electronics

Article One Row Keyboard: The Concept of Designing Common Layout for Physical and Virtual Keyboards

Radosław Puka * , Piotr Łebkowski and Jerzy Duda

Faculty of Management, AGH University of Science and Technology, 30-059 Cracow, Poland; [email protected] (P.Ł.); [email protected] (J.D.) * Correspondence: [email protected]

Abstract: The development of technology brings the computerization of everyday life. The most common device used to communicate with a computer is the keyboard. Many papers have been devoted to the study of computer keyboards and virtual keyboards. The authors of this study propose a new concept of a single line keyboard named One Row Keyboard (ORK) which can be applied for both computer and virtual keyboards. Applying the proposed concept enables the number of keys on the keyboards to be reduced significantly. This allows for the development of keyboards even on really small mobile devices. The article also presents a new method of assigning characters to keys for the ORK and shows the use of this method to create exemplary ORK layouts. One Row Keyboard is also the first concept that makes it possible to create a fully alternating keyboard. Noteworthy is that the criterion of maximizing alternation is the most popular criterion for keyboard optimization used in the studies devoted to computer keyboards as it leads to an increase in typing speed and  decrease in the number of errors. 

Citation: Puka, .; Łebkowski, P.; Keywords: ; one row keyboard; fully alternating keyboard; human–computer interaction Duda, . One Row Keyboard: The Concept of Designing a Common Layout for Physical and Virtual Keyboards. Electronics 2021, 10, 663. 1. Introduction https://doi.org/10.3390/ Since Christopher Sholes patented the with the original QWERTY key- electronics10060663 board in 1878 [1], a number of keyboard designs of varying form and purpose have been developed. One of the most popular keyboards alternative to the computer QWERTY Academic Editor: George arrangement is the Dvorak keyboard [2]. In their research, Dvorak and Dealey presented a A. Tsihrintzis number of factors affecting the typing speed for a keyboard. They distinguished alternating typing as one of the most important factors. Research has continued on the impact of Received: 3 February 2021 various factors affecting typing speed on a computer keyboard [3,4] and the very keyboard Accepted: 10 March 2021 Published: 12 March 2021 arrangement problem is still the subject of scientific interest [5–7]. Anson et al. [8] proposed relocation of several letters to the numeric row. Smith et al. [9] presented the postulate

Publisher’ : MDPI stays neutral that the physical shape of the keyboard should be modified. McLone et al. [10] proposed a with regard to jurisdictional claims in curved keyboard, which is more ergonomic than the “standard” keyboard. published maps and institutional affil- As technology advanced and the use of mobile devices became gradually more com- iations. mon, first keyboards dedicated to such devices were developed. The OPTI [11] and FI- TALY [12] keyboards deserve particular attention; they are equipped with four and two, respectively, keys. The Metropolis [13] and ATOMIK [14] arrangements are other interesting projects, featuring hexagonal keys. Hsiao et al. [15] proposed a modification in QWERTY layout where all keys are arranged in one line. Bi et al. [16] proposed keyboard Copyright: © 2021 by the authors. Licensee MDPI, Basel, . optimization for more than only one . The papers devoted to the keyboard ar- This article is an open access article rangement problem have more and more often concerned the issue of the development of distributed under the terms and keyboards for mobile devices [17,18] and studying the effect of, inter alia, the size of the keys conditions of the Creative Commons on the correctness of the text typed [19,20]. Chang et al. [21] studied the impact of the button Attribution (CC BY) license (https:// position on muscle activity, touch time, and discomfort. Xiong and Muraki [22] suggested creativecommons.org/licenses/by/ that tapping smaller buttons increase muscle effort. The single-row keyboard (named by the 4.0/). authors as 1Line keyboard), dedicated to mobile devices, was presented in [23]. This paper

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emphasized the importance of limiting the number of keys on virtual keyboards, necessary for their comfortable use. The article [24] proposed a virtual single-row keyboard that uses chordred methods for input . In the article [25], an interesting proposal was presented to enter one character using a combination of two buttons (physical and virtual) on a . The article [26] proposed a single-row keyboard, which can potentially be used both on a computer keyboard and on a mobile device. However, the proposed keyboard requires a dedicated device and special software to use it on a PC computer. Problems of creating keyboard layouts both on virtual and computer keyboards, as well as adapting computer keyboard layouts to the needs of mobile devices, are problems still present and analyzed in the literature [26–28]. Due to the comfort of using one layout on both types of devices resulting, among others, from the lack of necessity to switch between different layouts, this problem seems to be very important. According to the authors, it can be decisive for the popularization of newly created layouts and strongly limits the popularity of layouts dedicated to only one type of device. In the presented paper, the authors, when designing layouts (and assigning characters to keys), took into account the most important criteria for the optimization of computer keyboard layouts, including alternation of entering subsequent characters as well as the small size of keyboards in mobile devices. The proposed concept of designing One Row Keyboard (ORK) is the first concept that allows to create a fully alternating keyboard (for a computer keyboard). The significance of the hand alternation criterion was confirmed, among others, in papers [6,29,30]. In addition, due to the limited number of keys and the resulting possibility of increasing the size of the keys, ORK virtual keyboards seem to be more comfortable than keyboards imitating a full computer keyboard. Section2 describes the main assumptions of the proposed ORK keyboards and ad- ditionally proposes a method of creating the ORK keyboard design. Section3 shows examples of ORK keypad groups. Discussion of the results is presented in Section4. The last section summarizes the article.

2. One Row Keyboard With the development of personal computers and their increasing use in everyday life, the problem of communication with a computer is gaining importance. The introduction of touch interfaces meant that the classical computer keyboard was replaced by a , which is usually much smaller. Despite this, the QWERTY proposed in the 19th century is nowadays used in most mobile devices, even though they have much smaller sizes. This is related to the necessity to use many virtual keys, the small size of which may cause various difficulties in precise typing [22]. Thus, the main objective of this paper is to propose a concept of keyboard layout which can be used equally on a computer keyboard and on mobile devices, and at the same time will be adapted to the specifics of both types of devices. In the proposed solution, due to the small size of mobile devices, the authors focused on reducing the number of keys on the keyboard. Reduction in the number of keys is possible using the functionality. Dead keys allow to modify the character assigned to the key struck immediately after the dead key has been pressed. This reduction was primarily aimed at the possibility of increasing the size of the keys on virtual keyboards used in mobile devices. When considering the computer keyboard, the authors took into account one of the most popular optimization criteria used in most of the studies devoted to the topic of keyboard layout optimization, i.., typing alternation. As a limitation, the authors adopted the elimination of vertical movements of fingers while typing. This reduces fatigue in the hands caused by the movement of fingers. It could also reduce the number of typing errors resulting from striking a wrong key by a hand moving over the keyboard. Electronics 2021, 10, FOR PEER REVIEW 3 of 17

Electronics 2021, 10, 663 3 of 17 2.1. Definition of ORK Keyboard A keyboard satisfying the above assumptions is the keyboard proposed by the au- 2.1.thors—the Definition ofOne ORK Row Keyboard Keyboard (ORK). A keyboard can be classified as an ORK keyboard if itA satisfies keyboard the satisfying following the condition: above assumptions is the keyboard proposed by the authors—the One Row Keyboard (ORK). A keyboard can be classified as an ORK keyboard ifDefinition it satisfies the 1: following[All condition: keys are located in one row] and [they are operated by all fingers except thumbs or operated only by thumbs]. Definition 1: [All letter keys are located in one row] and [they are operated by all fingers exceptThis thumbs definition or operated distinguishes only by thumbs]. between two types of keyboards: • keyboards supporting typing with all fingers, • Thiskeyboards definition adapted distinguishes to typing between only two types with of thumbs keyboards: (or any other pair of fingers). • keyboards supporting typing with all fingers, • keyboardsThe above adapted differentiation to typing only is with based thumbs on (or anye size other of pair the of fingers).keyboards used. Some key- boards,The above such differentiation as those in mobile is based onphones, the size are of the generally keyboards too used. small Some to keyboards, allow comfortable han- suchdling as when those in using mobile all phones, fingers. are Figure generally 1 presen too smallts an to allowexample comfortable of an ORK handling type keyboard lay- whenout. using all fingers. Figure1 presents an example of an ORK type keyboard layout.

Letter keys

Keys operated by thumbs

FigureFigure 1. Example1. Example of One of RowOne Keyboard Row Keyboard (ORK) keyboard (ORK) layout.keyboard layout.

The example is a general one and presents the two types of ORK keyboards described. In the caseThe of example a thumb-only is a keyboard, general the one letter and keys presents would be the operated two onlytypes with of thumbs. ORK keyboards de- scribed.An enhancement In the case of of the a ORK-typethumb-only keyboard keyboard, is the ORK+ the letter type keyboardkeys would which be must operated only with satisfythumbs. the following additional condition: An enhancement of the ORK-type keyboard is the ORK+ type keyboard which must Definition 2: A keyboard has to be implementable on standard computer keyboards. satisfy the following additional condition: DefinitionThus, an 2: ORK+ A keyboard keyboard has must to simultaneously be implementable meet both: on standard condition forcomputer the ORK keyboards. keyboard and condition for the ORK+ keyboard. TheThus, ORK+ an type ORK+ has been keyboard proposed must in order simultaneously to enable the development meet both: of a keyboardcondition for the ORK whichkeyboard could and be used condition for both mobilefor the as ORK+ well as keyboard. standard PC keyboards (e.., compliant with the ISO/IEC 9995-2:2009 standard [31]). AnThe example ORK+ of type an ORK+ has typebeen keyboard proposed arrangement in order withto enable 10 letter the keys development is shown in of a keyboard Figurewhich2. Thecould assignment be used of for keys both to fingers mobile in the as presented well as arrangementstandard PC is the keyboards same as in (e.g., compliant touchwith typing the ISO/IEC on a similar 9995-2:2009 keyboard [ 4standard]. [31]). InAn order example to improve of an the ORK+ ergonomics type ofkeyboard typing, the arrangement authors propose with an 10 alternative letter keys is shown in toFigure the illustrated 2. The assignment arrangement ofof thekeys characters to fingers of the in ten-keythe presented ORK+ arrangement. arrangement The is the same as in operation of the letter keys in the arrangement presented in Figure3 is the same as in touchtouch typing. typing on a similar keyboard [4]. The ORK+ arrangements proposed below is shown on an alternative version of a keyboard arrangement (Figure3). The presented version of the keyboard layout allows to increase the maximum number of ORK+ keys to twelve. The arrangement shown in Figure2 limits the maximum number of keys for the ORK+ layout to eleven. In this paper, the authors will focus only on the keys forming the ORK+; therefore, only those keys will be shown in illustrations presenting subsequent arrangements. In the case of the arrangements with 11 letter keys, the keyboard will be extended by one key, located directly to the right side of the key operated by the right-hand little finger. In order to be able to create an ORK+

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keyboard with 12 keys, it is necessary to shift (in relation to the one shown in Figure3) the keys operated by the fingers of the left hand by one to the right. In this case, the little finger of the left hand will be responsible for operating the two keys. An exemplary keyboard arrangement supporting characters available through the use of dead keys is presented Electronics 2021, 10, x FOR PEER REVIEWasTab shown in Figure4. The location and number of dead keys vary from one to another 4 of 17

keyboard arrangement. Enter

Shift Shift Backspace Ctrl Alt Alt Ctrl Tab

Caps handling: Enter

Shift Little finger Shift

Ctrl Alt finger Alt Ctrl

KeyMiddle handling: finger

LittleIndex finger finger

Figure 2. Example of keyboardRing arrangement finger of ORK+ type with 10 letter keys. Middle finger In order to improve the ergonomics of typing, the authors propose an alternative to finger the illustrated arrangement of the characters of the ten-key ORK+ arrangement. The oper- ation of the letter keys in the arrangement presented in Figure 3 is the same as in touch FigureFigure 2. 2.Example Example of of keyboard keyboard arrangement arrangement of ORK+of ORK+ type type with with 10 letter 10 letter keys. keys. typing. In order to improve the ergonomics of typing, the authors propose an alternative to the illustrated arrangement of the characters of the ten-keyBackspace ORK+ arrangement. The oper- ation of the letter keys in the arrangement presented in Figure 3 is the same as in touch Tab typing. Caps Lock Enter Backspace Shift Shift Tab Ctrl Alt Alt Ctrl

Electronics 2021, 10, x FOR PEER REVIEWCaps Lock Enter 5 of 17 FigureFigure 3. 3.Alternative Alternative keyboard keyboard arrangement arrangement of ORK+ of ORK+ type with type 10 with keys. 10 keys. Shift Shift

Ctrl The ORK+Alt arrangements proposedAlt below Ctrlis shown on an alternative version of a

keyboard arrangement (Figure 3). The presented version of the keyboard layout allows to increaseFigure 3. Alternativethe maximum keyboard number arrangement of ORK+ of keys ORK+ to type twelve. with The10 keys. arrangement shown in Figure 2 limits the maximum number of keys for the ORK+ layout to eleven. In this paper, the The ORK+ arrangements proposed below is shown on an alternative version of a authors will focus only on the keys forming the ORK+; therefore, only those keys will be keyboard arrangement (Figure 3). The presented version of the keyboard layout allows to shownincrease in the illustrations maximum number presenting of ORK+ subsequent keys to twelve. arrangements. The arrangement In the case shown of thein Figure arrange- ments2 limits with the maximum11 letter keys, number the keyboardof keys for will the beOR extendedK+ layout byto eleven.one key, In locatedthis paper, directly the to theauthors right will side focus of the only key on operatedthe keys forming by the righthe ORK+;-hand therefore, little finger. only In those order keys to willbe able be to createshown an in ORK+ illustrations keyboard presenting with 12 subsequentkeys, it is ne arrangements.cessary to shift In (in the relation case of to the the arrange- one shown inments Figure with 3) 11the letter keys keys, operated the keyboard by the fingers will be ofextended the left byhand one by key, one located to the directly right. In to this case,the right the littleside offinger the keyof the operated left hand by thewill righ be t-handresponsible little finger.for operating In order the to twobe able keys. to An

exemplarycreate an ORK+ keyboard keyboard arrangement with 12 keys, supporting it is necessary characters to shift (in available relation tothrough the one theshown use of FiguredeadinFigure Figure 4.keys 4.Schematic Schematic3) is the presented keys presentation presentation operated as shown of keyboards byof keyboardsthein Figure fingers with two with4. of The dead the two location keys.left dead hand keys. and by numberone to the of right.dead Inkeys this vary fromcase, onethe littleto another finger keyboardof the left arrangement.hand will be responsible for operating the two keys. An exemplary2.2. Method keyboard of Developing arrangement ORK Keyboard supporting characters available through the use of dead Designationkeys is presented of the as ORKshown keyboard in Figure layout 4. The locationshould beand carried number out of indead accordance keys vary with fromthe following one to another steps: keyboard arrangement. 1. Determine the number of characters to be placed on the keyboard and the occurrence frequency of selected characters and their two-element combinations (). 2. Define the number of layout keys. 3. Determine the number and position of dead keys. 4. Select optimization criteria and their weights. 5. Assign characters to keys. The first step in building an ORK keyboard is to determine the number of characters to be placed on the keyboard. This number is strongly dependent, e.g., on the language for which the layout is designed and the number of letters present in it. Additionally, the number of characters to be arranged on the keyboard may be increased by extending the character set by e.g., numerical characters. In order to evaluate a given layout, frequency occurrence statistics of each character considered and their two-element combinations (bi- grams) are needed. The next step is to determine the number of keys that will be used on the keyboard. Based on the definition 1, the number of keys cannot be smaller than 8. At the same time, for ORK+ keyboards, the number of keys cannot exceed 12. The next step is to determine the number of dead keys. Assuming is the number of keys in the layout, each dead key increments that number by N. Due to a limited number of keys, all keyboards use dead keys to access subsequent letters of the . Due to the nature of dead keys, for characters assigned to them to be typed (after a single key- ), the next key needs to be a space. For example, the decimal point can be assigned to a dead key. In order to enter the decimal point, one needs to strike the dead key and then the space. The decimal point resulting will be with a space right after it. In this way, the result will be a character assigned to the dead key and a space. Therefore, the charac- ters assigned to dead keys should be those which are usually directly followed by a space. The characters that do not require access through the use of dead keys will be called de- fault characters. The number of dead keys depends on both the number of characters to be placed on the keyboard and on the number of keyboard keys. The maximum number of characters for a keyboard with N keys is N2 + N, assuming each key is a dead key. This limitation should be taken into account when specifying the number of keys and the num- ber of dead keys, with the assumed number of characters to be placed on the keyboard. The fourth step is to establish a list of criteria to be considered during the optimiza- tion process. In the examples presented in the following section, the authors used selected criteria of computer keyboard optimization provided in the study [2]. According to the authors, the most important and most frequently appearing criterion of keyboard optimi- zation in the literature is the alternation of typing, hence this criterion was used to opti- mize all proposed layouts. Another criterion used is the even use of each finger when

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2.2. Method of Developing ORK Keyboard Designation of the ORK keyboard layout should be carried out in accordance with the following steps: 1. Determine the number of characters to be placed on the keyboard and the occurrence frequency of selected characters and their two-element combinations (bigrams). 2. Define the number of layout keys. 3. Determine the number and position of dead keys. 4. Select optimization criteria and their weights. 5. Assign characters to keys. The first step in building an ORK keyboard is to determine the number of characters to be placed on the keyboard. This number is strongly dependent, e.g., on the language for which the layout is designed and the number of letters present in it. Additionally, the number of characters to be arranged on the keyboard may be increased by extending the character set by e.g., numerical characters. In order to evaluate a given layout, frequency occurrence statistics of each character considered and their two-element combinations (bigrams) are needed. The next step is to determine the number of keys that will be used on the keyboard. Based on the definition 1, the number of keys cannot be smaller than 8. At the same time, for ORK+ keyboards, the number of keys cannot exceed 12. The next step is to determine the number of dead keys. Assuming N is the number of keys in the layout, each dead key increments that number by N. Due to a limited number of keys, all keyboards use dead keys to access subsequent letters of the alphabet. Due to the nature of dead keys, for characters assigned to them to be typed (after a single keystroke), the next key needs to be a space. For example, the decimal point can be assigned to a dead key. In order to enter the decimal point, one needs to strike the dead key and then the space. The decimal point resulting will be with a space right after it. In this way, the result will be a character assigned to the dead key and a space. Therefore, the characters assigned to dead keys should be those which are usually directly followed by a space. The characters that do not require access through the use of dead keys will be called default characters. The number of dead keys depends on both the number of characters to be placed on the keyboard and on the number of keyboard keys. The maximum number of characters for a keyboard with N keys is N2 + N, assuming each key is a dead key. This limitation should be taken into account when specifying the number of keys and the number of dead keys, with the assumed number of characters to be placed on the keyboard. The fourth step is to establish a list of criteria to be considered during the optimization process. In the examples presented in the following section, the authors used selected criteria of computer keyboard optimization provided in the study [2]. According to the authors, the most important and most frequently appearing criterion of keyboard optimization in the literature is the alternation of typing, hence this criterion was used to optimize all proposed layouts. Another criterion used is the even use of each finger when typing. It should also be noted that some of the criteria in the literature related to e.g., minimizing the use of the bottom row and keyboard top row are fully realized by the ORK layout, since these rows are not used to input characters. The last step of the method is to arrange characters on the keyboard, taking into account the adopted restrictions. Depending on the chosen optimization criteria, this task can be performed using heuristic algorithms (e.g., hill climbing, tabu search, simulated annealing, genetic algorithms) or manually. Manual characters setting may be justified when the only criterion is to map another layout as accurately as possible and transform it into an ORK layout. A mixed approach is also possible—some characters (especially non-letter characters) are set manually, while others are optimized. The presented method of creating ORK keyboards was used to create several types of keyboards dedicated to the . In the next section, few examples of ORK+ type keyboards are proposed. Electronics 2021, 10, x FOR PEER REVIEW 6 of 17

typing. It should also be noted that some of the criteria in the literature related to e.g., minimizing the use of the bottom row and keyboard top row are fully realized by the ORK layout, since these rows are not used to input characters. The last step of the method is to arrange characters on the keyboard, taking into ac- count the adopted restrictions. Depending on the chosen optimization criteria, this task can be performed using heuristic algorithms (e.g., hill climbing, tabu search, simulated annealing, genetic algorithms) or manually. Manual characters setting may be justified when the only criterion is to map another layout as accurately as possible and transform it into an ORK layout. A mixed approach is also possible—some characters (especially non-letter characters) are set manually, while others are optimized. The presented method of creating ORK keyboards was used to create several types of keyboards dedicated to the English language. In the next section, few examples of ORK+ type keyboards are proposed.

3. ORK Type Keyboards Electronics 2021, 10, 663 6 of 17 In this part of the study, the authors proposed some examples of ORK type key- boards. The proposed keyboards have been divided into groups, and each group will be presented in the following subsections. The keyboards presented below were tested using 3. ORK Type Keyboards the Keyboard Layout Creator [32]. Thus, the use of ORK layouts does not requireIn this additional part of the software study, the authorsor dedicated proposed driv someers. examples The occurrence of ORK type frequency keyboards. statistics of The proposed keyboards have been divided into groups, and each group will be presented inthe the letters following and subsections.bigrams in English The keyboards were used presented to arrange below wereletters tested on the using keyboards the Mi- [33]. Each crosoftarrangement Keyboard will Layout be named Creator according [32]. Thus, to the the use following of ORK layoutspattern: does the not name require of the arrange- additionalment—the software name orof dedicated the group drivers. of arrangements—the The occurrence frequency type statistics of the ofarrangement the letters (ORK or andORK+). bigrams All inarrangements English were usedwere to developed arrange letters using on thethe keyboards random-restart [33]. Each iterative arrange- hill climbing mentalgorithm. will be named according to the following pattern: the name of the arrangement—the name of the group of arrangements—the type of the arrangement (ORK or ORK+). All arrangements were developed using the random-restart iterative hill climbing algorithm. 3.1. VX-ORK+ Arrangement Group 3.1. VX-ORK+The key Arrangementfeature of the Group VX-ORK+ group keyboard is as follows: ten letter keys, two of whichThe are key dead feature keys. of the VX-ORK+ group keyboard is as follows: ten letter keys, two of whichThe are deadfirst keys.proposed VX-ORK+ type keyboard is one of the possible QWERTY repre- The first proposed VX-ORK+ type keyboard is one of the possible QWERTY repre- sentations. The A-VX-ORK+ keyboard was developed by assigning the middle QWERTY sentations. The A-VX-ORK+ keyboard was developed by assigning the middle QWERTY rowrow toto the the default default characters. characters. There There are dead are keysdead located keys located in the locations in the oflocations letters “” of letters “F” and “J”, “J”, with with the the full stop “.” and“.” commaand “,” characters “,” characters assigned, assigned, respectively. respectively. The letters The letters “F”“F” and and “J” “J” are are assigned assigned to the to full the stop full and stop comma and comma keys on thekeys QWERTY on the QWERTY keyboard. The keyboard. The A-VX-ORK+A-VX-ORK+ arrangement arrangement is presented is presented in Figure in 5Figure. 5.

A S , . ;

G

Q E R U I P

T

Z X F J /

B N

Figure 5. 5.A-VX-ORK+ A-VX-ORK+ arrangement. arrangement.

DeadDead keys keys are are assigned assigned to theto the keys keys operated operated by the by index the index fingers fingers due to thedue low to the low fre- frequency of occurrence of the letters “F” and “J” assigned to these keys in the QWERTY arrangement.quency of occurrence Since the authors’ of the objectiveletters “F” is to and arrange “J” theassigned dead keys to symmetrically,these keys in thethe QWERTY pairarrangement. of letters was Since selected the authors’ with the lowestobjective total is frequency. to arrange It isthe important, dead keys because symmetrically, all the of the characters, except the default ones, need two keys to be typed (a dead key + the character key). For this reason, the most frequent characters should be selected as defaults. The presented assignment of the QWERTY arrangement row to the specified dead key aims at increasing the usage frequency of the fingers of both hands during typing (a finger of one hand strikes a dead key, a finger of the other is responsible for typing the character). The second proposed VX-ORK+ type keyboard (Figure6) is also the QWERTY key- board adaptation. The default keys of the -VX-ORK+ keyboard form the first row of the QWERTY keyboard. Due to the assignment of dead keys to “Q” and “P” keys on the QWERTY keyboard, the letters “Q” and “P” are assigned to the “,” and “.” keys on the QWERTY keyboard. Electronics 2021, 10, x FOR PEER REVIEW 7 of 17

pair of letters was selected with the lowest total frequency. It is important, because all of the characters, except the default ones, need two keys to be typed (a dead key + the char- acter key). For this reason, the most frequent characters should be selected as defaults. The pre- sented assignment of the QWERTY arrangement row to the specified dead key aims at increasing the usage frequency of the fingers of both hands during typing (a finger of one hand strikes a dead key, a finger of the other is responsible for typing the character). The second proposed VX-ORK+ type keyboard (Figure 6) is also the QWERTY key- board adaptation. The default keys of the Q-VX-ORK+ keyboard form the first row of the QWERTY keyboard. Due to the assignment of dead keys to “Q” and “P” keys on the Electronics 2021, 10, 663 7 of 17 QWERTY keyboard, the letters “Q” and “P” are assigned to the “,” and “.” keys on the QWERTY keyboard.

, W E R U I O .

T Y

A S D F J K L ;

G H

Z X C V M Q P /

B N

FigureFigure 6. 6.Q-VX-ORK+ Q-VX-ORK+ arrangement. arrangement.

TheThe default default characters characters of the of Q-VX-ORK+ the Q-VX-ORK+ arrangement arrangement are in the are first in row the of first the row of the QWERTY keyboard, due to the high prevalence of the letters. Dead keys are located on QWERTY keyboard, due to the high prevalence of the letters. Dead keys are located on the keys operated by little fingers, because of the low prevalence of the letters “Q” and “P”,the whichkeys areoperated moved by to makelittle spacefingers, for thebecause dead keys.of the The low location prevalence of the dead of the keys letters is “Q” and also“P”, based which on are the researchmoved byto make Dvorak space and Dealey for the [2 ],dead according keys. toThe which location typing of in the the dead keys is directionalso based from on the the little research finger to by the Dvorak index finger and is Dealey more convenient [2], according than in theto which opposite typing in the direction.direction The from assignment the little of finger the rows to tothe the index dead keysfinger was is chosenmore convenient so as to maximize than thein the opposite totaldirection. prevalence The of assignment the letters that of arethe typed rows using to the fingers dead of keys both was hands. chosen so as to maximize the The last of the proposed keyboards, the VX-ORK+ type one, is the P-VX-ORK+ ar- rangement.total prevalence The keyboard of the has letters been that developed are typed on the using basis offingers the results of both of calculations hands. for the followingThe last function: of the proposed keyboards, the VX-ORK+ type one, is the P-VX-ORK+ ar- rangement. The keyboard has been developed on the basis of the results of calculations   + ∗ + ∗ for the followingF-VX-ORK function:: max ∑l∈letters xl wl ∑b∈bigrams yb wb , (1)

where letters denote theF-VX-ORK+: set of all of max the letters∑∈ of the𝑥 English∗𝑤 + alphabet,∑∈bigrams𝑦 ∗𝑤denote, (1) the set of all bigrams, w and w denote the frequency of a given letter and given , where letters denotel the setb of all of the letters of the English alphabet, bigrams denote the respectively, while xl and yb are binary variables defined as follows: set of all bigrams, wl and wb denote the frequency of a given letter and given bigram, re-  0 if theletter is not a default character spectively, whilex xl= and yb are binary variables defined as follows:, (2) l 1 if the letter is a default character 0 𝑖𝑓 𝑡ℎ𝑒 𝑙𝑒𝑡𝑡𝑒𝑟 𝑖𝑠 𝑛𝑜𝑡 𝑎 𝑑𝑒𝑓𝑎𝑢𝑙𝑡 𝑐ℎ𝑎𝑟𝑎𝑐𝑡𝑒𝑟 𝑥 = , (2)  0 if the bigram1 𝑖𝑓 is 𝑡ℎ𝑒 typed 𝑙𝑒𝑡𝑡𝑒𝑟 with fingers of 𝑖𝑠 one hand𝑎 𝑑𝑒𝑓𝑎𝑢𝑙𝑡 𝑐ℎ𝑎𝑟𝑎𝑐𝑡𝑒𝑟 yb = . (3) 1 if0 the 𝑖𝑓 bigram 𝑡ℎ𝑒 is typed𝑏𝑖𝑔𝑟𝑎𝑚 with fingers 𝑖𝑠 of𝑓 𝑡𝑦𝑝𝑒𝑑𝑤𝑖𝑡ℎ both𝑖𝑛𝑔𝑒𝑟𝑠 hands 𝑜𝑓 𝑜𝑛𝑒 ℎ𝑎𝑛𝑑 𝑦 = . (3) In the case of bigrams, 1 it 𝑖𝑓 was 𝑡ℎ𝑒 only 𝑏𝑖𝑔𝑟𝑎𝑚 verified whether 𝑖𝑠 there 𝑡𝑦𝑝𝑒𝑑𝑓 𝑤𝑖𝑡ℎ 𝑖𝑛𝑔𝑒𝑟𝑠 is a switch of the𝑜𝑓 hands 𝑏𝑜𝑡ℎ ℎ𝑎𝑛𝑑𝑠 between the first and the second letter typed. No account was taken of whether the letter not beingIn the a default case characterof bigrams, is typed it was with only the fingers verified of thewhether same hand there (such is a cases switch were of the hands takenbetween into account the first in and the first the component second letter of the typed. sum constituting No account the F-VX-ORK+was taken function).of whether the letter Thenot objectivebeing a behinddefault including character this is componenttyped with in th thee fingers F-VX-ORK+ of the function same hand (1) was (such to cases were maximizetaken into alternating account typing. in the According first component to certain of research the sum [2,5], constituting alternating typing the F-VX-ORK+ is one func- oftion). the key The factors objective that increases behind theincluding typing speed this andcomponent decreases in the the number F-VX-ORK+ of errors. function (1) was Based on the function presented, six-letter sets were developed—three for each corre- sponding hand: • a set of letters assigned to default characters, • a set of letters using dead keys which need to be typed with both hands (the dead key is operated by a different hand than the character to be typed), • a set of letters using dead keys for which both the dead key and the letter key are operated with fingers of the same hand. Electronics 2021, 10, x FOR PEER REVIEW 8 of 17

to maximize alternating typing. According to certain research [2,5], alternating typing is one of the key factors that increases the typing speed and decreases the number of errors. Based on the function presented, six-letter sets were developed—three for each cor- responding hand: • a set of letters assigned to default characters, • a set of letters using dead keys which need to be typed with both hands (the dead key is operated by a different hand than the character to be typed), Electronics 2021, 10, 663 • a set of letters using dead keys for which both the dead key and the8 of 17letter key are operated with fingers of the same hand. Based on the distribution obtained, the letters are assigned to the keys according to Based on the distribution obtained, the letters are assigned to the keys according to the following criteria: the following criteria: • • maximizingmaximizing the the even even distribution distribution of typing of loadtyping on individualload on individual fingers, fingers, •• minimizingminimizing the the usage usage frequency frequency for a single for a finger single operating finger operating two consecutive two consecutive keys. keys. TheThe calculations calculations resulted resulted in the in keyboard the keyboa arrangementrd arrangement presented presented in Figure7. in Figure 7.

, A E O S T N .

I R

P X Q M C L V

Z F

U Y K W D H G

J B

FigureFigure 7. 7.P-VX-ORK+ P-VX-ORK+ arrangement. arrangement.

The keyboards of the VX-ORK+ group allow for the typing of up to 30 characters, The keyboards of the VX-ORK+ group allow for the typing of up to 30 characters, including 28 letters (due to the location of the two dead keys). In the authors’ opinion, VX-ORK+including type 28 keyboardsletters (due are to best the characterized location of by the the two following dead twokeys). values: In the the authors’ frequency opinion, VX- ofORK+ typing type bigrams keyboards with fingers are of best both characterized hands (BI), and by the the prevalence following of letters two assignedvalues: tothe frequency theof defaulttyping charactersbigrams with (DK—default fingers key).of both The hands higher (BI), the DK and value, the prevalence the lower the of value letters assigned Keystrokesto the default per Character characters (KSPC) (DK—default [34]. For all key). ORK The keyboards, higher thethe KSPC DK value, value isthe in lower the the value rangeKeystrokes [1;2]. The per first Character value measures (KSPC) the [34]. presence For ofall alternating ORK keyboards, typing and the it shouldKSPC bevalue is in the maximized to the fully alternating typing. The second value measures the frequency of lettersrange typed [1;2]. with The just first one value strike, meas withoutures using the a presence dead key; alsoof alternating here: the higher typing the value, and it should be themaximized better the arrangement.to the fully Tablealternating1 presents typing. the values The ofsecond both metrics value for measures the VX-ORK+ the frequency of groupletters arrangements. typed with just one strike, without using a dead key; also here: the higher the value, the better the arrangement. Table 1 presents the values of both metrics for the VX-ORK+ Tablegroup 1. Assessment arrangements. of VX-ORK+ group arrangements. ASD Q P Table 1. AssessmentBI of VX-ORK+ 56.84% group arrangements. 53.13% 76.23% DK 29.90% 49.33% 65.04% ASD Q P The resultsBI presented reveal that, against56.84% the metric proposed53.13% by the authors, by far76.23% the best of the arrangementsDK analyzed is29.90% P-VX-ORK+, for which:49.33% 65.04% • more than three-quarters of the bigrams are typed alternatingly, • theThe letters results assigned presented to default reveal characters that, against account th fore nearlymetric two proposed thirds of by all the of theauthors, by far the lettersbest of typed; the arrangements only slightly more anal thanyzed one-third is P-VX-ORK+, of the characters for which: typed require the use of a dead key, that is, the use of two keys to type a single character. • more than three-quarters of the bigrams are typed alternatingly, The other two arrangements’ alternating ratios (BI) are close to each other. A clear dif- ference is noticeable for the DK metric; the value obtained for the Q-VX-ORK+ arrangement is definitely better.

3.2. W-ORK+ Arrangement Group The keyboards of the W-ORK+ group have the following structure: eleven letter keys, including ten dead keys. Electronics 2021, 10, x FOR PEER REVIEW 9 of 17

• the letters assigned to default characters account for nearly two thirds of all of the letters typed; only slightly more than one-third of the characters typed require the use of a dead key, that is, the use of two keys to type a single character. The other two arrangements’ alternating ratios (BI) are close to each other. A clear difference is noticeable for the DK metric; the value obtained for the Q-VX-ORK+ arrange- ment is definitely better.

3.2. W-ORK+ Arrangement Group

Electronics 2021, 10, 663 The keyboards of the W-ORK+ group have the following structure: eleven9 of 17letter keys, including ten dead keys. The W-ORK+ keyboards proposed by the authors achieve a very high alternating ra- tio The(BI), W-ORK+ up to 100%, keyboards which proposed is possible by the thanks authors to achieve the use a very of numero high alternatingus (in the ratio cases pre- (BI),sented, up to at 100%, least which ten) dead is possible keys, thanksand to to assigning the use of a numerous given character (in the casesto two presented, keys on the key- atboard, least ten) so that dead a keys, given and character to assigning may a be given typed character (preceded to two by keys a dead on the key) keyboard, with any of the sohands. that a givenThe example character of may an ABC-W-ORK+ be typed (preceded arrang by aement dead key)presented with any here of theis based hands. on the al- Thephabetical example oforder an ABC-W-ORK+ and comprises arrangement eleven letter presented keys here(including is based ten on thedead alphabetical keys); it is shown orderin Figure and comprises 8. eleven letter keys (including ten dead keys); it is shown in Figure8.

. ! ; , , ; ! . Z

? ?

A B C D D C B A Z

E E

F G H I I H G F Z

J J

K L M N N M L K Z

O O

P Q R S S R Q P Z

T T

U V W X X W V U Z

Y Y

FigureFigure 8. 8.ABC-W-ORK+ ABC-W-ORK+ arrangement. arrangement.

TheThe example example of theof the ABC-W-ORK+ ABC-W-ORK+ arrangement arrangement shows shows what the what authors the believesauthors tobelieves to bebe the the key key feature feature of theof the proposed proposed W-ORK+ W-ORK+ arrangement arrangement group: group: both all both the character all the character keys (save the letter “Z” character) and the dead keys are arranged so that half of the keys (save the letter “Z” character) and the dead keys are arranged so that half of the arrangement (let us, say, to the left of the vertical axis) is as a mirror image of the other half. Therefore,arrangement each letter(let us, (with say, the to exception the left of of the “Z”), ve canrtical be typedaxis) byis as any a ofmirror the hands. image Such of the other arrangementhalf. Therefore, has the each following letter (with property: the exception any specific of character“Z”), can is be assigned typed by to theany same of the hands. finger,Such whicheverarrangement of the has two the hands following is typing property: it. any specific character is assigned to the sameIn finger, the ABC-W-ORK+ whichever of arrangements, the two hands all theis typing letters it. (except for the letter “Z”) are assigned to dead keys. The objective of this solution is to maximize alternating ratio (BI), which is equal to 100% in the example described. The high BI value was obtained at the expense of DK, which for the ABC-W-ORK+ arrangement is slightly over 0 (only the letter “Z” is assigned to default character, while its prevalence is approximately 0.1%). This means that typing of practically every letter requires the use of two keys. Another arrangement presented is the Q-W-ORK+ arrangement. The arrangement is developed based on the QWERTY arrangement. All letters, except for “N” and “M”, are arranged in a manner similar to the QWERTY arrangement. For the Q-W-ORK+ Electronics 2021, 10, x FOR PEER REVIEW 10 of 17

In the ABC-W-ORK+ arrangements, all the letters (except for the letter “Z”) are as- signed to dead keys. The objective of this solution is to maximize alternating ratio (BI), which is equal to 100% in the example described. The high BI value was obtained at the expense of DK, which for the ABC-W-ORK+ arrangement is slightly over 0 (only the letter “Z” is assigned to default character, while its prevalence is approximately 0.1%). This means that typing of practically every letter requires the use of two keys. Electronics 2021 10 , , 663 Another arrangement presented is the Q-W-ORK+ arrangement. The arrangement10 of 17 is developed based on the QWERTY arrangement. All letters, except for “N” and “M”, are arranged in a manner similar to the QWERTY arrangement. For the Q-W-ORK+ arrange- arrangement,ment, the BI theratio BI is ratio 100%. is 100%. For comparison, For comparison, for forthe the standard standard QWERTY, QWERTY, BI is merelymerely 52.87%. 52.87%.The Q-W-ORK+ The Q-W-ORK+ arrangement arrangement is shown is shown in Figure in Figure 9.9 .

. ! ; , , ; ! . M

? ?

Q W E R R E W Q M

T T

A S D F F D S A M

G G

Z X C V V C X Z M

B B

P O I U U I O P M

Y Y

N L K J J K L N M

H H

FigureFigure 9. 9.Q-W-ORK+ Q-W-ORK+ arrangement. arrangement.

InIn the the W-ORK+ W-ORK+ arrangements arrangements presented presented here, the here arrangement, the arrangement of letters is not of optimized.letters is not opti- Themized. arrangements The arrangements presented herein presented below are herein optimized below against are optimized the following against function: the following function:     + ∗ − + ∗ F-W-ORK : min ∑ f ∈ f ingers ∑l∈letters x f l wl o ∑l∈letters zl wl , (4) F-W-ORK+: min∑∈∑∈ 𝑥 ∗𝑤−𝑜+ ∑∈ 𝑧 ∗𝑤, (4) where letters denotes the set of all letters in the English alphabet, fingers denotes the set ofwhere fingers letters of one denotes hand, excluding the set of the all thumbletters (thein the assignment English alphabet, of characters fingers to both denotes hands the set of isfingers identical), of onewl denoteshand, excluding the given the letter’s thumb prevalence, (the assignment the o parameter of characters is the expected to both hands is averageidentical), value w ofl denotes the load the toeach given of letter’s the fingers, prevalence, while xfl and thez ol areparameter binary variables is the expected defined average asvalue follows: of the load to each of the fingers, while xfl and zl are binary variables defined as  0 if the letter l is not typed with finger f follows: x = , (5) f l 1 if the letter l is typed with finger f 0 𝑖𝑓 𝑡ℎ𝑒 𝑙𝑒𝑡𝑡𝑒𝑟 𝑙 𝑖𝑠 𝑛𝑜𝑡𝑓 𝑡𝑦𝑝𝑒𝑑𝑤𝑖𝑡ℎ 𝑖𝑛𝑔𝑒𝑟 𝑓  0 if entering𝑥 the= letter does not require movement of the index finger, (5) z = 1 𝑖𝑓 𝑡ℎ𝑒 𝑙𝑒𝑡𝑡𝑒𝑟 𝑙 𝑖𝑠𝑓 𝑡𝑦𝑝𝑒𝑑𝑤𝑖𝑡ℎ 𝑖𝑛𝑔𝑒𝑟 𝑓 . (6) l 1 if entering the letter requires movement of the index finger The value of the parameter o is calculated using the following formula:

o = 2 × (100% − wd)/4, (7)

where wd is the frequency of the default character on a W-ORK+ keyboard. The parameter o is used to determine what should be the frequency of the letters typed with a given finger (four fingers of the hand are used for typing), assuming that every letter, except the letter assigned to the default character, requires two fingers (striking two keys). Electronics 2021, 10, x FOR PEER REVIEW 11 of 17

𝑧 = 0 𝑖𝑓 𝑒𝑛𝑡𝑒𝑟𝑖𝑛𝑔 𝑡ℎ𝑒 𝑙𝑒𝑡𝑡𝑒𝑟 𝑑𝑜𝑒𝑠 𝑛𝑜𝑡 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑒𝑥 𝑚𝑜𝑣𝑒𝑚𝑒𝑛𝑡𝑜𝑓𝑡ℎ𝑒𝑖𝑛𝑑 𝑓𝑖𝑛𝑔𝑒𝑟 (6) . 1 𝑖𝑓 𝑒𝑛𝑡𝑒𝑟𝑖𝑛𝑔 𝑡ℎ𝑒 𝑙𝑒𝑡𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑠𝑓 𝑚𝑜𝑣𝑒𝑚𝑒𝑛𝑡𝑜𝑓𝑡ℎ𝑒𝑖𝑛𝑑𝑒𝑥 𝑖𝑛𝑔𝑒𝑟 The value of the parameter o is calculated using the following formula:

𝑜 = 2 × (100% −𝑤 )/4, (7)

where wd is the frequency of the default character on a W-ORK+ keyboard. The parameter o is used to determine what should be the frequency of the letters typed with a given finger (four fingers of the hand are used for typing), assuming that Electronics 2021, 10, 663 11 of 17 every letter, except the letter assigned to the default character, requires two fingers (strik- ing two keys). The load to the little finger of the right hand associated with typing the default character is neglected. The load to the little finger of the right hand associated with typing the default character Optimization against the function defined above is designed to ensure even distribu- is neglected. tionOptimization of loads to all against of the the typing function fingers defined (the above first is addend), designed toas ensure well as even to distri-minimize the fre- butionquency of loadsof the to index all of thefinger typing movements fingers (the (the first second addend), addend). as well as The to minimize function the omits the de- frequencyfault character of the indexselected finger arbitrarily. movements (the second addend). The function omits the defaultBased character on selectedthe presented arbitrarily. function (F-W-ORK+ (4)), the My-W-ORK+ and U-W-ORK+ keyboardsBased on were the presented developed. function The (F-W-ORK+main difference (4)), the between My-W-ORK+ them and is in U-W-ORK+ the letter assigned to keyboards were developed. The main difference between them is in the letter assigned the default character. For My-W-ORK+ arrangement, it is the letter “Z”, while for the U- to the default character. For My-W-ORK+ arrangement, it is the letter “Z”, while for theW-ORK+ U-W-ORK+ arrangement, arrangement, it is it isthe the letter letter “E”. “E”. Th Thee otherother differences differences result result from from this this assign- assignmentment because because the change the change in the in the default default charac characterter changes changes the the input input data forforthe the optimizing optimizingfunction. function. FigureFigure 10 10presents presents the My-W-ORK+the My-W-ORK+ arrangement. arrangement.

. ! ; , , ; ! . Z

? ?

C E U T T U E C Z

B B

P N R H H R N P Z

Y Y

I D O A A O D I Z

G G

S F L M M L F S Z

J J

V W X K K X W V Z

Q Q

FigureFigure 10. 10.My-W-ORK+ My-W-ORK+ arrangement. arrangement.

TheThe My-W-ORK+ My-W-ORK+ arrangement arrangement is characterized is characterized by a load practically by a load evenly practically distributed evenly distrib- among all typing fingers. The difference between the most and least loaded fingers is 0.1%. Statistically,uted among the all My-W-ORK+ typing fingers. arrangement The difference requires the between index finger the most movement and least only forloaded fingers oneis 0.1%. in twenty-two Statistically, clicks. the My-W-ORK+ arrangement requires the index finger movement onlyAnother for one presented in twenty-two arrangement clicks. is the W-U-ORK+ one. Its characteristic feature is the assignment of letter “E” to the default character. This allowed to obtain the DK ratio of 12.5%. The U-W-ORK+ arrangement is presented in Figure 11.

Electronics 2021, 10, x FOR PEER REVIEW 12 of 17

Electronics 2021, 10, 663 Another presented arrangement is the W-U-ORK+ one. Its characteristic12 offeature 17 is the assignment of letter “E” to the default character. This allowed to obtain the DK ratio of 12.5%. The U-W-ORK+ arrangement is presented in Figure 11.

FigureFigure 11. 11.U-W-ORK+ U-W-ORK+ arrangement. arrangement.

TheThe U-W-ORK+ U-W-ORK+ arrangement, arrangement, like the like previous the previo one, ensuresus one, almost ensures evenly almost distributed evenly distrib- loadsuted toloads all typing to all typing fingers. fingers. In the caseIn the of case the U-W-ORK+ of the U-W-ORK+ arrangement, arrangement, the difference the difference betweenbetween the the most most and and least least loaded loaded fingers fingers is 2‰. is In 2‰. addition, In addition, the index the finger index movement finger movement frequency decreased to 3.6%. The greatest downside of the U-W-ORK+ arrangement is the frequency decreased to 3.6%. The greatest downside of the U-W-ORK+ arrangement is the big load to the right little finger, responsible for operating the key with the letter “E”. bigTable load2 to presents the right the little values finger, of the responsible BI and DK metrics for operating for the W-ORK+. the key with It also the shows letter “E”. the valuesTable of two2 presents additional the metrics values based of the on BI the and function DK metrics F-W-ORK+: for the load W-ORK+. distribution It toalso shows typingthe values fingers of (EL) two and additional the movement metrics frequency based foron thethe index function finger F-W-ORK+: while typing load a single distribution letterto typing (M). Both fingers of the (EL) metrics and proposed the movement refer to typing frequency a single for character the index (special finger characters while typing a notsingle included) letter requiring(M). Both two of keystrokes.the metrics The proposed table shows refer the to valuestyping of a thesingle metrics character for a (special singlecharacters keystroke not (EL/2,included) M/2). requiring two keystrokes. The table shows the values of the met- rics for a single keystroke (EL/2, M/2). Table 2. Assessment of the W-ORK+ group arrangements.

Table 2. Assessment of ABCthe W-ORK+ group Q arrangements. MY U BI 100.00%ABC 100.00%Q 100.00%MY 100.00% U DK 0.00% 2.51% 0.00% 12.49% EL/2BI 38.37%100.00% 20.71%100.00% 0.09%100.00% 0.01% 100.00% M/2DK 19.30%0.00% 18.20%2.51% 4.46%0.00% 3.56% 12.49% EL/2 38.37% 20.71% 0.09% 0.01% OnlyM/2 for U-W-ORK+ the19.30% DK ratio is more18.20% than 10%. While it enables4.46% the frequency3.56% of the characters requiring the use of two keys to be reduced, it also puts a large load to the littleOnly finger for of U-W-ORK+ the right hand. the AllDK of ratio the keyboards is more than from 10%. the W-ORK+ While it group enables are the fully frequency alternating. It should also be emphasized that all W-ORK + keyboards are fully alternating of the characters requiring the use of two keys to be reduced, it also puts a large load to for each language that contains the same letters as English. the little finger of the right hand. All of the keyboards from the W-ORK+ group are fully

Electronics 2021, 10, x FOR PEER REVIEW 13 of 17

alternating. It should also be emphasized that all W-ORK + keyboards are fully alternating for each language that contains the same letters as English. Electronics 2021, 10, 663 The indicator of even load to the fingers typing is by far the smallest13 of 17 in the case of optimized keyboards. In terms of the EL ratio, the worst is ABC-W-ORK+, for which the ratio is twice as high as for the Q-W-ORK+ arrangement. In terms of the movement of the indexThe finger, indicator the of values even load obtained to the fingers for the typing ABC-W-ORK+ is by far the smallestand Q-W-ORK+ in the case arrangements of are optimizedsimilar, but keyboards. differ Insignificantly terms of the ELfrom ratio, the the values worst is obtained ABC-W-ORK+, for the for My-W-ORK+ which the and U-W- ratio is twice as high as for the Q-W-ORK+ arrangement. In terms of the movement of ORK+ arrangements. the index finger, the values obtained for the ABC-W-ORK+ and Q-W-ORK+ arrangements are similar, but differ significantly from the values obtained for the My-W-ORK+ and U-W-ORK+3.3. NUM-ORK+ arrangements. Arrangement

3.3. NUM-ORK+The last of Arrangement the presented arrangement is the NUM-ORK+ keyboard. The NUM-ORK+ arrangementThe last of the uses presented 11 keys, arrangement where all is thekeys NUM-ORK+ are dead keyboard.keys. An The additional NUM-ORK+ key was assigned arrangementto the location uses 11of keys,the default where all character. keys are dead This keys. enabled An additional typing key digits, was assigned the access to which is toprovided the location with of the the default additional character. dead This key. enabled Howeve typingr, digits,for the the same access reason, to which the is keyboard is no providedlonger 100% with the alternating. additional dead Some key. of However, the occurrences for the same of reason, the letter the keyboard “Z” will is norequire using the longersame 100%hand alternating. twice. This Some will of take the occurrences place when of thethe letter left hand “Z” will ends require typing using the the letter preceding same hand twice. This will take place when the left hand ends typing the letter preceding thethe letter letter “Z”. “Z”. Then, Then, the left the hand left shouldhand beshould used againbe used or the again right handor the should right be hand used should be used twice.twice. The The NUM-ORK+ NUM-ORK+ arrangement arrangement presented presented in Figure 12in is Figure developed 12 is on developed the basis of on the basis of My-W-ORK+.My-W-ORK+.

. ! ; , , ; ! . :

? ?

C E U T T U E C Z

B B

P N R H H R N P Z

Y Y

I D O A A O D I Z

G G

S F L M M L F S Z

J J

V W X K K X W V Z

Q Q

1 2 3 4 7 8 9 0 @

5 6

FigureFigure 12. 12.NUM-ORK+ NUM-ORK+ arrangement. arrangement.

An unquestionable advantage of the NUM-ORK+ is supporting typing digits. How- ever, with an additional dead key, the keyboard is no longer fully alternating. Addition- ally, accessing digits assigned to the right hand requires the same hand to be used repeat- edly (twice).

Electronics 2021, 10, 663 14 of 17

An unquestionable advantage of the NUM-ORK+ is supporting typing digits. However, with an additional dead key, the keyboard is no longer fully alternating. Additionally, access- ing digits assigned to the right hand requires the same hand to be used repeatedly (twice).

4. Discussion On the basis of the method for developing ORK keyboard, several examples of ORK+ keyboard layouts were created and presented in Section3. The proposed layouts were divided into three groups, each of which was characterized by different assumptions and was aimed at showing various possibilities of using ORK layouts. Layouts of the first group (VX-ORK+) use the fewest number of keys and have the lowest number of dead keys. Consequently, they can be considered the easiest to learn as they do not require a key combination to enter eight letters. Additionally, the A and Q layouts reflect the most popular keyboard layout—QWERTY. This aspect may additionally affect the ease of use of layouts by people use the QWERTY layout on a daily basis. The last layout of this group (P-VX-ORK+) has been optimized in order to maximize the frequency of using letters, the typing of which does not require the use of a key combination (DK), and also to maximize the alternation of typing (BI). Layouts belonging to the second group (W-ORK+) have a larger number of keys than the VX-ORK+ layouts. By increasing the number of keys and the number of dead keys, it was possible to achieve full alternation of typing (BI = 100%). At the same time, it caused the DK metric to drop to a very low level. In the U-W-ORK+ keyboard, for which this metric reaches the highest value (DK = 12.5%), it is necessary to make frequent movements with the little finger (supporting the letter “E”). The example of the Q-W-ORK+ layout shows the possibility of adapting the QWERTY keyboard to a fully alternating layout. A fully alternating version of the alphabetic keyboard (ABC-W-ORK +) was also proposed. The last layout group presented (NUM-ORK+), consisting of 11 keys, all of which are dead keys, contains numerical characters. This arrangement is not fully alternating (some occurrences of the letter “Z” will require using the fingers of the same hand twice), but it contains as much as 11 characters more than the layouts of the W-ORK+ group. By adding another key, it would be possible to obtain the effect of full alternation also for this layout. The presented examples of layouts differ in the number of keys, dead keys, as well as the criteria for arranging characters. As presented in the study, the results of individual evaluation criteria strongly depend on the layout parameters mentioned. According to the authors, comparing different layouts such as ORK or ORK+ makes sense only when the number of keys, dead keys, and characters to appear on the keyboard are equal. The requirements for the layout must also be similar, e.g., whether the layout should be as similar as possible to the most common QWERTY keyboard, or whether it should be optimized for selected criteria. Therefore, comparing the results for the groups of layouts presented in the study, could suggest incorrect conclusions regarding the individual layouts. All the presented layouts serve only to illustrate the wide possibilities of the ORK+ keyboards.

5. Conclusions The idea behind the ORK type keyboards proposed by the authors is to decrease the number of the movements of the fingers when typing, through the development of keyboards with keys arranged in one row. In order to enable the use of the same keyboard on computers and mobile devices, the authors proposed the ORK+ solution. ORK+ key- boards consist of a smaller number of keys, as compared to conventional keyboards (e.g., those compliant with the ISO/IEC 9995-2:2009 standard [31]). The arrangements proposed reduce the number of finger movements, since only the index and little fingers operate two keys each, while the middle and ring fingers operate only one key each, which means that the vertical movements of these fingers are eliminated. The reduction of the number of ‘character’ keys has made it necessary to introduce dead keys, which in turn renders it difficult to access some letters. The difficulty consists in a need to use two keystrokes Electronics 2021, 10, 663 15 of 17

to type a single letter (KSPC = 2). It is more difficult, and for the W-ORK+ arrangements impossible, to label each key with the characters it provides easy access to. The idea of using the key combination to enter a single character, presented in this study, can also be used for very small devices, such as smartwatches. The topic of small devices keyboards is the subject of many studies (e.g., [35–38]) and this topic still very current. Therefore, ORK+ arrangements require more detailed learning than as in the case of the QWERTY arrangement does, because typing some letters is more complicated. The downside can, however, prove to be an advantage of the ORKs+ arrangements, because the use of an ORK+ keyboard practically must be preceded by learning it. There is no such need in the case of the QWERTY keyboard. This, however, may contribute to less effective typing, such as typing with the index finger only or ‘searching for letters’ on the keyboard. In addition to minimizing the number of finger movements, the W-ORK+ group keyboards have another important feature: they support fully alternating typing. This feature is commonly listed among most important optimization criteria for the arrangement of characters on the keyboard. Additionally, W-ORK+ group keyboards are fully alternating for any language that contains the same letters as English. ORK+ also eliminates the need to use more than one row for writing. Thus, it imple- ments the criterion of minimizing the frequency of using the upper and the lower rows of the keyboard for typing. In addition, movements across the home row are completely eliminated. In the case of the W-ORK+ group, the need to enter two consecutive characters using the same finger is also eliminated. By adding one more key (to 12 keys), it would possible to add letters that are characteristic for a given language. This would create a universal (for any Latin-based language) keyboard, in which the location of all non-diacritical letters would be fixed. ORK+ type keyboards are more difficult to use than the existing keyboards. They have, however, some major advantages, among which a decreased number of finger movements, and, in the case of the W-ORK+ arrangements, fully alternating typing have to be emphasized. Another important advantage is the significant reduction in the number of keys required on the keyboard, which enables the design of smaller keyboards. This is important in view of the fact that ORK+ keyboards are designed for the use also in small mobile devices.

Author Contributions: Conceptualization, R.P.; methodology, R.P.; software, R.P. and J.D.; validation, R.P. and P.Ł.; formal analysis, R.P., P.Ł. and J.D.; writing—original draft preparation, R.P., P.Ł. and J.D.; writing—review and editing, R.P. and J.D. All authors have read and agreed to the published version of the manuscript. Funding: This study was conducted under a research project funded by a statutory grant of the AGH University of Science and Technology in Krakow for maintaining research potential. Acknowledgments: We sincerely thank the anonymous reviewers and the editor for their careful- of our manuscript and their many insightful comments and suggestions. Conflicts of Interest: The authors declare no conflict of interest.

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