge of the
frequency with which these punctuation marks are preceded by
specific vowels. This information, however, may be determined with
sufficient accuracy from vowel-space digraphs.
Digraph frequencies are obtained by tabulating successive
characters in a sample text. If these values are to apply to the
language in general, the sample must be representative of the
entire language and include enough characters so that statistical
flucatuations may be neglected. If the sample is biased, observed
frequencies will depart systematically from population values,
since common words will occur too often (or too rarely). For
instance, samples drawn from works of fiction, or business and
personal correspondence, contain a much higher proportion of
personal pronouns than extracts from scientific papers or
government reports. Similarly, extracts from learned and technical
writing include longer words and fewer spaces than samples from
colloquial sources. if telegraphic texts are used, which is the
practice in cryptography, the letter h will appear only 60% as
often as in ordinary English prose, because of the absence of such
common words as the, that, this, he, and his from telegrams.
Drawing extracts from a variety of genres decreases the likelihood
of sampling errors due to an eccentric distribution of words.
Sampling errors will effect only a limited number of digraphs; they
will not influence keyboard design if they consist of alternating
vowel-consonant pairs, since design depends on one-hand digraphs
(consonant-consonant, vowel-vowel pairs). Consequently the letter
arrangement on the optimum keyboards of this invention are not
sensitive to sampling variations.
In determining digraph frequencies, the sample must be large enough
so that statistical fluctuations due to the finite sample size may
be neglected. Since digraphs are sampled from a multinomial
distribution, the standard deviation of individual digraph
frequencies will vary as the square root of their observed
frequency--and the standard deviation of their probability will
vary inversely with the square root of their observed
frequency.
Digraph frequencies of interest range from several per cent down to
one per thousand (the lower limit is somewhat arbitrary, since it
represents the frequency below which specific stroking motions can
be ignored). Common digraphs containing characters directly under
the fingers, which determine the arrangement of home keys, average
a fraction of 1%. For keyboard design, the relative rank of
differeent stroking motions is required rather than their absolute
values. Therefore a sample of 100,000 characters is sufficient to
reduce statistical fluctations to acceptable levels. With this
sample size, an observed digraph frequency of 400 has a standard
deviation of 20, and the standard deviation of its probability is
5%.
A much larger sample is necessary to evaluate the importance of
specific trigraphs because they occur with lower frequency. Since
significant one-hand trigraphs appear from three to five times less
frequently than corresponding digraphs, a sample of one to two
million characters is needed to obtain reliable data on particular
trigraphs. The tabulation of these trigraphs is simplified, since
only combinations occurring entirely on the consonant or vowel side
of the keyboard need be included. A much smaller sample is
sufficient, however, to determine the cumulative fraction of
one-hand digraphs or trigraphs in a given language.
Digraph Table for the English Language
Because of its importance, a large sample has been used in
compiling the digraph table for the English language (Table 5). The
sample consists of a one million words containing 5.7 million
characters (letters and spaces). The sample is composed of 500
selections of contemporary American English, each approximately
2,000 words long. These extracts have been taken from newspapers,
magazines, biographies, belle-lettres, learned and scientific
writing, in addition to various forms of fiction (to simulate
letter frequencies occurring in personal and business
correspondence). Strictly speaking the digraph table refers to
American English. However, it can be used for British English
because differences due to British usage and spelling are
negligible as far as keyboard design is concerned.
In Table 5, the space is represented by a hyphen. The recorded
values are based on a sample of 5.7 million characters, normalized
to 100,000 characters and rounded off to the nearest integer.
(Rounding errors explain why row and column totals differ from each
other, and from the totals at the bottom of the table recording the
frequency of individual characters.
Keyboard Design
This invention describes a systematic procedure of designing an
optimum keyboard in any alphabetic language that can be keyboarded.
The method employs kinesthetic principles and a statistical count
of two-character combinations to determine a letter arrangement
that minimizes finger movement and reduces input to a small set of
independent stroking motions. The procedure is described in detail
for the English language to indicate how the method is applied to
other languages, which will be discussed later. Definite reasons
govern the location of every character on the keyboard. For
English, each character is in a different position than on the
standard keyboard.
Grouping vowels and consonants on opposite sides of the keyboard is
a fundamental element of this invention. Vowels, (diacritical
marks), rare consonants, and puntautaion marks are set on the left
side of the keyboard; the remaining consonants on the right side.
Four high frequency vowels and the space key are placed directly
under the fingers of the left hand--and five high frequency
consonants directly under the fingers of the right hand. For most
European languages, the home-key characters are the ten commonest
characters in the language, accounting for about three out of four
of the letters and spaces in representative texts. These high
frequency characters lead to automatic touch typing, since most
strokes are made on home keys hidden from view.
Vowels and consonants may be identified from a digraph table by the
way they combine with other letters. Vowels consist of a small
group of letters that combine often with a larger set of letters
(consonants), but rarely with themselves. Similarly, consonants
appear often with nearly all vowels, but with only a limited set of
consonants.
The procedure of grouping letters on opposite sides of the keyboard
may can be applied in languages, such as Hebrew and Arabic, that
omit vowels from their written language. In this case, consonants
may be divided into two groups, composed of letters that tend not
to combine with each other. Segregating these letters on the
keyboard minimizes the number of one-hand strokes, and succeeds in
any language whose characters transmit information, since its
character sequences must exhibit statistical regularities.
Letters are arranged on optimum keyboards according to their
frequency. Common letters appear on home keys directly under the
fingers; letters with middle frequencies on adjacent keys; and rare
characters at the extremities of the keyboard. When two keys
outside the home position are assigned to the same finger, the
character occurring more often is set closer to the home
position.
Distributing characters according to their frequency minimizes
substitution errors produced when the same finger operates keys of
comparable frequency. An example occurs on the standard keyboard,
where the common consonants r and t, lie side by side. These
letters are often mistakenly substituted for each other because
they they are both stroked by the fourth finger of the left hand.
Such sustitution errors are reduced on the optimum keyboards of
this invention because characters are alloted to the same finger
differ sharply in frequency.
Common letters are assigned to the home keys. The next group are on
the thumb and home rows in the center of the keyboard, alloted to
the thumb and fourth finger, respectively, because these keys are
easiest to stroke outside the home position. To minimize successive
strikes by the same finger, characters assigned to the same finger
are chosen so they rarely form digraphs together. Letters are
arranged on different rows so that important digraphs can be
readily executed. To lighten the stroking load on the little
finger, low frequency letters are placed on keys operated by the
little finger. When a diacritical mark appears with several letters
in foreign languages, each diacritical mark is alloted to an
individual dead key that generates the diacritical mark, but does
not advance the system in the horizontal direction. This reduces
the number of separate keys that must be learned.
Characters on home keys are distributed so that major digraphs may
be stroked by adjacent fingers, or by the thumb and another finger.
These letters are arranged so common digraphs may be stroked
serially on the same row in motions from the little finger to the
fourth finger, or a thumb stroke followed by another finger stroke.
Such movements suit the architecture of the hand, and are easier to
complete the sequences in the opposite direction.
Since common letters lie under the fingers, home keys on the
ten-finger keyboard in English, German, French, Italian, and
Portuguese are essentially determined by the vowel and consonant
frequencies given in Table 1 and 2. In English, Italian, Spanish,
and Portuguese, the four vowels lying under the fingers of the left
hand are a, e, i, and o. In German and French, the u replaces the o
as one of the vowels under the fingers of the left hand. In English
and German, the five consonants under the right hand are n, r, s,
t, and h. In French and Italian, the l replaces the h; and in
Spanish and Portuguese, the d replaces the h as a home key.
The consonant with the largest number of substantial one-hand
digraphs is assigned to the thumb key, since the thumb has the
greatest kinesthetic independence. The choice of vowels and
consonants on home keys is straightforward when the four commonest
vowels and the five commonest consonants appear much more often
than other vowels and consonants, respectively. When other letters
have comparable frequencies, the letters selected for the home keys
possess the largest number of significant one-hand digraphs,
particularly with other home keys to permit rapid entry of common
digraphs. This is the reason that the t is chosen as a home-key in
Spanish rather the the l or c, and the t as a home character in
Portuguese instead of the m, although the l, c, and m occur with a
similar or greater frequency.
In general, the number of letters with a similar frequency is
limited because languages are information-bearing alphabetic codes
whose letters appear with varying frequency. The choice of home-key
letters if evident in English because the four commonest vowels and
the five commonest consonants appear much more often than othe
vowels and consonants. The i (6.0%) occurs more frequently than the
u (2.2%); the h (4.8%), more often than either the l (3.4%) or the
d (3.3%). This choice of home keys is confirmed gy comparing
one-hand digraphs. The i has two significant digraphs, space-(1187)
and io (447); but the u has only one, ou (634), which may be
produced by a chord. Likewise the h has three substantial digraphs,
th (2337), ch (378), and wh (258); but the l and d appear in one
each: ld (202) and nd (851), and nd may be replaced by a chord. (In
this paragraph and subsequent paragraphs, percentages in
parentheses refer to the frequencies of individual letters
including the space. (The numbers in parentheses following digraphs
record their occurrence per 100,000 letters and spaces, as given in
Table 5.
Since n appears as the initial letter in the common digraphs: nc
(244), nd (851), ng (664), ns (294) and nt (618); the n is set
under the right thumb. The location of the space key under the
opposite thumb is confirmed by the substantial digraphs: e-space
(3524), space-a (2010), space-i (1187), and space-o (1248).
The commonest consonant, t (7.6% ), is placed under the third
finger. It is flanked by the h and s to permit speedy entry of th
(2337) and st (720). The h is assigned to the fourth finger because
the h rarely combines with the other consonants in the center of
the keyboard. Finally, the r is alloted to the little finger for
quick input of rs (270) by the little and second fingers.
On the vowel side of the keyboard, the commonest vowel, e (10.3%),
is set under the third finger. The a is under the fourth finger for
swift stroking of ea (474); and the i and o lie side by side for
easy input of io (447).
To lighten the stroking load on the little finger, the y is placed
at the outer end of the vowel home row because it is the final
letter in 70% of the words in which it appears. The g is set at the
outer end of the consonant home row because it is preceded by the n
in 40% of the words in which it occurs. Chording the digraph
y-space and ng sharply reduces movement of the little finger to
strike tye y or g.
Since letters are arranged to minimize successive strokes by the
same finger, the i is assigned to the little finger on the home
row, since it rarely combines with the y. This in turn fixes the o
under the second finger. The u is set on the thumb row. Alloting
the fifth vowel to the thumb facilitates learning by identifying a
different vowel with each finger. In addition, it reduces
substitution errors produced when two common vowels are assigned to
the fourth finger in the center of the keyboard.
Since the letter u rarely begins or ends a word in English,
successive strikes by the thumb are limited. The carriage return is
on the thumb row next to the space key because it replaces the the
space at the end of each line. Since the u (2.2%) occurs more often
than the carriage return (1.7%), the u is assigned to the flexed
thumb key in the center of the keyboard, and the carriage return to
the extended thumb key at the outer end of the thumb row, because
the flexed key is easier to operate than the extended thumb
key.
The high frequency consonants d and l are set on the end of the
home row and the thumb row, respectively, because the d rarely
combines with the h, and the l seldom joins with the n. Medium
frequency consonants are placed on the top letter row opperated by
the second, third, and fourth fingers. The c (2.6%), m (2.1%), and
the f (1.9%) are alloted to the second, third, and fourth fingers,
respectively, because they rarely combine with the s, t, and h
operated by the same fingers. This arrangement permits easy entry
of the digraphs ct (237) and fr (137).
Other letters are distributed in a similar fashion. The p (1.7%) is
alloted to the fourth finger on the lower letter row because it
rarely combines with h, d, or f. This location also enables the
digraphs pr (268), pl (166), and mp (136) to be stroked readily.
Similarly, the w (1.5%) is set on the thumb row because it seldom
appears with the l or the n. This allows the digraph wh (258) to be
easily stroked by the thumb and fourth finger. The b (1.3%) and the
v (0.8%) are assigned to the little finger because they occur
infrequently. The b is on the upper letter row so the digraph bl
(155) can be executed by straightening the little finger and
flexing the thumb.
The principles used in arranging letters on the consonant side of
the keyboard can be applied to rare consonants on the opposite side
of the keyboard. Since the digraph ex (122) occurs in four out of
five words in which the x appears, the x is assigned to the second
finger on the upper letter row to expedite stroking this digraph.
Likewise, since ju (43) appears in two out five words in which the
j appears, the j is set on the lower letter row, so ju can be
stroked by moving the little finger and the thumb toward each
other. The question mark is assigned to the little finger because
it appears infrequently, and the z is set on the lower letter row
next to the vowels to assist in stroking combinations involving the
z and vowels.
Major punctuation marks (period, comma, hyphen) are alloted to the
strong fourth finger in the center of the keyboard. This choice
minimizes successive strikes by the fourth finger because these
punctuation marks rarely follow the letter a. It also permits the
common sequences e-comma and e-period to be executed swiftly by the
third and fourth fingers. Since one word in six ends in e, the
shift key is set on the upper letter row over the e to prevent the
third finger from having to make two successive strokes when keys
are individually operated. This isolation succeeds because a space
or a tab precedes a shift. Furthermore, when keys are serially
operated, the sequences (punctuation, space) and (hyphen, carriage
return) may be executed by a simple kinesthetic motion.
Substitution errors are minimized by setting rare characters at the
extremities of the keyboard. The k (0.5%) is at the edge of the
keyboard operated by the fourth finger of the right hand, next to
the f (1.9%), which appears four times more often. Similar adjacent
key-pairs containing characters of widely differing frequency
include on the left hand: (one, slash), (question mark, colon), and
(period, hyphen)--and on the right hand: (p, q), (b, double
quotation mark), and (zero, one-half).
The principle of maximizing alternate hand movements restricts the
location of certain keys. The tab is assigned to the right thumb
because it usually follows a carriage return stroked by the
opposite thumb. The q (0.1%) is set on the consonant side of the
keyboard because it is followed by a u. The apostrophe is set with
the vowels, since it appears either between consonants in
contractions (as in it's, don't, and can't), or before the s in
possessives. Double quotation marks are grouped with consonants
because they generaly precede a shift stroke in opening a
quotation--and normally follow a comma, period, or question mark in
closing a quotation.
The space and back space keys are on opposite thumbs to facilitate
moving the system to and fro horizontally. Placing controls with
related functions, or symbols resembling each other, on opposite
hands eliminates the motor confusion that occurs when they are
alloted to the same finger, or the same hand. For this reason, open
and close brackets are set at the opposite ends of the number row,
and open and close parentheses at the opposite ends of top letter
row to symbolically enclose their respective key rows.
Since parentheses are often used in contemporary English prose to
mark off parenthetical clauses and sentences, these symbols are
placed on the top letter row. This row contains twelve keys,
instead of the eleven on the standard keyboard. The introduction of
an additional key on the top letter row allows the colon to be
given a lowercase position under one parenthesis--and the double
quotation marks to be set under the other parenthesis. The
semi-colon is assigned to an upper-case position over the question
mark because it is much rarer than the colon. Likewise, the
exclamation point is set in the upper-case position over the
apostrophe because it is very rare.
Associative learning is accelerated by arranging characters so they
can be readily associated with specific hands. This technique,
which has been employed on the letter rows by dividing the keyboard
into vowel and consonant sides, is utilized on the number row by
alloting odd digits to the left hand, and even ones to the right
hand. These numbers are arranged in serial order from left to
right: 1, 3, 5, 7, 9 . . . 2, 4, 6, 8, 0. The zero is next to the
eight, so fingers operating the zero and one keys will be
responsible for a single digit each. This is desirable because the
zero and one appear twice as often as other digits. The slash and
the one-half keys are at the outer ends of the number row because
both symbols usually appear with other digits. The one-half key is
placed next to the zero key, instead of the one key to prevent the
one and the one-half keys from being erronesouly interchanged.
Splitting the number row into even and odd sequences permits digits
to be entered by a two-step associative process. The first step
identifies a digit with a specific hand--the second step, with a
specific finger. Since even and odd is a concept that has been
instilled in individuals since childhood, students can associate
the left hand with odd digits more readily than with the numbers
one through five, and even digits more readily with the right hand
than with the numbers six through zero. Retaining the serial order
of digits on each side of the number row makes it easier to learn
the location of specific digits--and leads to faster entry of
numerical data when mixed visual and touch typing is employed by
reducing the visual field that must be scanned.
The "pipe-organ" method may be fruitfully employed for numerical
input. In this method, the hands are shifted from the home row to
the upper letter row, so the fingers are in contact with the
vertically oriented number keys, which serve as a new set of home
keys. Numerical data can be inputed accurately by moving the hands
from one row to another, like a musician playing an organ, instead
of reaching for number keys across the top letter row while holding
hands stationary on the home row. The hands can be shifted quickly
back and forth because the keys in different rows lie in straight
lines above each other and the contoured keyboard supplies helpful
tactile cues to guide the hands to home position.
Since control keys are located in the center of the keyboard,
fingers can remain in contact with the vertically oriented number
keys, while thumbs operate the space, tab, and carriage return
keys. The period needed to enter decimals, and dollars and cents
can be stroked easily because the period and shift keys are on the
top letter row. The pipe-organ method is particularly effective in
processing numerical data in tabular form because fingers can rest
against the number row while thumbs rest on the tab and carriage
return keys. This is impossible on the standard keyboard where the
right hand must be removed from the number row to strike the period
and carriage return keys. Furthermore shifting the hands between
the home row and number row is awkward on the standard keyboard
because the keys are staggered on different rows, and there is no
tactile cues to guide the fingers to the home position.
The Programmed Keyboard
The keyboards of this invention are designed to permit the use of
programmed instructions in response to single key or chord strokes
when the keyboard is attached to sophisticated devices, such as
electronic typewriters, word processing machines, CRT terminals,
and computer input stations, whose electronic circuity can convert
key strokes into a desired output. Such circuity simplifies the
entry of alphabetic information by replacing repetitive sequences
executed by human operators by machine instructions.
ON the programmed keyboards of this invention, a single stroke
produces the characters needed to go from one sentence to another--
and a single chord generates the strokes required to go from one
paragraph to another. Common one-hand digraphs are produced by
simultaneously striking pairs of home keys. Programming also
eliminates the necessity of operating the carriage return at the
end of each line.
Although most keyboards are controlled electrically or
electronically, it is still usually necessary to hold down the
shift key to input upper-case characters. This slow, time-consuming
method of entering capitals is a legacy from the manual typewriter.
Generating an upper-case character entrails two separate actions:
shifting to the upper case--then releasing the shift to return the
system to the lower case. Learning to enter capitals on the
standard keyboard demands extensive practice because each capital
must be associated with one of the two shift keys at the corners of
the keyboard, which must be operated by an awkward motion of the
little finger.
These obstacles are absent on the keyboards of this invention which
use only one shift key (assigned to the third finger of the left
hand, except for German). This shift key acts on a single character
and automatically returns the system to lower-case operation after
an upper-case character is produced. This allows the shift and
upper-case character keys to be stroked serially. (A shift key
acting on a single character is effective because a lower-case
character nearly always follows an upper-case character. (An
exception occurs in Spanish where sentences may begin with an
inverted question mark or an inverted exclamation point.) Since
most capitals are consonants, the shift key is located on the vowel
side of the keyboard. This in turn indicates that common symbols on
the number row ($, %, =) should be set on the consonant side of the
keyboard, so they can be entered by a pair of alternate-hand
strokes.
Capitals may be rapidly inputed because there is only one shift
key, and the sequence (space, shift) can be easily executed by the
thumb and third finger of the left hand. This is a marked asset in
processing newspaper and magazine texts, which contain a host of
capitals due to the prevalence of personal, place, and
organizational names in journalistic copy.
The letter arrangements presented herein allow upper-case
characters to be generated on electric typewriters using a single
shift key. If this shift disengages after each stroke, serial
stroking can be employed. If a conventional shift key is retained,
the third finger can hold down the shift key while another finger
strikes the upper-case character key. When this key would be
normally struck by the third finger of the left hand (the e or five
key in English), the third and fourth finger can operate the
required keys.
On the programmed keyboards of this invention, a single stroke
replaces the fixed sequence of strokes occurring after certain
punctuation marks, such as the transition from one sentence to
another, which usually requires a period, two spaces, and a shift.
These four strokes are generated automatically by a lower-case
period-- eliminating three superfluous strokes. The period needed
to input decimals and abbreviations are produced by an upper-case
period, which is easily stroked as a digraph, since the shift and
period lie side by side on the top letter row.
Operating the lower-case comma, colon, or semi-colon keys
automatically generates a space following a comma, colon, or
semi-colon, respectively. The comma needed in numbers and
quotations is produced by an upper-case comma, or by stroking the
back space key, which can also delete the space after a colon or a
semi-colon.
A single chord stroke replaces the fixed sequence of strokes needed
to go from one paragraph to another. The key-pair (shift, period)
executed by the third and fourth finger generates the output
(period, carriage return, tab, and shift). This chord may be
readily stroked because the shift and period keys lie side by side
on the top letter row. Passing from one pargraph to another in a
single stroke is particularly helpful in processing newspaper copy
where paragraphs are often only one or two sentences long.
A different chord generates the sequence (period, two carriage
returns, and a shift) needed to pass from one paragraph to another
in single-spaced business letters. This sequence is produced by the
chord (shift, question mark) executed by the second and third
fingers.
A programmed keyboard can eliminate the need to operate the
carriage return key at the end of each line. Such programming is
now incorporated in cathode ray terminals which automatically
transfer words to the next line of the screen when they terminate
beyond the end of a line (wrap-around). On word processing
equipment, an analogous procedure is employed when the text is
played out in the "adjust mode." When either a space or a hyphen is
sensed within a given number of spaces from the end of a line (the
hot zone), the machine interprets a space as a carriage return, and
generates a carriage return after a hyphen.
A similar procedure is adopted on the programmed keyboards of this
invention. When a space or hyphen key is struck within a given
number of spaces from the end of a line (which may be varied), the
machine automatically generates a carriage return. This eliminates
the necessity of moving the thumb from its home home position to
strike the carriage return key, which occurs about every 60 to 75
characters. It also allows operators to input the text without
worrying about reaching the end of a line. This automatic carriage
return may be eliminated by striking the margin release key to
permit input beyond the hot zone.
Characters may be stored internally in the machine (rollover) and
played out after the system has passed from the end of one line to
the beginning of the next one. This avoids the danger of losing
characters while the system is changing lines, and permits
operators to continue keyboarding while the machine is shifting
lines. Internal character storage, which is often employed on
electronic keyboards, enables a chord to be entered by one hand
while the machine is processing a previous chord stroked by the
opposite hand. Since each chord produces two or more characters,
internal storage allows input to approach the maximum machine
output when these rates are comparable.
Chording
A majority of the one-hand digraphs on the keyboards of this
invention involve characters lying directly under the fingers. Many
of these digraphs can be processed efficiently by chord strokes in
which two keys under the fingers are operated simultaneously.
Although cord stroking has been used for a long time in
stenographic machines, telegraphic terminals, and chord typewriters
to reduce the number of keys needed to generate a given set of
characters, the keyboards of this invention employ chords that can
be learned far more readily because their output coincides with the
output of the same keys operated serially in a majority of
cases.
The method of converting chords into multiple characters will
depend on the device attached to the keyboard. It will be different
for an electronic typewriter, a CRT terminal, a paper tape
perforator, or a computer input station recording data on magnetic
tape or disks. Since the output of individual chords is closely
related to the keys simultaneously stroked, chording may be readily
introduced in equipment containing sold-state electronic
components. It can also be added to devices originally designed for
single stroke operation.
The two-key chords used in this invention are based on a
statistical analysis of letter frequencies that minimize successive
strokes by the same hand and combine the ease of chording with the
speed of alternate-hand stroking. Eight easy chords are employed
involving a pair of keys lying under the fingers of each hand. They
are: simultaneous operation of the thumb key and a home row key
(four strokes); simultaneous operation of two adjacent keys on the
home row (three strokes); and simultaneous operation of keys under
the little and fourth fingers (one stroke). Experimental
measurements show that these eight two-finger chords may be
executed quickly and accurately. (Additional three-finger chords
may be added for languages, such as German, to input common
three-character sequences.)
These chords may be completed by a single movement of the hands
almost as rapidly as a single stroke. Since a chord usually
generates two characters, each chord effectively eliminates one of
the strokes required when keys are operated sequentially. When
chording is used, the keyboard must be buffered, however, to
introduce a time delay that will enable the machine to determine
whether a pair of strokes should be interpreted as a chord, or as a
pair of individual strokes. This time delay will not reduce the
output rate when characters are stored internally, as long as the
sum of the delay time and the output time is less than the mean
character input time. Thus the output time on an electronic
typewriter might be .03 sec. (corresponding to 33 characters a
second) and the delay time .01 sec. Their sum, .04 sec., fixes the
maximum through-put rate at 25 characters a second, or 250
six-character words a minute. Internal storage is thereof important
in achieving maximum processing rates--especially when chording is
used, and keyboard input and machine through-put rates are
comparable.
Double letters form a significant class of one-hand digraphs,
accounting for 1.7% of the letters and spaces in English. The
commonest repeated letters are 11, ee, oo, ss, and tt. On
conventional keyboards, these double letters cannot be produced
quickly because repeated strokes by the same finger require more
time than strokes by alternate hands. On programmed keyboards,
double letters may be entered rapidly by holding down the
corresponding letter keys to instruct the machine to generate the
double letters. This procedure leads to faster input because the
time that a key must be depressed is much shorter than the time
required to complete a double stroke. Holding a key down is much
simpler kinesthetically than making a repeated stroke on the same
key, particularly for double letters lying outside the home
position, such as 11, pp, and ff. Consequently double letters can
be processed more efficiently on programmed keyboards than on
conventional keyboards. Generating double letters automatically is
a valuable asset in foreign languages where repeated letters are
common. Examples include Dutch which has many double vowels, and
Swedish which has many double consonants.
Operators can switfly learn to produce repeated letters by holding
down a letter key because of the ease of associating double letters
with an extended key stroke. Only a limited group of double letter
combinations must practiced to learn the method, since the same
general motor response applies to all repeated letters. This is
analogous to learning the shift key, where only a small set of
capitals must be practiced to master the method. since automatic
input or repeated letters is easy to learn, this feature is applied
to the entire alphabet. (A possible exception is the x, which may
be made to repeat as long as the x key is held down.)
Double letters occur often enough in typical English texts to
reinforce initial learning of the extended stroking response. As a
result, rapid entry will be maintained after early training because
of the prevalence of repeated letters. Employing an extended stroke
to generate double letters significantly reduces the number of
successive strokes that must be made on keys outside the home
position, and is a natural extension of chording in which a pair of
keys are struck simultaneously to produce a digraph consisting of
two different characters.
The output of particular key-pairs is determined by the digraph
frequencies in the language. A small number of common one-hand
digraphs are obvious candidates for chording. Most of these
digraphs involve characters on the home keys, since they appear
more often than the letters on other keys. The assignment of
particular digraphs to specific key-pairs of straightforward in
most alphabetic languages because the appearance of vowel-pairs and
consonant-pairs differ sharply depending on their order. This is
expected on linguistic grounds, since vowels and consonants
represent phonemes (sounds) that are usually associated with
initial or terminal positions.
The choice of digraphs associated with particular chords may be
illustrated using English as an example. To make the selection
process clearer, the frequencies of individual digraphs per 100,000
letters and spaces (taken from Table 5) are listed after each
digraph.
On the vowel side of the keyboard, half the chords involve the
space and a home-key vowel. The key-pair (e, space) produces space
then e (3524); (space, a) produces space then a (2010); (space, i)
produces space then i (1187); (space, o) produces space then o
(1248). In addition, the key-pair (i, o) generates io (447); and
(e, a) generates ea (472). Since oe (29) and eo (42) rarely occur,
the digraph ou (634) is assigned to the chord (o, e). This
eliminates the need to move the thumb from the home position to
strike the u in ou, and simplifies inputing the common word you.
Since the digraph y-space (1027) appears much more often than ia
(106) and ai (230), y-space is alloted to the chord (i, a). This
reduces motion of the little finger to input this digraph, since
the y ends two out of three of the words in which it appears.
Chords on the consonant side of the keyboard are chosen in a
similar fashion. The key-pair (t, h) produces th (2337); (s, t)
produces st (720); (r, s) produces rs (270); (n, t) produces nt
(618); and (n, s) produces ns (294). Since nh (7) and hn (18) are
very rare, the digraph nd (851) is assigned to the key-pair (n, h),
reducing movement of the fourth finger to strike the d. Likewise,
since ng (664) occurs more frequently than rn (107) and nr (6), the
digraph ng is alloted to the chord (n, r). This choice reduces the
need of the little finger to strike the g, since ng appears in two
out of every five words containing a g. Finally, since ch (378)
occurs more often than hr (58) and rh (12), the digraph ch is
assigned to the chord (h, r), reducing the movements of the second
finger to strike the c.
The output of eleven of the sixteen chords can be generated by
serially stroking the two keys involved. In four of the chords, the
output includes one of the keys simultaneously struck. In only one
case is the output completely different from the pair of keys. This
is quite different from stenographic machines and chord typewriters
where there is little relation between single and multiple key
strokes. Because of the large number of arbitrary chord
combinations that must be memorized in these devices, stroking
facility is difficult to acquire. This is not true on the
ten-finger keyboards of this invention where there is a close
connection between chord input and output.
For the English language, the output of eleven of the chords is
identical with the home keys stroked. These chords may be readily
mastered once the home keys have been learned. Since each chord
generates two characters and is produced by simultaneously
operating a pair of keys, each character reinforces the association
between the visual stimulus and the required motor response.
Although the output of four of the sixteen chords includes only one
of the keys stroked, in three of these cases, the other character
is adjacent to the key chorded. In only one instance (y-space), is
the output different from the keys stroked--and here, the y is next
to one of the keys chorded. This close relation between input and
output insures that chords will be mastered easily and lead to
rapid, accurate entry of common one-hand digraphs.
When the output of a chord does not coincide with the keys stroked
separately, two alternate digraphs may be produced by sequentially
operating the same keys. Significant kinesthetic interference does
not occur between chords and serial strokes in English because
digraphs associated with chords appear much more often than those
associated with serial strokes. This may be confirmed by comparing
their respective digraph frequencies. (In the following equations,
the space is represented by a hyphen.)
On the vowel side of the keyboard:
e-/e-= 8, -a/a- = 5, -i/9- = 11, -o/o- = 7.7, io/oi = 8, ea/ae =
80, ou/(oe+eo) = 9, y-/(ia+ai) = 3,
On the consonant side of the keyboard:
th/ht = 23, st/ts = 3.5. rs/sr = 130, nt/tn = 100, ns/sn = 02,
nd/(nh+hn) = 32, ng/(nr+rn) = 6, ch/(nh+rh) = 6,
From these ratios, it is clear that chords occur far more often
than serial strokes on the same home keys. Therefore chord and
serial digraphs will not be mistakenly interchanged, which would
happen if their frequencies were comparable. In only one case, (o
and space), are serial and chord digraphs comparable. This is due
to the appearance of such common serially stroked words as to, no,
and so, along with such common chorded words as of, on, and or. But
even here, the chord occurs nearly twice as often as the serially
stroked sequence.
Chording is an efficient means of processing one-hand digraphs. A
small set of sixteen chords, eight on each hand, generates a
majority of one-hand digraphs in English. These chords, which are
produced by simultaneously operating a pair of home keys, may be
learned once individual key locations have been mastered.
The utility of the ten-finger keyboards of this invention are
significantly extended because they can be used effectively on
serially stroked keyboards, as well as programmed keyboards.
Although each character must be individually stroked on serial
keyboards for devices, such as electric typewriters, the ten-finger
arrangement permits common digraphs to be executed rapidly by
strokes on home keys. Frequent digraphs involving a home thumb
stroke followed by a stroke on the home row include in English a
space followed by a, i, or o; and an n followed by a d, t, s, or q.
Another set of common digraphs can be completed by strokes on
adjacent home keys going from the little finger to the fourth
finger. Examples in English include: io, ea, rs, st, and th.
Numerical Analysis
The distribution of various one-hand strokes may be determined from
the digraph frequencies of the English language recorded in Table
5. This analysis disregards punctuation, numbers, shifts, and
controls, which may account for 5% of the strokes in ordinary
texts. These strokes are omitted because their frequency will vary
widely depending on the nature of the material being processed and
the programming features on the keyboard.
Table 6 lists the percentages of various one-hand strokes. These
figures reveal that grouping vowels and consonants on opposite
sides of the keyboard substantially reduces the proportion of
one-hand motions because of the tendency of vowels and consonants
to alternate. Since half of the characters appearing in typical
texts belong to the left hand and half to the right hand, 25% of
the digraphs would appear on each hand if character-pairs were
randomly distributed. Instead, 15.6% of the digraphs occur on the
left hand, 13.9% on the right hand, and a total of 29.5% on both
hands. This is three-fifths the percentage for a random arrangement
of characters, and confirms the effectiveness of separating vowels
and consonants.
Table 6 lists the percentage of various one-hand strokes. They are
classified into chords (including double letters), and pairs of
successive strokes containing two, one, or no home-key strokes.
Chords on the left hand account for 11.0% (or two-thirds) of the
left hand digraphs, and chords on the right hand for 7.4% (or half)
the righthand digraphs. Thus, while 29.5% of the text will consist
of one-hand digraphs, 18.4% may be executed by chords, and 11.1% by
one-hand strokes, so that 89% of the letters and spaces may be
processed by alternate-hand or chord strokes.
Since each chord generates two characters, chording effectively
eliminates 18.4% of the strokes needed when serial input is
employed. Another 4% are eliminated by automatically generating the
space after a comma and using a single stroke or chord to go from
one sentence or paragraph to another. Thus a programmed keyboard
for the English language requires only four-fifths as many strokes
as a conventional keyboard.
On the ten-finger keyboard, 11.1% of the digraphs must be entered
by successive one-hand strokes, of which 3.9% involve two home-key
strokes; 5.8% one home and one outside stroke; and 1.4%, two
outside strokes. These serial sequences may be readily executed
because letters outside the home position have been arranged so
that significant one-hand combinations are easily stroked. Examples
include digraphs with one outside letter, such as ex, nc, ct, fr,
pr, and wh, and digraphs with two outside letters, such as ld, bl,
pl, and mp.
Although the left hand performs slightly more strokes than the
right hand (when punctuation marks are taken into account), the
greater dexterity of the right hand is utilized by assigning it
more one-hand sequences requiring serial strokes outside the home
position. The right hand executes 3.9% of the digraphs containing
one outside stroke and 1.3% containing two outside strokes; whereas
the left hand is alloted 1.8% of the digraphs that involve one
outside key, and only 0.1% involving two outside keys.
On the ten-finger keyboard, nearly four-fifths of the letters and
spaces (78.1%) are generated by home-key strokes, and a fifth
(21.4%) by keys outside the home position. In contrast, two-thirds
of the strokes (66.9%) on the Dvorak-Dealey keyboard are made on
home keys, and one-third (33.1%) on outside keys. This increase in
outside strokes is understandable because the Dvorak keyboard
possesses only nine home keys (a, o, e, i, and space on the left
hand; and h, t, n, and s on the right hand). On the Dvorak
keyboard, no vowel digraphs and only three common consonant
digraphs (th, nt, and ns) lie on adjacent keys. Furthermore a
number of significant digraphs are awkward to stroke (ct, bl, fr,
gh, and up) because letters are arranged on three staggered key
rows.
The flaws of the standard keyboard are much more important because
this keyboard must be displaced before a new one can take its
place. The universal keyboard may be described as an alphabetical
array of keys split between two hands. The left hand contains the
letters a through g, q through t, and v, x, and z. The right hand
includes the letters h through p, u and y, plus the space key.
Since common vowels and consonants are assigned to both hands,
thousands of English words can be stroked using the fingers of a
single hand. Furthermore, approximately half the digraphs occur on
individual hands which is the proportion that would be expected if
the letters on the keyboard were randomly distributed.
Dvorak and Dealey analyzed the weaknesses of the universal keyboard
in U.S. Pat. No. (2,040,248). They examined successive strokes and
showed that 28% of the digraphs on the keyboard are hard to
execute. However, they restricted their analysis to two-character
sequences.
Three-character sequences on the same hand are even more
illuminating. Three-character combinations (trigraphs) reveal the
presence of host of complex finger motions that impede the
acquistion of keyboard skill. These trigraphs have been counted by
computer for the one-million word sample (containing 5.7 million
characters) used in compiling the digraph frequencies given in
Table 5. These sequences are bounded by spaces at the beginning and
end of words, i.e., they ignore the trigraphs: letter, space,
letter.
These three-character combinations are tabulated as a function of
their appearance. On the standard keyboard, 99 trigraphs occur more
than 40 times per 100,000 characters and comprise 10.1% of the
letters and spaces. An additional 103 trigraphs appear at least 20
times, amounting to 3.1% of the text. A further 126 trigraphs
appear more than ten times, amounting to 1.8% of the letters and
spaces. Thus a total of 328 one-hand trigraphs (bounded by spaces)
account for 15% of the text.
These trigraphs include such common sequences as ate, ter, ere, and
was, as well as a space followed by the frequent prefixes in and
un. Five out of fifty of the commonest words in English (in, on,
no, you, and him) can be stroked by the right hand, along with the
spaces bounding these words. Although particular trigraphs do not
appear often, there are so many on the standard keyboard, they
comprise moer than one-seventh of the letters and spaces in typical
texts. This army of trigraphs is too large to be mastered
individually. Collectively they force the fingers to follow complex
paths paths in processing alphabetic material.
This host of trigraphs mitigates against rapid input and quick
learning. Such kinesthetic barriers are not present on the
keyboards of this invention where the segregation of vowels and
consonants leads to easy stroking sequences. The absence of
difficult finger motions is indicated by the small number of
one-hand trigraphs. These three-character combinations are
tubulated for English as a function of frequency in Table 7. Only
12 one-hand trigraphs appear more than 40 times per 100,000 letters
and spaces, amounting to 1.2% of the text. Another 12 digraphs
occur more than 20 times and account for 0.4% of the text. An
additional 14 appear more than 10 times, amounting to another 0.2%
of the text. Thus a total of 38 trigraphs account for 1.8% of the
letters and spaces. This compares with 328 one-hand trigraphs on
the standard keyboard, comprising 15% of the text.
These statistics prove that assigning vowels and consonants to
opposite hands is a powerful means of reducing triple strokes by
the same hand. If character sequences occurred randomly, one-hand
trigraphs would account for 25% of the text. Instead they account
for less than 3% of the text (when trigraphs across words are
included). This great decrease, which is due to the alternation of
vowel and consonant phonemes, confirms the effectiveness of
separating vowels and consonants on optimum keyboards. Most of the
one-hand trigraphs in English and the Romance languages can be
readily processed, since they usually consist of a home-key stroke
and a digraph that may be chorded (or sequentially stroked on home
keys when chording is not available). Therefore, as far as input
rates are concerned, triple strokes by the same hand may be safely
disregarded.
In English, 10 out of the 38 significant one-hand trigraphs begin
with the letter n, and 8 of these include an initial digraph that
may be chorded. This confirms the choice of n as a thumb key. The
only problem word is you, which includes three vowels and two
spaces stroked by the left hand. Although these five characters
contain three trigraphs that comprise 12% of the one-hand trigraphs
on the ten-finger keyboard, they do not significantly impair the
total processing rate because they contain a chord stroke and
represent only 0.2% of the letters and spaces.
This analysis neglects the trigraphs (letter, space, letter)
occurring across words. Most of these trigraphs, which amount to
less than 1% of the text in English, can be readily entered on the
ten-finger keyboard because they usually consist of a chord
terminating a word (e-space or y-space) followed by a home-key
vowel beginning a word (a, i, or o). Consequently these digraphs do
not hamper input. Since the transition between sentences and
paragaphs has also been simplified, there are not kinesthetic
obstacles to high performance on the ten-finger keyboards of this
invention.
The numerical methods used to analyze stroking patterns in English
may be applied to other languages as well. Such analysis furnishes
an objective, quantitative comparison between competing designs,
and delineates the effectiveness of arranging characters according
to their statistical behavior. It is also helpful in fashioning
effective instruction materials.
Foreign Language Keyboards
The procedure of designing an optimum keyboard for English may be
utilized for other alphabetic languages. Since this method has been
described in detail for English, only salient features will be
noted for German, French, Italian, Spanish, and Portuguese.
These languages employ diacritical marks, which usually accompany
vowels. On the standard keyboard, letters containing diacritical
marks are generally alloted individual keys. (In German, the a, o,
and u are assigned keys, along with the a, o, and u.) Using
separate keys for letters containing diacritical marks increases
the number of key locations that must be learned. Since letters
without diacritical marks are much commoner than those with them,
this practice leads to keyboards with a large number of rare
alphabetic keys which significantly extends the time required to
gain stroking facility.
The foreign keyboards of this invention use "dead" keys for
diacritical marks. These keys include diacritical marks for both
upper and lower-case characters. The keys generate the diacritical
marks, but do not advance the system in the horizontal direction.
Letters with diacritical marks are produced by striking the
corresponding diacritical and letter keys in succession. Upper-case
diacritical keys do not return the system to the lower case, so
that only a single shift is needed to enter an upper-case letter
containing a diacritical mark. Since these marks usually appear
with vowels proceded by a consonant, diacritical marks are placed
on the vowel side of the keyboard, arranged to minimize successive
strokes by the same finger. Thus on the German keyboard, the umlaut
is set on the upper letter row, assigned to the same finger as the
e because the umlaut does not appear with the e.
Employing a separate key for each diacritical mark, rather than one
for each letter-diacritical combination reduces the number of keys
needed to cover the alphabet, particularly in the Romance langages
where many letters contain diacritical marks. A single accent acute
key can generate a, e, o, and i in Spanish and Portuguese. An
single accent grave key can produce a, e, o, and i in Italian; and
a single circumflex key generate a, e, and o in French.
When a diacritical mark appears with only a single letter, such as
n in Spanish and c in French and Portuguese, this letter is
assigned to the same finger as the letter without the diacritical
mark. This furnishes a helpful associative link connecting the two
letters with the same finger, but does not encourage substitution
errors because the two letters appear with widely differing
frequencies.
Using dead keys for the diacritical marks eliminates superfluous
keys because a single diacritical mark may combine with several
letters. Since specific diacritical marks appear with moderate
frequencies (ranging from a fraction of 1% to 2%), diacritical keys
are stroked often enough in typical texts to reinforce initial
learning of these keys. Consequently a large alphabet containing
many letters with diacritical marks does not seriously impair
keyboard performance.
Many European languages contain rare letters that appear only in
words of foreign origin. The k and w are examples in the Romance
languages. While it is desirable to include such letters on foreign
keyboards, they occur so infrequently in representative texts (less
than 0.1%) that they do not influence input rates. Since the
location of these rare letters may be varied without significantly
effecting processing or stroking efficiency, these letters as well
as minor punctuation marks are not shown on the foreign keyboards
of this invention. These omitted letters are k and w in French and
Spanish; k, w, and y in Portuguese; j, q, x, and y in German; and
j, k, w, x, and y in Italian.
Languages belonging to the same linguistic family exhibit
statistical similarities. Thus the full repertory of chords
employed in English is not required in the Romance languages
because they have only a limited number of common one-hand chords.
The Romance languages also have a higher proportion of vowels and
vowel-vowel digraphs than the Germanic and Slavic languages, which
in turn have a larger fraction of consonant-consonant digraphs.
Despite such similarities, each language possesses unique
linguistic features that must be taken into account in designing an
optimum keyboard. Therefore each of the foreign keyboards of this
invention are discussed briefly--focusing on aspects that effect
input rates and the successful application of kinesthetic
principles and linguistic statistics.
Italian: The basic keyboard is shown in FIG. 5 (the rare letters j,
k, w, x, and y are omitted). The i is set between the o and the a
for easy input of the common digraphs io and ia. The s, t, and r
are assigned to the second, third, and fourth fingers of the right
hand for swift entry of st, tr, rt, and str. The c and the h lie
side by side on the upper letter row so the common digraph ch can
be stroked by the third and fourth fingers. Since nine out of ten
words end in vowels, major punctuation marks (period, comma, and
question mark) are placed on the consonant side of the keyboard,
with the period and comma on the ends of the top letter row. On the
vowel side of the keyboard, the accent acute is between the e and a
keys because it appears as e and a; and the apostrophe is on the
top letter row because it occurs frequently as a connective joining
articles and nouns.
Portuguese: The basic keyboard is shown in FIG. 6 (the rare letters
k, w, and y are omitted). The t is chosen as a home key, rather
than the m that occurs as often, because the t appears in the
common digraphs nt and st. The s, t, and r lie side by side to
facilitate input of st, tr, and str. The frequent digraphs ei, oe,
ia, and ao fix the serial arrangement of the vowels from the little
to the fourth fingers as e, o, and a. The diacritical marks, and
are arranged to minimize successive strokes by the same finger. In
particular, the circumflex is assigned to the fourth finger because
it appears in e and o, and the tilde is alloted to the little
finger because it occurs in a.
Spanish: The basic keyboard is shown in FIG. 7 (the rare letters k
and w are omitted). The t is chosen as a home key letter instead of
the l that occurs more often, or the c that has a comparable
frequency, because the t forms more common digraphs with other home
letters, notably nt and st. The i is set between the a and o for
easy stroking of the frequent digraphs ia and io. The y is on the
consonant side of the keyboard because the y usually appears alone
as a monosyllabic word (meaning "and"). The r is selected as the
home-thumb key (rather than the n as in other language) because the
r appears in a large number of digraphs (including pr, br, gr, rd,
and rt). A novel feature in Spanish is the use of the inverted
quesmark and the inverted exclamation point (i) at the beginning of
interrogatory and exclamatory sentences. These upper-case
punctuation marks are placed on the top letter row alongside the
shift key, so they can be produced readily by successively striking
the shift and corresponding punctuation key. Only a single shift
stroke is needed at the beginning of interrogatory and exclamatory
sentences because the inverted question and inverted exclamation
keys do not return the system to lower-case operation.
French: The basic keyboard is shown in FIG. 8 (the rare letters k
and w are omitted). The common digraphs, ai, ie, eu, and ue
determine the serial arrangement of vowels from the little to the
fourth finger as a, i, e, and u. The accent acute is assigned to
the fourth finger because it does not appear with the u, and the
accent grave to the second finger because it does not appear with
the i. Similarly, the circumflex is alloted to the little finger
because it does not occur with the a. On the consonant side of the
keyboard, the p is assigned to the second finger and the c to the
third finger on the upper letter row for simple stroking of the
digraphs pr, ps, cl,and ch.
German: The basic keyboard is shown in FIG. 9 (the rare letters j,
q, x and y are omitted). The vowels a, u, e and i are serially
arranged from the little to the fourth finger for easy entry of the
common digraphs au, ei, and ie. Since all nouns are capitalized,
the shift key is placed at the end of the home row for swift
sequential operation of the space and shift keys. The umlaut is set
on the top letter row over the ie (instead of the shift as in other
languages) because the umlaut does not appear with the e. The n is
chosen as sthe home thumb-key, since it occurs much more often than
other consonants; the s and t lie side by side on the home row for
quick entry of st. Although more consonant digraphs and trigraphs
appear in German than in English, or the Romance languages, the
combinations ch, sch, and sch account for a substantial proportion
of these one-hand strokes. Their input is expedited by alloting the
t to the third finger and the h to the fourth finger on the home
row, and the c to the third finger on the top letter row. This
choice permits ch, sch, and cht to be readily stroked, even if they
are bounded by other consonants.
Keyboard Training
The keyboards of this invention minimize finger motions and
maximize alternate hand strokes, leading to faster learning and
greater performance by operators of average ability. On these
keyboards, the hands hover over home keys as fingers make simple,
independent movements from the home position. The resulting
stroking patterns differ sharply from the complex motions required
on the universal keyboard. As a result, individuals who already
know the standard keyboard will experience a minimum motor
intererece in switching to the new keyboard--and previously
established habit patterns will not impede learning the new key
configuration.
Instruction capitalizes on a central feature of the invention: the
independence of stroking motions that permits simple movements to
be practiced separately and then combined to input alphabetic
texts. Lessons can start with easy motions that occur often, and
proceed to more difficult movements appearing less frequently.
Exercises can concentrate initially on alternate-hand strokes on
home keys, beginning with keys at the edges of the hand (the thumb,
the fourth, and little fingers), that are easiest to disinguish
kinesthetically--and progress to keys in the middle of the hand
(the second and third fingers).
Limiting motor alternatives accelerates learning and lightens the
processing load on the brain, leading to swift acquisition of chain
stroking. Experimental measurements of reaction times reveal that
keyboard responses to visual stimuli are proportional to the
logarithm of the number of available response channels. Therefore
practicing a small number of alternatives hastens the formation of
appropriate motor reflexes. This training strategy succeeds on the
ten-finger keyboard because representative texts may be processed
by simple, independent finger motions. (It falls on the standard
keyboard where complex finger movements cannot be broken down into
simpler elements.)
Since input is reduced to a set of simple finger motions, basic
factors governing learning rates and ultimate performance may be
isolated and measured. Empirical studies reveal marked differences
in the dextral abilities of violinists and pianists. Similar
differences exist for keyboard operators. These differences may be
used to select trainees from a large pool of employees who will
attain high entry rates in a short time. Diagnostic tests may be
administered prior to training to identify gifted operators by
measuring the speed with which they complete repetitive strokes on
home keys and establish digital associations. Choosing individuals
with natural ability will yield better results than a random
selection, and help offset the cost of training employees on new
equipment.
Exercises can cover the keyboard in accordance with the frequency
of individual letters and chords. Lessons may start with common
characters on home keys, continue with medium frequency letters on
adjacent keys, then treat chords, and finally rare characters at
the extremities of the keyboard. Since a majority of strokes in
typical texts will lie on home keys hidden from view, instruction
will result automatically in touch typing.
Basing lessons on kinethetic principles and linguistic statistics
insures that practice exercises will match letter sequences
occurring naturally in the language. Exercises may be arranged in
groups of related and contrasting strokes to expedite conversion of
visual stimuli into digital responses. Such groups include
alternate vs. same hand motions; home key vs. other key strokes;
single strokes vs. two-key chords; strokes at the edges of the hand
(thumb, fourth, and little finger) vs. strokes at the center of the
hand (second and third fingers); and chords executed by the thumb
and another finger vs. chords executed without the thumb.
Practicing on related sets of fingers motions aids in establishing
motor associations and strengthens the weak cerebral-dextral link.
The effectivensss of particular exercises may be determined by
measuring the speed that specific digraphs are executed as a
function of practice. These measurements supply a microscopic
profile of keyboard facility and pinpoint any difficulties that may
impede learning. Such measurements can also determine the
contribution of specific stroking exercises to total processing
rates.
Instruction on the ten-finger keyboards of this invention can focus
on a limited set of motions which may be mastered before adding
other strokes. Practicing a small group of motions leads to a rapid
increase in input rates. This rate of increase diminishes with
additional practice, as stroking rates approach their asymptotic
values with extended practice. This negatively accelerated curve,
which is characteristic of motor learning, may be used to establish
optimum conditions for advancing from one exercise to another. Such
conditions can take account of individual differences in learning
and stroking ability to provide a personalized instruction program
that leads to maximum input in a minimum time.
The optimum keyboards of this invention are based on common
linguistic and kinesthetic principles. As a result, training
procedures developed for English can be applied to the foreign
keyboards presented herein because they possess similar stroking
patterns.
On the optimum keyboards of this invention, seven out of ten
strokes occur on alternate hands, and three out of four on home
keys. These repetitive patterns lead to faster responses, since it
has been experimentally established that digital response times to
visual stimuli are shorter for an ordered series of stimuli than
for a random sequence. The regular patterns occurring in natural
texts may be accentuated in instruction by employing artificial
words composed of alternating vowels and consonants. These
artificial words, which involves strokes on alternate hands, can
exclude digraphs that rarely appear in representative prose to
insure that practice exercises will be restricted to combinations
that occur often in the language.
Artifical words may be arranged in rectangular arrays in which
words undergo a minimum change from one word to the next in the
horizontal direction, but change ina quasi-random fashion in the
vertical direction. Practicing on such an array in the horizontal
direction minimizes mental strain and strengthens motor reflexes,
since most of the strokes are identical for successive words.
Mastery of these sequences may be evaluated by comparing the time
taken to input the ordered series of words in the horizontal
direction with the time needed to stroke the quasi-random series in
the vertical direction.
Such a rectangular array may be illustrated by the following group
of twelve artifical three-letter words comprising characters
stroked by the thumb, fourth, and little fingers of both hands:
nan ran rin rir hir hin han han rar nar nir nin
This array undergoes a minimum change from one word to the next in
the horizontal direction, and a quasi-random change in the vertical
direction. It excludes digraphs composed of a vowel followed by an
h because such digraphs rarely occur in English, revealing how
suitable artificial words may be constructed with the aid of
linguistic statistics. For actual practice, five-letter words are
more effective because they approximate the mean length of words in
English and offer a greater variety of stroking sequences.
A similar technique may be followed in learning the number row.
Digits may be arranged in same and alternate-hand sequences, so
numerical input will be mastered as a two-step process. The first
step identifies a digit with a specific hand; the second with a
specific finger. This two step process is feasible because the
number row has been split into even and odd digits. Entering digits
in pairs or triplets, rather than individually improves input
accuracy because numbers are mentally encoded by operators in pairs
or triplets, rather than as single digits. This procedure enables
instruction on the number row to mirror training methods used for
the alphabetic keys of this invention.
Table 1 ______________________________________ Percentage of
Occurrence of Space and Five Commonest Vowels in Six Languages
Portu- English German French Italian Spanish guese
______________________________________ 1. -- 17.6 -- 16.0 -- 17.2
-- 16.6 -- 16.7 -- 17.2 2. e 10.3 e 13.4 e 11.5 e 9.8 e 11.7 a 11.2
3. o 6.3 i 6.8 a 7.8 a 9.7 a 9.8 e 9.6 4. a 6.6 a 4.8 i 7.0 i 9.4 o
7.4 o 9.5 5. i 6.0 u 4.0 u 5.1 o 7.6 i 5.2 i 5.3 6. u 2.2 o 2.1 o
4.2 u 2.5 u 3.5 u 3.3 ______________________________________
Table 2 ______________________________________ Percentage of
Occurrence of Five Commonest Consonants in Six Languages Portu-
English German French Italian Spanish guese
______________________________________ 1. t 7.6 n 8.8 s 6.5 n 5.8 s
5.7 s 6.3 2. n 5.8 r 7.0 t 6.0 l 5.4 n 5.7 r 6.0 3. s 5.4 s 4.7 n
5.9 r 5.4 r 5.6 n 4.6 4. r 5.1 t 5.3 r 6.5 t 5.6 d 5.6 d 5.0 5. h
4.5 h 4.0 l 4.8 s 4.2 l 4.0 t 3.8 6. l 3.4 d 3.5 d 2.8 c 3.8 t 3.8
m 3.6 ______________________________________
Table 3 ______________________________________ Cumulative
Frequencies of Commonest Characters in Six Languages Portu- English
German French Italian Spanish quese
______________________________________ I 46.8 45.0 48.6 53.1 50.8
52.8 II 28.4 30.0 28.6 25.5 25.7 24.8 III 75.2 75.0 77.2 78.6 76.5
77.6 ______________________________________ I. Space and Four
Vowels II. Five Consonants? III. Space, Four Vowels, and Five
Consonants
Table 4
__________________________________________________________________________
Maximum and Minimum Letter Percentages in Nine Languages
__________________________________________________________________________
a: 13.4 (Portug.) - 5.1 (German) b: 1.9 (German) - 0.5 (Portug.) c:
4.4. (Italian) - 0.1 (Danish) d: 6.4 (Danish) - 3.4 (French) e:
19.3 (Dutch) - 10.2 (Swedish) f: 2.4 (English) - 0.8 (Spanish) g:
4.2 (Danish) - 0.7 (Spanish) h: 5.6 (English) - 0.7 (Spanish) i:
11.3 (Italian) - 5.7 (Swedish) j: 0.7 (Swedish) - xxx (Italian) k:
4.1 (Danish) - xxx (French) l: 7.5 (Italian) - 3.5 (Swedish) m: 4.4
(Portug.) - 2.4 (Dutch) n: 11.6 (Dutch) - 5.5 (Portug.) o: 11.5
(Portug.) - 2.1 (German) p: 3.0 (French) - 0.6 (German) q: 1.5
(Portug.) - xxx (Swedish) r: 8.6 (Swedish) - 5.4 (Dutch) s: 7.9
(French) - 3.1 (Dutch) t: 9.4 (English) - 4.2 (Spanish) u: 6.7
(French) - 1.5 (Dutch) v: 3.0 (Swedish) - 0.8 (German) w: 1.9
(English) - xxx (Spanish) x: 0.2 (English) - xxx (German) y: 1.8
(English) - xxx (Italian) z: 1.7 (German) - xxx (Swedish)
__________________________________________________________________________
(xxx represents a value of less than 0.1)
Table 5
__________________________________________________________________________
English Digraph Frequencies per 100,000 Letters and Spaces
__________________________________________________________________________
Second First -- a b c d e f g h -- 0 2010 805 843 528 426 714 300
949 a 498 1 140 286 284 6 46 132 8 b 19 109 10 0 1 389 0 0 0 c 92
331 0 41 0 396 0 0 378 d 1835 104 2 1 32 478 1 20 3 e 3524 472 15
275 813 271 96 72 16 f 750 111 0 0 0 150 92 0 0 g 546 100 1 0 1 240
1 20 176 h 472 653 4 2 1 2139 1 0 1 i 106 151 55 419 220 230 126
175 1 j 2 17 0 0 0 29 0 0 1 k 163 13 1 0 0 181 2 1 3 l 556 322 5 6
202 555 41 4 1 m 297 362 61 3 0 519 3 1 0 n 1530 196 3 244 851 481
34 664 7 o 737 50 62 97 121 29 686 52 16 p 108 197 0 0 0 302 1 0 53
q 0 0 0 0 0 0 0 0 0 r 1030 408 17 67 124 1168 20 60 12 s 2248 153 6
93 5 558 9 1 235 t 1641 331 2 27 1 749 5 1 2337 u 66 77 57 108 59
85 12 94 1 v 6 75 0 0 0 534 0 0 0 w 160 327 1 0 3 247 1 0 258 x 22
15 0 16 0 11 0 0 2 y 1027 12 6 6 3 77 1 1 1 z 5 14 0 0 0 35 0 1 0
Totals 17,607 6,627 1,264 2,561 3,269 10,294 1,922 1,607 4,479
Second First i j k l m n o p q -- 1187 95 88 414 693 378 1248 687
34 a 230 6 75 649 185 1270 3 117 1 b 66 11 0 155 2 0 142 0 0 c 155
0 110 97 1 1 488 0 2 d 291 4 0 28 11 19 138 1 1 e 109 3 16 349 232
907 42 107 29 f 181 0 0 42 0 0 322 0 0 g 96 0 0 40 4 39 99 0 0 h
563 0 0 9 8 18 342 1 0 i 1 1 39 299 218 1554 447 57 8 j 2 0 0 0 0 0
38 0 0 k 71 0 1 10 1 40 7 1 0 l 402 0 19 417 20 4 254 14 0 m 207 0
0 3 59 6 225 136 0 n 221 7 40 47 15 62 295 4 3 o 57 4 52 232 356
1071 178 141 1 p 88 0 1 166 11 0 214 91 0 q 0 0 0 0 0 0 0 0 0 r 436
0 62 65 102 107 471 27 1 s 345 0 33 45 45 15 251 120 7 t 753 0 0 75
20 6 713 2 0 u 67 0 1 226 81 271 7 94 0 v 157 0 0 0 0 0 41 0 0 w
261 0 1 9 1 62 163 1 0 x 18 0 0 0 0 0 2 42 0 y 22 0 1 9 15 8 109 13
0 z 9 0 0 2 0 0 4 0 0 Totals 6,001 137 544 3,405 2,095 5,845 6,255
1,666 89 Second First r s t u v w x y z -- 456 1210 2783 203 113
1068 1 149 4 a 692 608 927 73 137 44 14 170 11 b 74 24 9 142 4 0 0
100 0 c 93 12 247 82 0 0 0 21 0 d 65 79 1 79 11 5 0 40 0 e 1323 788
280 15 170 86 122 111 3 f 138 2 55 63 0 0 0 5 0 g 131 34 12 49 0 0
0 10 0 h 58 8 103 53 0 3 0 30 0 i 297 720 722 7 164 0 13 0 41 j 1 0
0 43 0 0 0 0 0 k 2 30 1 2 0 2 0 7 0 l 8 82 69 83 20 9 0 301 0 m 25
60 1 82 0 0 0 39 0 n 6 294 618 49 28 4 2 73 2 o 805 184 277 634 124
233 9 26 3 p 268 35 54 64 0 1 0 6 0 q 0 0 0 87 0 0 0 0 0 r 72 270
225 82 39 8 0 151 1 s 2 250 720 184 1 21 0 31 0 t 225 205 128 149 0
50 0 132 3 u 325 292 288 1 2 0 3 4 2 v 0 1 0 1 0 0 0 4 0 w 22 20 4
1 0 0 0 2 0 x 0 0 27 2 0 0 0 2 0 y 7 58 14 1 0 4 0 0 1 z 0 0 0 1 0
0 0 2 6 Totals 5,051 5,394 7,621 2,237 821 1,548 164 1,420 79
__________________________________________________________________________
Table 6 ______________________________________ Percentage of
One-Hand Digraphs on Ten-Finger Keyboard Left Hand Right Hand Both
Hands ______________________________________ Chords 11.01 7.40
18.41 Two Home Keys 2.67 1.27 3.94 Home & Other Key 1.83 3.94
5.77 Two Other Keys .05 1.31 1.36 Total 15.56 13.92 29.48
______________________________________
Table 7 ______________________________________ One-Hand Trigraphs
on Standard Keyboard per 100,000 Letters and Spaces* Frequency No.
of Trigraphs % in Group Cumulative %
______________________________________ 320- 4 1.87 1.87 160-320 10
1.96 3.84 80-160 28 3.10 6.93 40-80 57 3.16 10.09 20-40 103 3.08
13.16 10-20 126 1.82 14.99 ______________________________________
*Omits the trigraph letter-space-letter
Table 8 ______________________________________ One-Hand Trigraphs
on the Ten-Finger Keyboard per 100,000 Letters and Spaces*
Frequency No. of Trigraphs % in Group Cumulative %
______________________________________ 80- 4 .87 .87 40-80 8 .44
1.21 20-40 12 .36 1.57 10-20 14 .21 1.78
______________________________________ *Omits the trigraph
letter-space-letter
* * * * *