SOFT DISPLAY KEY FOR KANJI INPUT 
Jouko J. Sepp~nen 
HELSINKI UNIVERSITY OF TECHNOLOGY 
Computing Centre 
02150 ESPOO 15, FINLAND 
Abstract. The concept of a soft 
display key as applied to input of 
large character sets or vocabularies 
such as Kanji, the ancient Chinese 
ideographic script is discussed. The 
Japanese orthography and the necessity 
of using Kanji characters in data 
terminals are explained. Problems 
arising from the number and complexity 
of Kanji symbols for the manufacture 
and use of keyboard devices are stated. 
A review is made of devices and methods 
presently used or suggested. The 
feasibility of the soft display key is 
then demonstrated. Some requirements 
for the design and implementation of a 
soft display keyboard for Kanji are 
considered. In conclusion, 
implications to man/computer interface 
design, human factors engineering and 
hardware unification and 
standardization are stated. 
Keywords. Display key, soft 
panel, touch display, character set, 
Kanji input, programmed interface, data 
terminal, man/computer dialogue, human 
factors, cultural variation. 
Introduction 
The Kanji Script. The Ancient 
Chinese ideographic writing system, 
Kanji, is today used in China, Japan 
and to some extent in Korea. A 
principal advantage of an ideographic 
script is that its understanding does 
not suppose knowledge of the spoken 
language. Written Chinese, e.g., is 
understood all over the country, though 
the spoken languages are mutually 
incomprehensible /~/. The main 
disadvantages are obviously the large 
number and graphical complexity of 
written characters and the consequent 
hardship of learning and writing them. 
Once learned, reading, instead, does 
not present equal difficulty thanks to 
the excellent pattern recognition 
ability of man. Complex meanings are 
conveyed in condenced graphical 
patterns, which are grasped at a 
glance. 
Kanji Data Terminals. The real 
prohibitions are, however, encountered 
in the design and manufacturing of 
typing machines and data terminals as 
well as in their operation. The 
man/computer interface is a serious 
bottleneck already with the European, 
modestly sized alphabet and keyboard. 
Particularly burning this problem is 
being felt in Japan, where the computer 
and information industries are now in 
full swing. 
In the early beginning data 
processing in Japan was done on the 
basis of romaji, the European alphabet. 
In Japanese business and culture the 
Chinese Kanji and the Japanese Kana 
writing systems, however, play the main 
role. Therefore, in Japan there is no 
true solution to computerization 
without the use of Kanji /I/. 
The demand for data terminals is 
increasing rapidly. For overcoming the 
technical, manufacturing and human 
factors problems involved in Kanji 
input a number of different approaches 
have been made or suggested. Several 
kinds of devices and systems based on 
very different principles are in use, 
while many have remained designs only. 
Some of these are reviewed below in 
order to get insight into the problem 
and the present situation. 
A technique based on the display 
input principle is then introduced and 
suggested for coping with the Kanji 
input problem. The technique is 
demonstrated capable of' entering all 
Kanji characters on a normal western 
size keyboard with normal size 
characters and operable by finger. 
--287-.- 
The Japanese Orthography 
The Japanese orthography is rather 
complicated. Two kinds of script are 
used - the Kanji and the Kana. Kanji 
is the ancient pictographic writing 
system adopted from China about 1700 
years ago. The Kanji characters used 
today are either original Chinese 
symbols or symbols later formed or 
modified in Japan. 
The Kana Syllabaries. Kana is the 
Japanese phonemic writing system. It 
consists of two syllabic alphabets - 
Hiragana and Katakana. These are 
parallel character sets, consisting of 
46 syllabic characters and two 
diacritics. Both Hiragana and Katakana 
denote the same set of syllables, but 
are used for different purposes. Their 
graphics have been derived from Kanji, 
but are considerably simpler. 
Particularly Hiragana has been strongly 
simplified into a kind of shorthand. 
All three character sets are 
necessary by tradition. For Japanese 
words both Chinese characters and 
Hiragana are used. Hiragana is also 
used to form grammatical endings and 
other syntactic units to Kanji words, 
while loan words from foreign languages 
are usually transcribed in Katakana. 
In addition, Katakana is often used in 
polite addressing forms. The patterns 
of usage are not, however, well 
defined. Ever more often today one can 
see words of Chinese origin written in 
either Kanji or Kana or both 
intermixed. 
Kanji Character Sets. 
Dictionaries of ' varying coverage In 
present day use record 49,964, 14,942, 
9,921 and 3,885 Kanji characters 
respectively /2/. The number of 
characters sufficient for everyday use 
such as reading newspapers and 
magazines varies from 2000 to 3000. 
About 2000 characters have been 
designated as essential and selected as 
a standard set for publishing. A set 
of 881 characters is used in basic 
education and further a minimum of 1968 
characters have been selected for 
educational purposes by the Japanese 
Ministry of Education /2/. 
Despite the fairly large numbers 
of characters recorded in dictionaries, 
some 200 most frequently used Kanji 
account for over 50 per cent of the 
usage in text while 800 Kanji 
supplemented with 50 Hiragana already 
account for 90 per cent of ordinary 
text /3/. 
The Inadequacy of Kana. For 
practical purposes such as typing, it 
would be desirable to be able to use 
the Kana syllabaries, since they can be 
managed with conventional keyboard 
techniques. But unfortunately the Kana 
systems are linguistically inadequate. 
The problem is polysemy. It is not 
uncommon that several Kanji characters 
with different meaning have equal or so 
similar pronunciation that they become 
identical in Kana. There are e.g. 
some 70 Kanji characters, which are 
pronounced and transcribed as "Shou" in 
Kana /4/. On the other hand many 
characters have become to denote 
concepts quite different from the 
original, which happened to have 
similar pronunciation /5/. Thus the 
phonetic and semantic inadequacies of 
the phonemic scripts necessitate the 
use of the old Kanji, which is 
unambiguous. 
Problems with Kanji Input 
The main problems of using Kanji 
are connected with the input devices. 
For output, a Kanji printer or display 
though more expensive than its European 
counterpart, can be realized by 
standard output technologies such as 
matrix printer and CRT display, see 
e.g. /2,4 and 6/. The character print 
head or display matrix only must have 
higher order to give the required 
graphical resolution. Kanji printers 
are available, which use print head 
dimensions of e.g. 15 by 18 or 22 by 
24 dots. 
But for input of Kanji characters 
we need a keyboard, which has a great 
many keys or some special arrangement 
by which all necessary characters can 
be entered. I~ fact, an equipment, 
which would allow to encode all Kanji 
characters would be simply absurd to 
implement and to operate by 
conventional keyboard techniques. In 
developing keyboards for typewriter, 
telex and data terminals it has been 
necessary to severely restrict and 
carefully select the set of characters 
to be included. Yet it has been 
necessary either to squeeze many 
characters per key or to reduce the key 
size so much that it can be operated 
only by a special implement. Despite 
this, sophisticated special techniques 
for input of nonstandard characters are 
necessary in many applications. 
Nonstandard characters do frequent in 
various texts and subject areas. The 
difficulty with them is not only that 
they are sometimes indispensable, but 
also that different sets of nonstandard 
-288- 
characters are needed 
application to another. 
from one 
S.tandard Data Processin~ Set. For 
the purposes of data processing the 
Information Processing Society of Japan 
has instituted a set of 6100 characters 
as a standard set /2/. These include 
the 1968 most common Kanji characters 
plus Hiragana and Katakana, a set of 
system oriented Kanji, a set of other 
system oriented symbols and the 
ordinary European alphanumerics /2/. 
Not all of these are, however, usually 
available on present devices. E.g. 
for the terminal described in /2/ the 
following sets have been selected: 
Most often used Kanji 1,968 
Kanji for general use 1,850) 
Kanji for" personal name 92) 
Kanji for auxiliary use 26) 
Additional Kanji 2,538 
System oriented Kanji 64 
System oriented symbol 95 
Alphanumeric & symbol 94 
Katakana & symbol 92 
Hiragana & symbol 85 
Total 4,936 
In the Japanese card punch key 
entry device developed by IBM Japan and 
described in /3/ there are 2,304 
characters. In order to make the 
keyboard manageable by the human 
operator, the size of keys must have 
been made very small. In the IBM 
equipment the key dimension is 4 mm. 
This has permitted to fit the keyboard 
on the table of a normal size card 
punch device. 
Using such a keyboard does, 
however, cause considerable eye strain 
to the operator and requires a lot of 
hand transport. Moreover, special 
means of key actuation such as a stylus 
as in /3/ or a pantograph mechanism as 
in /2/ and /7/ must have been 
introduced. 
Decgmposition Schemes.. Attempts 
have been made to develop rational 
decomposition schemes in order to break 
the characters down into simpler common 
elements. This would allow reduction 
of the keyboard size. The characters 
could then be piecewise reassembled by 
typing from their constituent 
components, see e.g. /8/. From 
technical viewpoint this approach would 
seem very advantageous. But, 
unfortunately there is little natural 
systematics and consistence in the 
graphical structure of the characters. 
Therefore any such scheme becomes 
artificial and difficult to use. In 
addition, such schemes are often 
insufficient of description and can 
sometimes specify only classes of 
characters. 
Character Arrangement. Still 
another source of problems is the 
arrangement of characters on the 
keyboard. In Kanji there is little 
inherent systematics, which could be 
complied to. To minimize search time 
and hand or stylus transport, high 
frequency characters are often assigned 
to a central area. E.g. the keyboards 
described in /7/ and /15/ have used 
this principle. 
One of the imperative factors in 
key arrangement is, however, the 
historical precedent /16/. In Japan 
this is determined by the Kanji 
Teletype, also referred to as Kantele, 
which has been used for thirty years in 
the newspaper industry /3/. Data input 
equipment usually conform to the 
phonetic order, which is generally used 
for typing machines. E.g. the 
equipment described in /7/ applies this 
arrangement. 
Typing Speeds. Despite of the 
apparent difficulties, excellent typing 
performance can be achieved in Kanji 
input through practicing. The figures 
of words per minute and accuracy 
reported in /3/ correspond to those 
that can be observed on skilled western 
card punch operators. Thus, the 
enormous difference between character 
set size and the keying techniques in 
the two cultures causes little 
difference in the level of skilled 
performance /3/. The small size of 
characters causes, however, more eye 
strain to the operator and the large 
size of the keyboard more fatique to 
hand muscles on the Japanese equipment. 
A Review of Techniques 
An account of some techniques and 
existing devices for Kanji input is 
given in /4/. These and some others 
found in litterature are briefly 
reviewed here. 
The Kanji Teletype. According to 
/4/ the Kanji Teletype (Kantele) is the 
most commonly used encoding equipment. 
Kantele has 192 keys, each of which 
bears labels of 13 Kanji characters. A 
shift key pad of 13 shift keys is used 
to select among the 13 characters on 
289 
each input key. The number of keys has 
thus been reduced significantly, but 
there are still considerable drawbacks: 
* The amount of hand transport and 
searching is still considerable 
* The lack of logical arrangement 
plagues character localization 
* There is no facility for either 
verification nor for nonstandard 
character input. 
Operator performance observed with 
the shift key method seems to be 
inferior to methods using stylus. 
A Chinese Typewriter System. In a 
Chinese Typewriter System abstracted in 
/9/, a keyboard is provided for quick 
access to a master file of digitized 
Kanji characters. On top of the 
keyboard is a character reference 
sheet, which is organized according to 
the order of the Chinese phonetic 
alphabet. By appropriate keying of a 
desired character, a mechanism within 
the control unit will access the master 
file. A graphic display is provided 
for verification of the entered 
characrter. Up to 9600 characters are 
available in the system. 
The Sinotype Syste.m. This 
equipment is based on the principle of 
composing characters from a small set 
of strokes. There are 21 different 
elementary strokes from which each 
character can be constructed as a 
unique combination. An average of six 
strokes are required to form one 
character. The disadvantages are: 
The difficulty of decomposing 
characters into a set of strokes 
* The difficulty of remembering 
the stroke combinations, which 
are different from the tradit- 
ional calligraphy. A special 
combination dictionary must be 
used. 
The Sinowriter System. In this 
system developed by IBM a Kanji 
character is formed from two parts, the 
upper and lower half. Both of these 
are classified using 36 standard 
subpatterns. These operations are, 
however, not sufficient to specify a 
character uniquely. A set of at most 
16 characters are displayed on a CRT, 
from which the operator can then select 
the correct one. According to /4/ this 
system has been designed for 
foreigners, who do 
Kanjil 
not understand 
A.Kanji Data Terminal. In /2/ an 
input arrangement is described, which 
uses a printed character sheet and a 
superimposed binary code film sheet. A 
character is entered by moving a 
pantograph lever mechanism carrying a 
code reader device onto the selected 
character. On pushing a button the 
character code is flashed on a LED 
display and read from the film by an 
array of photo transistors. 
This system allows to use two 
kinds of Kanji character boards with 
different character arrangements. The 
numbers of characters in the two sets 
are 2,205 (Onkun-jun) and 2,940 
(Bushu-Kakusu-jun) respectively. 
The Rand Tablet. This is a 
general purpose graphic input device 
developed by the Rand Corp. The system 
for Kanji input allows hand written 
stroke sequences to be drawn on the 
Tablet, matched with a pattern 
dictionary and displayed on a CRT. The 
disadvantages are: 
* The slow speed, the amount of 
manual effort and difficulty of 
correctly drawing a character 
* The complexity and inadequacy 
of pattern matching procedures. 
Machine recognition of Kanji is 
not a solution to on-line Kanji input, 
because the human effort required to 
handwrite a character is considerably 
greater than the effort required to 
read it on the keyboard and to type it. 
If this, as it is, the case with the 
Roman letters and the Arabic numbers, 
then let alone with Kanji, whose 
calligraphy is work of art. 
A Pattern Structural Coding 
Method. In /8/ a method is described, 
which enables generative description 
and definition of Kanji like patterns. 
The method allows systematic encoding 
of an unlimited set of patterns in 
terms of a small number of 
alphanumerically coded strokes and 
concatenation operators. Disadvantages 
of this method are: 
* The need of long alphanumeric 
code strings for characters 
* Insufficiency of the coding 
system to express unique stroke 
variations. 
-290- 
Automatic Phonetic to Kan~i 
Conversion. several systems have been 
developed for automatic conversion of 
phonemic Kana script into Kanji. These 
systems must rely on methods of 
grammatical analysis of the phonemic 
script. Reference files are necessary 
for the solution of ambiquities. The 
disadvantages are: 
* The need of complicated natural 
language syntax analysis algorithms 
and large reference files 
* The inadequacy of the algoritms 
as to correctness of translation. 
Bunkai-Hatsuon Conversion Method. 
The subject of /4/ is also a conversion 
method from phonemic script to Kanji. 
It makes use of the fact that many 
Kanji characters have several 
pronunciations. These can be used to 
reduce the ambiquity in mapping 
phonemic script to KanJi. The method 
is called Bunkai-Hatsuon. 
Tests and comparisons reported in 
/4/ indicate that on the average four 
key strokes are adequate to uniquely 
identify a Kanji character as opposed 
to six strokes w~th the Sinotype. 
Input rates of 40 to 50 characters per 
minute have been achieved. According 
to the authors this is not fast enough 
for all purposes, but it satisfies the 
requirements for some man/computer 
communication needs and comes close to 
an "easy to use" system. An advantage 
of this system is that it can be used 
for any size of character sets. The 
only modification required is t~ add 
the new Kanji characters to the system 
dictionary. The system requires an 
advanced computer system for its 
support (Tosbac 3400). 
Kanji Input System. A Kanji 
keyboard has been developed in /7/, 
which enables incorporation of 
nonstandard characters as well. The 
keyboard has in addition to the 
standard keyboard three special 
sections. These are called Spare Area, 
Function Input and Pattern Input 
sections. 
On the Spare Area different sets 
of characters can be provided by using 
replaceable character sheets and 
function keys for sheet identification. 
Customized character sets can be 
defined for varying applications. 
The Pattern Input section enables 
introduction of new characters to the 
system. Character patterns can be 
interactively constructed from strokes 
using stylus and a 64 by 64 point grid. 
The generated patterns are added to the 
repertoire of nonstandard patterns and 
assigned with a sheet number and key 
position. The defined character 
pattern is then hand printed on the 
specified position of the sheet to 
enable selection. When entered, any 
character can be displayed for 
verification by the operator. 
In principle the system can handle 
an unlimited number of Kanji 
characters, but its operation is 
obviously quite impractical. In 
addition it also requires a 
considerable computer system (NEAC 
2200/200) for its support. 
The method described above is in 
principle similar to that used in some 
programmable terminals and pocket 
calculators, in which the user can 
define various functions, assign them 
to special function keys and label them 
by handprinting on overlay sheets 
accordingly. This comes close to the 
idea of a programmable display key, in 
which not only the function, but also 
its label is stored in the memory and 
displayed to the user for reference at 
program control. 
The Soft Display Key Principle 
We now confine ourselves to 
suggesting a method for Kanji input, 
which is based on the programmable 
display key concept. The display key, 
also referred to as videoclavis in /11/ 
- can be thought of as a normal input 
key, but with the difference that its 
key top caption, instead of being 
engraved, painted or otherwise made and 
fixed permanently on the key, is now 
generated by a display component under 
program control. The character images 
are stored in memory, either read only 
or renewable, and presented to the user 
for reference as appropriate. At any 
system state only a relevant set of 
symbols or words are displayed as a 
menu. At the touch of a display key, 
the whole setup, some part of it or 
nothing at all may change according to 
how that step had been programmed. 
Though simple in principle this is 
a brave idea promising to upset present 
conceptions about keyboard and panel 
arrangements as well as the principles 
of man/computer interface design. 
Conceptually the soft display key 
--291--- 
is related to the touch sensitive 
screen /10/. The latter makes the 
display screen also an input device, 
while the former makes the keyboard 
also an output device. Both allow to 
improve the man/computer interaction by 
offering a fully virtual human 
interface. 
As applied to Kanji input, the 
main advantage of the virtual interface 
is that the keyboard equipment becomes 
independent of the size of the 
character set. Consequently the size 
of the keyboard can be reduced to what 
is considered most suitable from 
operating and manufacturing points of 
view. 
In addition, the very same 
keyboard can be equally well used for 
Hiragana, Katakana, Latin, Cyrillic or 
whatever character set is needed. Very 
large character sets such as Kanji, 
must be structured in some way so as to 
allow quick access to the aimed 
character. This can be done by 
breaking the set down into subsets by 
an appropriate scheme. Features such 
as subarea on a traditional keyboard, 
phonetic order, stroke number, radical 
component, writing sequence, 
grammatical or semantic category or 
perhaps still other characteristics, 
which a European, only superficially 
familiar with Kanji, cannot imagine of. 
A tree like access structure with 
equally sized and appropriately named 
subdirectories would guarantee most 
efficient access path. Actual 
characteristics of Kanji and learned 
conventions may suggest differences to 
obtain a most practical access scheme. 
The input display principle is a 
very general idea and its essential 
functions can be realized by using 
alternative technologies available for 
display and sen~ing. Similarly both 
hardware and software support systems 
allow great freedom of design decision. 
Display technologies are becoming 
available, which allow fabrication of 
composite matrix element display 
structures sufficient for the 
resolution required by Kanji. The 
display component may be based on light 
emitting diode (LED), liquid chrystal 
display (LCD), electr~luminence (EL) or 
other flat panel display technology. 
Various technologies are also 
available for implementation of the 
switching field necessary for sensing 
the presence of a finger on some 
display area. The switching function 
can be based on contactive, capacitive 
or resistive effect, photo detection, 
acustic signal etc. switching 
components. 
The switching system can either be 
integrated into the display system or 
overlaid to it. On the panel side the 
two systems are, however, independent 
of each other. They are oniy 
coordinated with each other with 
respect to location. On the system 
side they are associated with each 
other under common program control. 
The discussion of both technical 
design objectives as well as specific 
applications would, however, involve 
expert knowhow of both display 
electronics as well as Kanji script, 
the Japanese language, type of 
application, user environment etc that 
we do not possess. Their discusssion 
must therefore lie outside of the scope 
of this paper. The aim of this talk 
has only been to demonstrate the 
feasibility of the idea and to point 
out some of its implications. 
Some Implications 
A number of key problems involved 
in Kanji input devices and their use 
seem to find their solution in the soft 
display key input principle. The major 
problems solved and advantages achieved 
are as follows: 
* The number of keys and the size 
of the keyboard can be reduced 
to what is considered normal 
* ~et normal key and character size 
can be maintained for good legib- 
ility and convenient operation 
* An unlimited number of Kanji 
characters can be accommodated 
* New characters can be added by 
definition as necessary 
* The character set can be adapted 
or changed from one application 
to another 
The character layout can be 
changed from one convention to 
another according to user skill 
* The same keyboard can be used 
for Kana, ASCII and still other 
character sets when necessary 
at the same time 
- 292-- 
* The keyboard can also be used 
for user interaction such as 
prompting, indication, etc 
Moving mechanical parts can be 
fully eliminated and all keys 
can be made identical to allow 
cost efficient mass production. 
Optimal Key and Keyboard Size. 
The keyboard can be designed into 
optimal size from manufacturing and 
human factors points of view. Yet the 
key and character size can be made 
large enough for good legibility and 
convenient actuation by bare finger. 
The need for special arrangements 
for nonstandard characters and 
verification of entered characters 
becomes unnecessary. 
Virtual Character Sets. Through 
menu structuring and paging an 
unlimited number of characters can be 
supported independently of the number 
of physical display key fields. It 
becomes possible to use different size 
keyboards for a given character set and 
different character sets for a given 
size keyboard. The only limiting 
factors are memory space and display 
raster resolution. New characters can 
be added to the system by programmed 
definition or by loading from external 
media. 
Portability 'and Adaptability. 
Software portability and adaptability 
are qualities, which reflect the ease 
of moving programs from one hardware 
environment to another and modifying 
them to fit different objectives /15/. 
The programmed key labelling principle 
allows these qualities to be extended 
to the man/computer interface. 
Character set device independence 
provides for a capability, which can be 
called human interface portability. 
This means that a character set layout 
and menu structure can be transferred 
from one keyboard to another simply as 
a software copy. If not directly 
compatible, the conversion can be made 
on software level. This quality does 
contribute to reduced need of operator 
retraining and higher equipment 
usability. 
Adap.tabilit~. The need for 
adaptability emerges from system 
dependence on the application and user 
environment. System adaptability 
reduces this dependence and extends the 
scope of potential system application. 
The display key concept does not 
eliminate variation or incompatibility 
among different application or user 
environments, but it allows the system 
user interface to be adapted toand 
complied with the different conventions 
and requitements by modification and 
adjustment of the software. Even minor 
operator preferences and habituations 
can be accommodated easily. In many 
application environments considerable 
savings could be achieved, if 
customization and development could be 
further done by the user along with his 
developing experience. The virtual 
interface does allow such development. 
Unified Hardware. In spite of all 
the flexibility and variation it is 
possible to develop unified display key 
component designs and to standardize 
the panel and keyboard structures for 
cost effective mass production. 
Acknowledgements 
I wish to thank Karri Kuusikko, 
Harri Hal~n, Heikki Mallat, Anu Arponen 
and Reichi Nichizawa for their help in 
the course of the preparation of this 
paper. The views presented in the 
paper are the responsibility of the 
author alone. 

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