Mobile-assisted and gamification-based language learning: a systematic literature review

Learning a new language is a challenging task. In many countries, students are encouraged to learn an international language at school level. In particular, English is the most widely used international language and is being taught at the school level in many countries. The ubiquity and accessibility of smartphones combined with the recent developments in mobile application and gamification in teaching and training have paved the way for experimenting with language learning using mobile phones. This article presents a systematic literature review of the published research work in mobile-assisted language learning. To this end, more than 60 relevant primary studies which have been published in well-reputed venues have been selected for further analysis. The detailed analysis reveals that researchers developed many different simple and gamified mobile applications for learning languages based on various theories, frameworks, and advanced tools. Furthermore, the study also analyses how different applications have been evaluated and tested at different educational levels using different experimental settings while incorporating a variety of evaluation measures. Lastly, a taxonomy has been proposed for the research work in mobile-assisted language learning, which is followed by promising future research challenges in this domain.


INTRODUCTION
Mobile technology developments are quickly expanding the field of learning in non-formal education areas by rendering universal and instance-oriented access to privileged digital resources (Cheon et al., 2012). Mobile learning (m-learning) technology requires mobile devices to improve learning and academic performance by having the opportunity to learn remotely at all times in compliance with students' comforts. There have been many advantages to m-learning, including cost reductions, ubiquitous communication, research assistance, and location-based services. The goal of m-learning is to put the educational sector and associations at the center of academic progress to satisfy the users' demand for

LITERATURE REVIEW
Most of the surveys and systematically reviewed on MALL do not cover publication channels (Books or Scientific Journals), quality assessment, frameworks/model used, mobile and gamified applications used for teaching and learning, and comparison of these applications. Also, the focus was more on higher education students than on primary education. A more recent systematic review on the usage of mobile devices for language learning evaluated limited studies and from restricted repositories (Mahdi, 2018) (Cho et al., 2018). The author reviewed 20 studies for mobile devices' effect on students' achievement in which student's vocabulary learning results using handheld devices were compared to those using conventional learning (Cho et al., 2018).
In another study, the effects of embedded portable devices in learning and teaching were examined by reviewing 110 experimental and quasi-experimental journal papers published in 1993-2013. For the usage of mobile devices in school, a moderate mean efficiency was 0.523. Sung, Chang & Liu (2016) analyzed the impact size of moderators and the benefits and drawbacks of mobile learning, then synthesized based on the descriptive analysis from individual experiments at various levels of moderator variables. Another SLR of researches from 2007 to the present was on mobile education in K-12 in which ) reviewed a maximum of 63 articles from 15 journals, mostly exploratory and concentrated on the educational facilities associated with smartphone usage in learning. Furthermore, patterns and critical problems are also discussed for future research. Burston (2013) summarized 345 MALL research studies from 1994 to 2012, in a short overview of 80 words, to encourage researchers by presenting their historical background. The analysis included the home country, first or second or foreign language, the technologies employed for mobile apps, targeted research areas, type of students, demographic, study time, and the outcome summary. Finally, (Hwang & Tsai, 2011) targeted influential journals from 2001 to 2010 to investigate mobile and ubiquitous learning researches related to enhanced learning technology. The publications included Educational Technology & Society, Innovations in Education and Teaching International, Journal of Computer Assisted Learning, Computers and Education, Educational Technology Research & Development, and British Education Technology Journal. The researcher presented information for many journals, a selected search sample (primary school, secondary school, tertiary education, instructors and employees), study fields (language and arts, engineering, science, math, social sciences, and more), and countries involved. However, none focused on quality assessment, framework/models, grade or education level, adopted content, approaches, statistical analyses, and comparisons between MALL and gamified apps. In our review, both areas were thoroughly discussed and differentiated from the above studies then systematically chose methods and coded them with standard naming, according to strict guidelines.
This Systematic Literature Review (SLR) discusses MALL-learners in-depth, mobile, and game-based languages, and involves the five perspectives as in Table 1. Based on the structural analysis criteria, 67 research articles have been finalized and assessed in quantitative and qualitative terms for further analysis. The SLR's significance presents the new classification criteria, MALL research trends, developed/adopted research models, learning and teaching methods, learning content, comparisons of mobile and game-based apps, research methodologies, and approaches used to evaluate the studies. This SLR may allow instructors to build a standardized MALL environment with learning and teaching apps, learning materials, frameworks, and relevant methodologies.
The study of Sung, Chang & Liu (2016) chose experimental and quasi-experimental journal articles from the period 1993-2013 from ERIC and SSCI repositories (only eight journals were selected) to know the use of mobile experimental studies of teaching and learning achievement of students through these devices. The study Hwang & Tsai (2011) published in 2011, in which journal articles were selected from SSCI repository of the 2001-2010 period to know the status of mobile and ubiquitous learning, as well as research sample group along with learning domains related to technology, were adopted in selected articles. In the study of , the selected articles were taken from 2007 to 2012 for teaching and learning of K-12 education. The study aimed to know the effectiveness and trends of mobile devices in K-12 education, and the participants were younger than 18 years.
The study of Burston (2013) selected the studies from the period of 1994 to 2012 in the area of MALL and annotation in which only 80 words summary was provided consisted of country, native language, mobile technology used, learning area, type of learners, and numbers, and an overview of results. The study Mahdi (2018) examined the effect of vocabulary learning using mobile devices by selecting 16 studies from ERIC, IEEE Xplore, IGI, Sage, ScienceDirect and Springer. The study Cho et al. (2018) finalized 20 studies to see the effect of mobile devices in language learning on students' achievement, and ERIC, EBSCOhost, JSTOR and ProQuest repositories were filtered for the literature search. This systematic literature review aims to explore the Web of Science core collection for high-quality literature search to know the research trends of Mobile and Gamification based language learning. Moreover, a quality assessment of the selected articles was conducted along with the discussion of research frameworks/models and teaching and learning tools at all education levels.

RESEARCH METHODOLOGY
This survey implemented recommendations for systematic reviews given in information engineering analysis by (Brereton et al., 2007). Based on these criteria, a search method was defined to eliminate possible study biases after finalizing research queries. Within this procedure, three critical phases of our analysis approach were to prepare, conduct, and review the study, as shown in Fig. 1 and discussed in the following sections.

Review plan
An appropriate search strategy was created for all related studies. As shown in Figs. 1 and 2, the analysis methods indicate search procedures for the associated articles, describing the classification system and mapping of items. This study follows an organized approach: Finalizing the review report (i) RQ1 attempted to report our objective to develop an articles' library related to the MALL pupils and make the dataset accessible to other scholars. Furthermore, significant work was identified that provided direction to investigate students' issues in learning English. The answer to RQ1 discovered trends, geographical areas, and publication channels in the articles. (ii) To identify the theories and frameworks/conceptual models used for MALL research and relate them with one another and to different application areas for MALL. The solution of RQ2 provided the answer to this objective. (iii) RQ3 attempted to identify different target application areas of MALL from teaching and learning perspectives. Furthermore, other modes of exposition were identified for these MALL applications. (iv) How the researchers accommodated different MALL applications content focusing on reading, writing, speaking, and listening perspectives. For this purpose, RQ4 attempted to achieve this objective. (v) RQ5 attempted to outline the standard process, tools, and instruments used to evaluate MALL applications. Furthermore, MALL applications' evaluation measures were identified concerning different perspectives, including teaching and learning, and technical perspectives. (vi) RQ6 attempted to perform a comparative analysis to evaluate the effectiveness of simple mobile application-based language learning with gamified mobile applications for language learning. The research objectives and motivations of this research are transformed into relevant research questions (RQ), as shown in Table 2.

Review conduct
There were four steps in the review process formulated. In the first step, examination was made from web of science (WoS, 2020) with SCI-Expended, SCIE, ESCI and A&HCI indices consisting of high-impact research papers, for relevant primary studies. In the second step, the collection of studies was filtered based on predefined inclusion/exclusion criteria. We also established quality assessment standards to boost further the consistency in the third step of our analysis. Backward snowballing was then carried out in the final fourth step, to retrieve relevant candidate articles.

Automated search in web of science (WoS core collection)
A systematic investigation was made to filter irrelevant research and obtain adequate information. Our source was a curated database, Web of Science Core library that included over 21,100 peer-reviewed journals, top-class academic journals distributed worldwide (including Open Access journals), covering more than 250 disciplines (WoS, 2020). WoS is a tool that helps users collect, interpret, and share information from databases promptly (Princeton University, 2020). To conduct an SLR in an organized and timely manner, the researcher used this platform to retrieve the research articles by incorporating 'AND' and 'OR' Boolean operators with keywords to develop a search string. Figure 3 presented an overview of the search result obtained from the Web of Science. Table 3 lists the final search string incorporated 'AND' and 'OR' Boolean operators with keywords, used to explore WoS Core Collection. Only titles were searched from the The objectives of RQ1 were to search for high-quality research articles through major publications channels for MALL research. Furthermore, the quality assessment for the selected articles and the meta-information extracted useful statistics, including the geographical areas and publication, trended over the years.
RQ2: What were the widely used theories, models, and frameworks proposed or adopted for MALL research?
To identify the theories and frameworks/conceptual models used for MALL research and related them to different application areas for MALL.
RQ3: What were different application domains for the MALL application, and in which various forms were these applications exposed for the end-users?
To identify different target application areas of MALL from teaching and learning perspectives. Furthermore, identify different modes of exposition for these MALL applications.
RQ4: What was the specific content adopted for teaching and learning in MALL research? To perform a comparative analysis to evaluate the effectiveness of simple mobile application-based language learning with gamified mobile applications for language learning. database, and a filter of indices and period were applied to restrict the search query for the study.
Selection based on inclusion/exclusion criteria

Inclusion criteria
The paper comprised in the review must be in MALL, mobile learning, and m-learning that must target the research questions. Paper published in the journals or conferences also from 2010 to 2020 was included in the review. Papers discussing MALL at school, college, and university level, focusing on learning, teaching, learning, and teaching (both), games (Example: Serious Game, Mobile games, learning application) were also included in the review.

Exclusion criteria
The articles were excluded not written in English and did not discuss or focused MALL, mobile learning or m-learning in schools, colleges, and universities to teach and learn English. A selection process of relevant articles for inclusion/exclusion criteria in detail was shown in Fig. 4.

Selection based on quality assessment
The collection of appropriate studies based on quality assessment (QA) was considered the critical step for carrying out any review. As the fundamental studies differed in nature, the essential assessment tool (Fernandez, Insfran & Abrahão, 2011) and (Ouhbi et al., 2015) used to conduct QA were also supplemented in our analysis by quantitative, qualitative, and mixed approaches. The accuracy of the selected records was determined using a QA questionnaire. The first author conducted the QA, using the following parameters for each study: (a) If the analysis led to MALL, mobile language learning, m-learning, the result was indeed (1), otherwise (0).
(b) When there were simple answers for the MALL, mobile learning, m-learning of English, the analysis provided the following scores: 'Yes (2),' 'Limited (1) ' and 'No (0).' (c) If the studies provided an empirical result, then award (1) else score (0). (d) Studies analyzed concerning graded rankings of countries and journals (SCImago Journal & Country Rank (SJR), 2018) and conferences in computer science (CORE

2010-2020
Conference Portal, 2018). Table 4 indicated potential findings for publications from known and reliable sources. After combining the scores to the above questions, a final score (between 0 and 8) was determined for each study. Only papers included with four or more ratings in the final results.

Selection based on snowballing
Following the standard assessment, backward snowballing was performed, employing a reference list from any completed analysis to retrieve papers (Mehmood et al., 2020) and chose only those significant articles that met inclusion/exclusion requirements. After reading the introduction and then other portions of the document, the article's inclusion/ exclusion was determined.

Review report
This section provided an overview of the selected studies.

Overview of intermediate selection process outcome
MALL was a very active topic, and our analysis approach had to extract relevant research empirically and systematically from the Web of Science core collection. The next step of our systematic analysis was compiling records that form the foundation for this analysis. Approximately 57,000 papers were examined from the archive by providing the keywords for 2010-2020. After creating a knowledge base from the digital library (Web of Science), the author reviewed the title, abstract, and accompanying complete document for each search result, as needed. During this process, irrelevant papers or papers of less than four pages were eliminated. During the inspection process, selected documents in the fields of MALL, mobile learning, and m-learning were read extensively to assess their significance & contribution and then created a comprehensive knowledge foundation of papers based on their findings to accomplish this research's core objective.
Overview of selected studies Table 5 presented significant results of the primary search, filtering, and reviewed processes that included Web of Science indices. At the filtering/inspection stage, this amount decreased to 63 articles by the automatic search.

ASSESSMENT AND DISCUSSION OF RESEARCH QUESTIONS
In this section, finalized 67 primary research studies based on our research questions were scrutinized.

RQ1
: What are the high-quality publication channels for MALL research, and which geographical areas have been targeting MALL research over the years?
The analysis of MALL with the integration of game elements in learning tools, methods, content, and the theoretical perspective choice was a crucial challenge for scholars to use in education. Identifying fine publication sites and scientometric analysis based on meta-information in MALL domain was required for the purpose. This section consisted of perceptive knowledge of research publication sources, types, years, grade level distribution, geographical distribution, publication channel-wise distribution of selected studies to analyze MALL research.
The studies finalized from the Web of Science (core collection) were presented yearly, as shown in Table 6 and Fig. 5. Twelve was the maximum number of publications selected from the year 2019, out of the total 67, indicated more interest in developing MALL with integrating games in teaching and learning. However, less interest in MALL with game research integration was observed in 2010-2016 and 2018-2020, resulting in less improvement in teaching and learning in relevance to students and market needs.   Table 7 and Fig. 6 present the geographically distributed studies. The majority of publications, or 39 out of 67, were from different Asian countries, whereas European countries published 15 reviews. North American countries published eight studies, while Africa and Ocean-continent have three and two studies published, respectively.
The data presented in Table 8 showing that the maximum number of articles were from highly recognized journals indexed in the Web of Science. Only one item was from a good ranked conference. Computer & Education journal was on the top of the list from which seven papers were selected and next, the Educational Technology & Society journal with four articles.
According to conditions defined in "Research Methodology" B.3, each finalized study's QA score was granted, as shown in Table 4, offering the QA score ranging from 4-8,  with less than four discarded scores. MALL researcher might find this QA supportive to choose related studies while addressing its usage and challenges. Articles published in Q1 journals mostly scored maximum while scoring four from less recognized journals but relevant to the subject matter. A total of 26 out of 67 scored maximum (i.e., eight (8), indicating fulfillment of all QA criteria, whereas nine (9) studies scored four out of 67, which is the lowest in QA). Table 9 presented the overall classification output and QA of finalized studies, and Table 10 showed the overall quality assessment score. Studies were classified based on five factors: the empirical type/method, research type, and method. Categories of research types were; Evaluation framework, Evaluation research, Solution proposal, and Review. The taxonomy presented in section V was constructed on these defined research types.
Studies that analytically validated their results from the statistical analysis, experimentations, surveys, or case studies to increase their quality standards awarded a score. In category (c) of quality assessment criteria, only 8 out of 67 reviews did not present empirical results, thus awarded zero scores. Only five studies scored zero for category (d) of quality assessment criteria; the rest of them scored higher, indicating competent sources. Four (4) recorded the lowest score awarded for a study.
RQ2. What are the widely used theories, models, and frameworks proposed or adopted for MALL research?
This section provided the framework/conceptual model based on the situation (proposed/adopted by the researcher) after an essential discussion of the theories, frameworks, and models.

THEORIES
Theory of planned behavior: The Theory of planned behavior (TPB) noted that behavioral intentions motivated human behavior. Behavioral intentions rely on three determinants; an individual's mood, cultural norms, and perceived influence (Cheon et al., 2012). Sociocultural theory: Sociocultural theory recognized human evolution as socially influenced by cooperation with more professional members of society, through which children learned their cultural norms, ideologies, and problem-solving techniques (Kearney et al., 2012) (Mcleod, 2020). Experiential Learning Theory: The concept of experiential learning was implemented in a learning game. Players performed exercises to seek information within a gameplay environment that made the learning process enjoyable, engaging, and interesting (Tsai et al., 2016).
Dual-Coding theory: The dual-coding theory suggested that the verbal and imagery systems (mental images and representations) could be co-activated as rich and substantive referential relations connected dual-coded objects (Teng, 2018).   Theory of cognitive style: Two types of learning, field independence and field dependence, were based on critical and interpersonal personality characteristics. Fieldindependent students were independent-minded, and the social environment could not readily affect their learning style. Field-dependent students tended to learn in visual settings or scenarios (Ou-Yang & Wu, 2016).
Attribution theory: Bouchaib (Bouchaib, Ahmadou & Abdelkader, 2018) used Weiner attribution theory (1992) as a framework that provided failure or success reasons or explanations for people in education. Moreover, it was also a social cognitive theory of motivation.
Instructional theory: The instructional theory sought to explain how people can learn, evolve, and established environments that promote learning opportunities and strengthen teaching (Fisser, Voogt & Bom, 2012) (Top Hat, 2019).
Frameworks & models 'Here and now' mobile learning framework: Three characteristics (Engaging, Authentic, and Informal) Framework identified the effect of mobile learning on the learning environment (Martin & Ertzberger, 2013).
Mobile English learning outcome (MELO) framework: This research developed the Mobile English Learning Objective (MELO) to examine the correlation between learners' understanding of mobile technologies using playfulness, resistance to change, and selfmanagement constructs of the Framework (Huang et al., 2011).
M-COPE: It is a study that came up with the M-COPE framework to support teachers in building mobile learning experiences using the ADDIE model, which allowed teachers to understand five main aspects of mobile learning: Mobile affordance, Ethics, Pedagogy, and Outcomes (Dennen & Hao, 2014).
Mobile English learning continuance intention (MELCI): The study came up with TAM components (Davis, 1989) adopted in mobile English learning. Continuance intention framework to examine the influence of mobile learning satisfaction with self-management of learning (Huang, 2014). Pedagogical Framework: Task-based language teaching (TBLT) was a pedagogical framework concerning language instruction strategy that focused on curricular design units and an instructional cycle aspect. It focused on the interaction method, which implied that the negotiation of importance led to a detailed and internationally changed input (Chen & Lin, 2018).
The affordance framework: The affordance framework, which comprised pedagogical, social, and technological components, examined the ICT tools affordance for language learning (Ramadoss & Wang, 2012).
Technology Acceptance Model (TAM): The TAM demonstrated many knowledge predictors by many researchers, focusing on the rational action theory. TAM has five components: perceived ease of usage, perceived effectiveness, the intention of behavior, intention to use, and discrete use. The model played an essential role in forecasting the use of various factors .
Extended Technology Acceptance Model: The study examined mobile applications' impact on students' usage intention, perceived ease of use (PEOU), and usefulness. The research outcome was an extended technology acceptance model (Bohm & Constantine, 2016).
ARCS Model: A motivational model ARCS (Attention, Relevance, Confidence, and Satisfaction) that motivated learners and procedural assistance in compliance to demand used in this research. This model has three features: (1) emphasized motivation and emotional stimulation, (2) integrated with other theories and design, (3) enhanced the instruction effects and learning process (Wu, 2018).
A Theoretical Model: Discussion of two frameworks: (1) Framework for the rational analysis of mobile education (FRAME). (2) TAM and TAM 2, the author proposed a new theoretical model that focused on the technology enhancement, non-formal learning setting, and learner-centered to develop a better understanding for EFL learners using mobile English learning resources (MELR) for Chinese postgraduate students .
In this section, the Theory, Framework, and Model used in the studies were described and summarized in Table 11.
A conceptual model based on the Theory of Planned Behavior (TPB) explained how young adults' acceptance and attitude affect their intention to embrace mobile devices in their classroom practice (Cheon et al., 2012). The Framework in (Kearney et al., 2012) criticized pedagogy, allowed a comparison of mobile approaches and pedagogical methods, and their importance to the sociocultural nature of learning in mobile learning environments validated by m-learning researchers' discussion among designers of the Framework, implementation in a project, and pedagogical experts. Similarly, three characteristics (Engaging, Authentic, and Informal) Framework were created to see mobile learning's effect on the learning environment by measuring students' achievement and attitude (Martin & Ertzberger, 2013). A hypothesized m-learning model was proposed based on the Technology Acceptance Model (TAM) components-Perceived Usefulness  2019 English language learning Not Available Self-regulated learning framework by Garrison Self-directed learning, Garrison's comprehensive theoretical approach (1997) was used in this research. (Yurdagül & Öz, 2018) 2018 English language learning Not Available Not Available The study investigated the higher education students' attitude towards using the smartphone for language learning.
(Continued )  change, and Self-management that were adapted after discussing extensive literature (Huang et al., 2011). The M-COPE framework supported teachers to build mobile learning experiences using the ADDIE model. This Framework allowed teachers to understand five main aspects of mobile learning: mobile affordance, Ethics, Pedagogy, and Outcomes. It was validated by five experts (Dennen & Hao, 2014). The computational model concept and their proposed connections resulting from Davis (1989) TAM were introduced in which perceived ease of use, perceived usefulness, and perceived contextual variables were measured. This model was validated through SmartPLS 2.0 (Bohm & Constantine, 2016). A motivational model, ARCS (Attention, Relevance, Confidence, and Satisfaction) that considered learners' motivation and procedural assistance in compliance to demand, was used to measure effectiveness and learning motivation. This model has three features: (1) emphasize motivation and emotion stimulation, (2) integrated with other theories and design, and (3) enhances the instruction effects and learning process (Wu, 2018). A mobile English learning continuance intention framework was used. TAM (Davis, 1989) was adopted to see the influence of mobile learning English satisfaction with self-management of learning to measure Perceived Usefulness, Perceived Playfulness, and Resistance to change. The internal consistency and reliability were measured through the PLS-SEM application (Huang, 2014).
The study adopted the TAM by incorporating perceived convenience and curiosity factor for mobile learning. To examine the validity of the measurement model, Confirmatory Factor Analysis (CFA) was performed with SmartPLS . In contrast, experiential learning theory was used because players seek knowledge by doing activities in the game environment. Moreover, the learning process was exciting, challenging, and relevant, along with substantial experience provided to the players where learner motivation and effectiveness were measured (Tsai et al., 2016). In a dual-coding theory, the working memory model and multimedia principle used for pedagogy in this study were validated by doing an extensive literature review (Teng, 2018). In this research, self-directed learning, Garrison's comprehensive theoretical approach of (1997), was used to measure self-directed learning (motivation, self-management, and selfmonitoring) (Botero, Questier & Zhu, 2018) whereas 'English Fun Dubbing' application was designed for practicing English orally, and evaluation of the application's effectiveness (convenience, flexibility, user-friendliness, rich material, language context) was carried out by Zhang (2016). An application was developed to observe the multimedia glosses' effect on second language listening comprehension and vocabulary learning in a mobile learning environment. Its effectiveness was measured by the author (Çakmak & Erçetin, 2017).
Business language testing service (BULATS) adopted a framework based on Teaching Method, Learning Satisfaction, Learning Effectiveness, and qualitative analysis to measure satisfaction and attitude (Shih, 2017). 'MyEVA Mobile' is a mobile-based application developed to explore the learning attitude, learning achievements, learning styles, and university students' strategies to improve the students' vocabulary that worked any time and without the internet. The framework components are 'Smartphone client,' 'Wireless device,' and 'Log Analyzer Server.' Learning behavior, Perpetual learning styles, and Knowledge proficiency were measured in this study (Ou-Yang & Wu, 2016). In another study (Chen & Lin, 2018), task-based language teaching (TBLT) was used as a pedagogical framework to measure technology-mediated TBLT. 'Weiner attribution theory (1992) was used as a framework that provided failure or success reasons or explanations for people in education (Bouchaib, Ahmadou & Abdelkader, 2018). Moreover, WhatsApp and Google were used to enhance the reading ability to measure learner autonomy (Hazaea & Alzubi, 2018) and retain business vocabulary, whereby an application 'Excel@EnglishPolyU' was developed and tested with undergraduate students (Kohnke, Zhang & Zou, 2019). To design and implement a mobile-based English vocabulary application for distance learning students in South Africa, 'VocUp' was developed, and its evaluation measures usability, scalability, reliability, and flexibility (Makoe & Shandu, 2018).
A theoretical framework for 'Word Score' serious game was developed based on Bom (2011) by exploring the literature to measure this study's motivation (Fisser, Voogt & Bom, 2012). In contrast, an architectural model was proposed in the study. The Pedagogical model, and learner model, were used by pilot testing (Bourekkache & Kazar, 2020), whereas a mobile game for tenses' SOS Table' was developed. The evaluation measured its effectiveness, user's motivation, acceptance, and attitude within the Framework of mobile learning tools (Önal, Çevik & Şenol, 2019). Moreover, by discussing two frameworks: (1) Framework for a rational analysis of mobile education (FRAME) and (2) TAM and TAM 2, the author proposed a new theoretical model that focuses on the technology enhancement, non-formal learning setting, and learner-centered to develop a better understanding for EFL learners on mobile English learning resources (MELR) in English language learning for Chinese postgraduate students . Furthermore, it was also a social cognitive theory of motivation. Simultaneously, the affordance framework consisted of pedagogical, social, and technological components, used to examine the ICT tools affordance for language learning (Ramadoss & Wang, 2012). TAM was used in the study to measure perceived usefulness and ease of use .
Several tools have been designed and developed by the researchers in MALL to support the students and teachers in learning the English language. A more in-depth analysis presenting that most of these tools and applications are student-centric and focus on learning . While some of them support teachers in teaching and students in learning, thus can be categorized as a teaching and learning tool . On the other hand, very few tools focus only on teaching (Ramadoss & Wang, 2012). Lastly, another emerging trend has been observed where these tools are augmented with gamification to make them more exciting and useful for the stakeholders (Chu, Wang & Wang, 2019). Table 12 presents these tools in different categories above.

Learning aspect
A mobile adaptive language learning system in which recommended material for reading and reading annotation facilities was provided to pupils to improve learning outcomes (Hsu, Hwang & Chang, 2013). A Mobile learning tool and five-step vocabulary learning (FSVL) strategy were developed in a situational learning environment to assess their effects on English as a foreign language (EFL) performance and learning motivation. According to the mobile learning tool, a global positioning system (GPS) was used to develop and provide learning material (Huang et al., 2016). Similarly, a mobile learning application 'Raz-Kids' for an extensive reading program was designed by 'Learning A to Z.' The tool aimed to create the concentration of the students to enhance their essential reading ability. Furthermore, it provides e-books of alphabets for students and teachers' class management tools (Lin, 2014).
The study conducted experimental research using ASR, Non-ASR and Control Group. The ASR group Nuance Dragon Dictation application was designed and installed on their mobile phone to finish weekly pronunciation activities with immediately written visuals (Pictures) feedback provided by the application without any human interaction. Five native French speakers pronounced all words and phrases to test the application (Liakin, Cardoso & Liakina, 2014). In a study by Chang et al. (2013), 'Mebook,' a multimedia eBook system that can be played in the format of MP3 was developed. It integrated text, images, voice, and pictures that provided directions for listening, speaking, writing, and reading.
Furthermore, it also included speed adjustment of audio and switching of language from English to Chinese and Chinese to English. Duolingo, a free mobile assisted language learning tool (for vocabulary acquisition) is available in the web and mobile (Android and iOS) versions to examine out of class engagement informally. Translation exercises of sentences and words are the delivery method of this application. Moreover, instructors can see logs and progress to keep an eye on the students (Gafni, Achituv & Rahmani, 2017). A mobile-based gaming approach for English grammar and vocabulary learning 'Save the princess with Teddy' was developed and students' learning achievement with gameplay at different levels was analyzed. It was hoped to enhance students' learning motivation with the game and assistance to learn the English grammar concept (Chu, Wang & Wang,

Not Available
The data is taken from the application& manually is considered one unit.  To investigate a mobile English learning application that would be supplement and support for learning English at school was adopted for the study by enhancing game features.

Adapted from Literature
An online database to store data (Wu, 2018) 2018 English Vocabulary Practice System Game The mobile-based English Vocabulary system for practice was designed and developed to provide students with assistance to review, proficiency, and practice in the class and after the class.

2019).
In the context of academic English, a mobile data-driven learning (DDL) experiment was discussed by designing and developing an application' AKWIC (academic key words in context)' for voluntary. This application provided support for academic writing (vocabulary learning), and data were obtained from logs generated by the application (Quan, 2016).
An SMS text message application, 'Fetion' explores the effectiveness of vocabulary learning using mobile technology. Specifically, SMS from mobile phones enhanced English vocabulary than outdated printed material (Zhang, Song & Burston, 2011). In contrast, a location-based vocabulary learning activities application for Thai and German users was proposed in a study with personalized learning motivation. Moreover, the aim was to enhance user acceptance by providing relevant learning content to evaluate an online questionnaire (Bohm & Constantine, 2016). A free mobile assisted language learning tool (vocabulary acquisition) 'Duolingo,' available for web and mobile (Android and iOS) versions examined out of class engagement informally. Translation exercises of sentences and words are the content of this application, and instructors can see logs and progress to track students' progress (Botero, Questier & Zhu, 2018). 'Mobile assisted listening application' was developed to examine L2 multimedia glosses' effects in a mobile learning environment, for vocabulary and listening comprehension, validated through a pilot study (Çakmak & Erçetin, 2017).
An offline mobile assisted language learning application system, 'My English Vocabulary Assistant mobile edition' (MYEVA Mobile) was developed to engage students in mixed-modality vocabulary learning to improve their vocabulary. The users learned targeted words via four vocabulary learning strategies: flashcard, imagery, word card, and Chinese assonance. A log analyzer server was installed, and log files were used to analyze the results (Ou-Yang & Wu, 2016). Furthermore, a mobile application like WhatsApp and Internet search engine (Google) were used by students to access materials for reading Not Available Log File from the DB server in which usage behavior is recorded. (Fisser, Voogt & Bom, 2012) 2013 Word Score A serious online game was designed to extend the students' vocabulary in primary school was discussed in this study.
This game was part of the national project 'Educational Time Extension (ETE)'.
Not Available Not Available and interaction with peers and instructors outside the class. This application was used to improve learning skills in EFL reading (Hazaea & Alzubi, 2018). A crowdsourced mobile-based 'LingoBee,' an open-source and freely available application, explored creativity and mobility in language learning. It was the part of the European countries' project "SIMOLA", designed to help collaborative language learning using the idea from social networks and crowdsourcing. Users created content for language learning, stored it on their device, and shared it with other users via a cloud-based repository. The application was evaluated through user studies in European countries (Petersen, Procter-Legg & Cacchione, 2013). In contrast, an application 'English Practice' was used to analyze the usage behavior of 53,825 users from 12 countries, and the evaluation was conducted through log files generated by the Google Firebase analytics tool (Pham, Nguyen & Chen, 2017).

Teaching and learning
An online assessment tool, 'Grammar Grabber,' was discussed in this study to evaluate grammar at the school level. Using this tool, users do practice online and get constant feedback to know their performance. The authors investigated this online assessment tool to perceive pedagogical, technological, and social affordances using multiple-choice questions and allowing re-attempt for wrongly answered questions. The log files of the application were used as the dataset (Ramadoss & Wang, 2012). An application, 'Literacy and Numeracy Drive' to teach and learn languages, was discussed at the school level. This application provided some practice and then some assessment exercises for the English language. This application aimed to teach singular/plural, use of has/have/had/is/am/are/ was/were, and reading comprehension . A serious online game that was designed to extend the students' vocabulary in primary school was discussed in this study. This game was part of the national project 'Educational Time Extension (ETE).' The students spend more time than expected class timing to learn and improve their vocabulary. Applications for teaching and learning at the college level was not adopted/ developed for English language learning in the selected studies.
LINE App, an application that was used to investigate the teaching of English for specific purpose (ESP) effects on Business Language Testing Service (BULATS) (Shih, 2017). Whereas 'Mobagogy' a professional learning community of academicians to investigate the use of mobile technologies in learning and teaching while 'The bird in the Hand' initiative by the UK to examine the experience of trainee and newly qualified teachers by providing them smartphones to use in their offices and teaching schools to enhance professional practices of pedagogy. Australian University developed the application Mobagogy', and The Bird in the Hand was sponsored by the UK (Kearney et al., 2012) to evaluate the benefits of mobile applications and an application 'English Fun Dubbing' designed for English's oral practice its users. Learning material in this application was: animations, songs, movies, short videos, and textbooks developed by the Chinese Sci-Tech Company (Zhang, 2016). To enhance teaching and learning of English vocabulary, a mobile-based application 'VocUp' was designed and implemented to evaluate external parties (Makoe & Shandu, 2018). A mobile application, 'WhatsApp' was used in this study to examine the efficiency of teaching 40 phrases.
Furthermore, the study also aimed to enhance vocabulary acquisition (Shahbaz & Khan, 2017). An application 'Anglictina (English) TODAY' was developed by a Ph.D. student of Computer Science with a language teacher's help. This application helped pupils for the preparation of final exams by learning from anywhere at any time. To discuss students' perception of using a mobile application, this was developed based on their needs to make EFL vocabulary teaching and learning useful (Klimova & Polakova, 2020).

Gamification based learning and teaching
A serious game 'MEL application' developed in which 25 animals from five continents (Asia, South-America, Africa, Oceania, and North-America) were involved developed. The game was played during the visit to the zoo and at home in which two modes were available in which one was totally related to the zoo situation. One was independent of GPS that allowed children to access animals in different continents (Sandberg, Maris & Geus, 2011). To investigate a mobile English learning application that would be supplement and support for learning English at school was adopted for the study by enhancing game features. The application's learning material on animals from the zoo resulted in the students' outperformance using the mobile application for a fortnight than users for a fixed period (Sandberg, Maris & Hoogendoorn, 2014). A game-based system, 'Happy English Learning System,' in which learning material was integrated to experiment, was installed on mobile devices to see the learner's motivation for achievement. The activities were divided into levels of difficulties: Easy, Medium, and Advanced, according to the ability of users (Tsai et al., 2016).
Game-based applications Excel@ EnglishPolyU, Alphabet vs. Aliens, and Books vs. Brains@PolyU, business vocabulary after completing level challenges may acquire by the learners (Kohnke, Zhang & Zou, 2019). Similarly, an application, 'PHONE Words,' was developed by Alice English Education Studio for vocabulary learning, designed with game functions (MEVLA-GF) and without game functions (MEVLA-NGF) to investigate the perceptions and measure the learning performance of learners. This application also provides an assessment with a gamified competition mechanism (Chen, Liu & Huang, 2019). To give the students' opportunity, 'SOS Table,' a mobile-based game application, was designed and developed to repeat tenses, high-frequency words, and sentence string. Time challenge was provided to create negative, positive, or correct sentences with words and pronunciation after completing the task (Önal, Çevik & Şenol, 2019). The serious game was not adopted/developed at the college level for English language learning in the selected studies.
In the study (Holden & Sykes, 2011), an augmented reality-based language learning game developed for Spanish in Southwestern US to explore foreign and second language learning's benefits and complexities. Similarly, a mobile-based English Vocabulary system for practice was designed and developed not to replace traditional classroom teaching methods. The aim was to provide students with assistance to review, proficiency, and practice in and after the class. The game system was designed based on the ARCS model, which provided assistance in vocabulary learning and listening and worked as a testing tool (Wu, 2018). 'Idiomobile' a mobile-based game that was made available for specific handsets based on the knowledge of using idiomatic expressions in a critical situation (Amer, 2014).
RQ 4. What is the specific content adopted for teaching and learning in MALL research?
Teaching and learning through MALL by applying pedagogical skills or tools after adopting appropriate content are summarized and discussed in this section. The current section is divided into four sub-levels, i.e., Learning, Teaching and Learning, and Serious Game based presented in Table 13.
The content usage for learning aspect in MALL about reading perspective discussed for the undergraduate students of public university enrolled in "Computing and Information Technology (CIT)" adopted as curriculum (Cheon et al., 2012). Whilst personalized recommended learning material with reading annotation services were categorized into three difficulty levels: elementary, intermediated, and intermediated high level (Hsu, Hwang & Chang, 2013). In the study (Bohm & Constantine, 2016), discussed that multimedia learning material in the written and audio-visual form provided using the app according to the user's relevant current position. Words and pictures were adequate for learners to learn vocabulary by solving word pair quizzes. The content adopted in  was broad and varied, including current issues related to education, economy, environment, social, politics, technology, etc. For English learning, the topic areas covered were speaking, listening, reading, and vocabulary. To teach most popular idioms, content relevant to idioms and collocations was collected for application from books and websites (Amer, 2014).
A cooperative creation of multimedia content by adding it to new vocabulary is then stored on the devices and uploaded on the cloud by the users that can view or brows LingoBee repository by sorting it chronologically or alphabetically (Petersen, Procter-Legg & Cacchione, 2013). The study (Tsai et al., 2016) discussed the curriculum for English subject consisted of the topics: phonetic symbols, alphabet, grammar, phrases, vocabulary, and sentence patterns used by pupils to review it and also can share with the class by using social media (i.e., Facebook) whereas the course content in application 'Duolingo' focused variety of subject-specific vocabulary acquisition by learning nearly 2,000 words. The application's delivery techniques were translating from source to users' target language, choosing right translated phrases, paring of words from languages, flashcard practicing, and translation of unknown words (Botero, Questier & Zhu, 2018).
Teaching is a method of discussing and interfering with people's desires, perspectives, and emotions to learn specific things (P. byinfed.org, 2020). The reading perspective in teaching is discussed by Ou-Yang & Wu (2016) in which the content used for vocabulary teaching, suitable for 'Test of English for International Communication (TOEIC) that is a standardized test used in Taiwan. Fifty words were taken for vocabulary was chosen from TOEIC, including different difficulty levels. The participants were undergraduate students at a large, public university in which students were enrolled in a subject, "Computing and Information Technology (CIT)" which was the core curriculum subject required by all the students.
Reading annotation 2013 (School) (Hsu, Hwang & Chang, 2013) Quasi-Experiment with the Technology Acceptance Model and Cognitive Load questionnaire Personalized recommended learning materials with reading annotation services were provided to the students by analyzing profiles and portfolios using a developed adaptive learning system. Conceptual Paper A language learning application 'LingoBee' was designed for the cooperative creation of multimedia content by adding it to new vocabulary by the users. It was stored on the device of the users then uploaded to the cloud provided by the application. The content could be viewed or browsed LingoBee repository by sorting it chronologically or alphabetically.
Phonics, Symbols, Vocabulary, and Sentence pattern 2017 (School) (Tsai et al., 2016) Quasi-experimental method The English subject's curriculum consisted of phonetic symbols, alphabet, grammar, phrases, vocabulary, and sentence patterns. Pupils could use the HELS application to review the content and share the content prepared by them in the class and social media (i.e., Facebook).
Vocabulary acquisition 2019 (University) (Botero, Questier & Zhu, 2018) Dashboard, Questionnaire, and Interview The course content in application 'Duolingo' focused on various subjects, specifically vocabulary acquisition, by learning nearly 2000 words. The application's delivery techniques were translation from source to target language of users, choosing the right translated phrases, paring of words from languages, flashcard practicing, and translation of unknown words.
Current studies investigated the content usage according to speaking, listening, reading, and writing in teaching and learning through MALL. An application designed by the Chinese Sci-Tech company to assist in English practice orally provided rich learning material of animation movies, short videos, songs, and textbooks with English speakers

Interviews
To learn Spanish from an augmented reality (AR) gamebased language learning tool, gameplay, narrative, setting, and curriculum were added. The classroom curriculum was adopted for the game for the three-tofour-week timeframe.
Vocabulary practicing 2018 (University) (Wu, 2018) Questionnaire A game-based English vocabulary practice system in which the vocabulary presentation model combined learning content with difficult vocabulary levels.
Vocabulary learning 2019 (University) (Chen, Liu & Huang, 2019) Questionnaire and Interviews For vocabulary learning using MEVLA-GF, interviewees' perception identified gamified design, interface design, and content design. The interface and gamified design efficiently be used, and content should also satisfy the learners' needs for different purposes and at the level for vocabulary learning. speaking for different age group students (Zhang, 2016). From the reading perspective, 'Word Capsules (short vocabulary test)' was developed in which words (content) were selected from 10,000 words, who gripped numerous phrases in English have a vast vocabulary and able to survive with challenges of studying at a higher level in English (Makoe & Shandu, 2018). In contrast, for all the viewpoints, practicing and retaining new phrases and words, ten lessons of vocabulary and ten lessons of phrases were adopted as content that the pupils have to translate to English from native language (Klimova & Polakova, 2020). The content used in game-based applications for reading perspective investigated from selected studies in which the content was pictures and videos to learn about the zoo animals (Sandberg, Maris & Geus, 2011). Learning Spanish Augmented reality game-based language learning tool was also investigated in which classroom curriculum was adopted for the game for three to four-week timeframe (Holden & Sykes, 2011). For vocabulary practice through a game-based system, a presentation model combined learning content with difficulty levels (easy, medium, and advance) (Wu, 2018). Still, for vocabulary learning using MEVLA-GF, the perception of interviewees identified gamified design, interface design, and content design that satisfy the learners' need for different purposes and at level (Chen, Liu & Huang, 2019). In the study of Chu, Wang & Wang (2019), learning material consisted of vocabulary, sentence examples, grammar examples, and grammar concept mapping for English games in elementary school. The purpose was to make a strong foundation of English grammar and enhance its knowledge with the understandability of relationships between concepts.  Table 14 shows that 33 out of 67 studies adopted or developed a questionnaire to collect data from the selected population. In contrast, only six studies used interviews and observations for their studies. The mixedmethod approach in which questionnaires, interviews, and observations were used as a tool for collecting data by 18 studies while only five studies used discussion and other methods for their data collection.

Evaluation
The evaluation in this section was teaching and learning and technical perspective. Researchers used various methods to collect data, and statistical tests were applied to analyze the data to produce relevant results. The statistical tests for analysis applied through various tools were, i.e., SPSS, PLS, etc. The methodology and tools used by the selected studies were presented in the following section.

Measures for teaching and learning
In the teaching and learning section, terminologies were described from the selected studies also presented the instruments used in these studies were shown in Table 15.
Pedagogy: a study of educational techniques, including the purposes of instruction and the approaches to accomplish them (Peel, 2017).
Motivation: originates from the term 'motive' that means needs, wants, wishes, or drives in people. It is the method of inspiring individuals to take steps to meet the targets (MSG Management Study Guide, 2020).
Perception: To organize, define, and interpret sensory input to reflect and recognize the input or situation presented (Perception, 2020).
Curiosity: originated from the flow concept, which means people prefer to communicate in the state of flow with their surroundings. Curiosity is preserved when people consider the world as fun or fascinating .
Continuance Intention: The level to which people intend to keep using smartphone English learning .
Attitude: An optimistic, pessimistic, or mixed assessment of an entity communicated at a certain level of anxiety. This represents an advantageous or disadvantageous assessment of a person, position, object, or event (iEduNote.com, 2020).
Achievement: Somebody succeeded in achieving something, particularly after much effort (Collins English Dictionary, 2020).
Self-Directed Learning: A learning approach that encourages learners to take control of their learning method (diagnosis requirements for learning, assessment of learning priorities, choice of learning methods, and the measurement of academic achievement and outcomes) (IGI Global, 2020). Behavior Pattern: A repeated way for a person or group to behave against a particular object or condition (Dictionary.com, 2020).
Learning Behavior: Learning Behavior stresses the crucial relationship between child and youth learning and their social experience and behavior (Northampton Centre for Learning Behaviour, 2020).
Learner Autonomy: The autonomy of learning is when pupils take care of their learning, both in respect of what they learn and, in the direction, they study it (Oxford University Press ELT, 2013).   Affordance: An affordance is an object quality or a condition that makes it possible for the person to take action (Definitions for Affordance, 2020).

Technical evaluation measures
It is the Human-Computer Interaction (HCI) category to measure the applications' UI/UX . The following were the terminologies discussed in selected studies also, approaches used in these studies were shown in Tables 14 and 15.
Usefulness: The perceived usefulness (PU) is also one of the separate structures in the TAM. It is the extent to which a person believes that a specific process may improve the efficiency of his/her job (World Leaders in Research-Based User Experience, 2020) (Ishaq et al., 2020c).
Ease of Use: The primary use of computer programs in the TAM is a significant determinant of the target. A discreet individual describes a simple usage as evident in implementing a procedure and directly impacts the perceived usefulness .
Effectiveness: Effectiveness is a participant's ability to execute a task in a given context. In general, efficacy is assessed by determining whether participants can carry out such tasks (Harrison, Flood & Duce, 2013).
Perceived convenience: The extent to which users perceive mobile English learning to be comfortable in terms of time, location, and the method to complete a task .
Usability: Usability is a common factor that determines how convenient it is to use interface design. The term "usability" also applies to the approaches used during the design process to increase ease of use (World Leaders in Research-Based User Experience, 2020).
Efficiency: Efficiency is the user's ability to deliver their role quickly and productively, representing the user's value during its use. Quality can be calculated in various ways, for example, the time taken to complete or the number of keystrokes necessary to finish a task (Collins English Dictionary, 2020).
Scalability: Scalability is characteristic of an entity, structure, model, or process, defining its ability, under increased or expanding workload or scope to handle and compete well (Hayes, 2020).
Reliability: Reliability means the possibility that a product, device, or service can perform its intended function properly for a given period or work without interruption within a fixed environment (ASQ, 2020).
Flexibility: Flexibility is a characteristic that explains how a person can tolerate changes in situations and think in novel, imaginative ways about issues and tasks (Flexibility, 2020).

Tools used for analysis
Nvivo is a tool that was qualitatively used by Wang, Zou & Xing (2014) and Quan (2016). After conducting interviews of their respondents, while only two (02) studies (Klimova & Polakova, 2020) (Ramadoss & Wang, 2012) evaluated their results manually to present in the articles. Mplus is a statistical modeling program that allows researchers to analyze the data used by Cheon et al. (2012), whereas 'Wenjuan Wang' an online tool to analyze data used in China by Zhang (2016). 'Facets,' 'Google Firebase,' 'Notes taking,' online tool, and 'Google Sheet' used by Uematsu (2012)  Mobile and gamified language learning applications from the selected studies concerning level, purpose, evaluation method, and results are presented in Table 17. The applications are divided into two categories: (1) Mobile application, (2) Gamified applications (serious games). Mobile applications are proposed for teaching (Kearney et al., 2012) (Zhang, 2016), reading (Hsu, Hwang & Chang, 2013)   Did not use analysis tool 11    (Liakin, Cardoso & Liakina, 2014), writing, reading, listening and speaking , listening comprehension (Çakmak & Erçetin, 2017), grammar (Chu, Wang & Wang, 2019) and reading comprehension . The results presented by studies for the applications of pedagogy, reading, pronunciation, writing, listening, speaking, grammar outperformed the control group. It may be concluded that mobile applications for vocabulary learning have a positive impact on language learning in which pupils from the experimental group outperformed the control group except (Klimova & Polakova, 2020)  where the students and teachers mentioned they are not satisfied with the design, content, assessment methods adopted in the applications besides pronunciation support and teachers' notifications were also missing. Gamified applications are proposed for vocabulary learning (Sandberg, Maris & Geus, 2011) (Sandberg, Maris & Hoogendoorn, 2014) (Wu, 2018) (Chen, Liu & Huang, 2019) (Fisser, Voogt & Bom, 2012), Spanish language learning (Holden & Sykes, 2011), Idioms (Amer, 2014), Vocabulary, Grammar, and Sentence Structure (Tsai et al., 2016), and Tenses, Words, Sentences (Önal, Çevik & Şenol, 2019). The results presented by studies for gamified applications of vocabulary learning, Idioms, grammar, sentence structure, tenses, and words outperformed the control groups with much engagement, interest, and positive feedback. Although mobile applications are effective, gamified applications are more effective with enhanced interest and engagement, resulting in positive learning outcomes (Ishaq et al., 2020a;Ishaq et al., 2020b;Ishaq et al., 2019;Ishaq et al., 2020d). Furthermore, it may be concluded that gamified applications are trending for all the subjects at all levels of education to get significant learning performance (Ishaq et al., 2020d) (Ishaq et al., 2020c;Dichev & Dicheva, 2017) (Zin & Yue, 2013;Zin, Jaafar & Yue, 2009). Furthermore,  recommended gamified application in the public sector school to effectively learn the English language (specifically reading comprehension at primary level) after addressing all the stakeholders' issues.

DISCUSSION AND FUTURE DIRECTIONS
This section summarizes and discusses the results related to the systematic literature review. The results showed that the performance in vocabulary acquisition and retaining by the experimental group was significantly higher. (Fisser, Voogt & Bom, 2012) 2013 Word Score Vocabulary learning School Mean, SD, t-test The results revealed teachers' and students' positive experiences and significant performance noted who played outside the class time. (Önal, Çevik & Şenol, 2019) 2019 SOS Table  Tenses

Taxonomic hierarchy
In this comprehensive literature review, the aim was to investigate current MALL information and its application with 63 selected papers. To achieve this objective, a taxonomic hierarchy of finalized studies shown in Fig. 8 was established and examined trends and perspectives on adapted/developed frameworks, content, and teaching and learning tools. However, these dimensions were further broken down into several sublevels that illustrated each area's scope with its role in enhancing the efficiency of language learners.

Future directions
It was suggested that MALL specific theories or models might be developed because the models used from fields other than MALL was to be adopted or adapted as all components of the models used in the studies could not be applied to measure the constructs. The researchers used varying theories or models to develop a theoretical framework of the respective studies, and this practice was too time-consuming, and the models were minimum valid. The researcher confronted the same issue while measuring usability, usefulness, effectiveness, ease of use, user-friendliness, and user behavior. To ensure the effectiveness of learning content used in mobile and gamified applications, it was suggested that duly approved content material, i.e., written or pictorial by the concerned authorities, was observed from the literature. Whereas specified and authentic learning content was missing, and desired learning outcomes were not achieved. More work is needed concerning teachers' professional development and exploration of their competencies in the field of MALL. The teacher-student relationship was inevitable regarding the teachinglearning process because it was the only source of incorporating various teaching methods and techniques to make learning effective (Omer, Farooq & Abid, 2020). In this regard, to compete for the world, teachers must link up with technological devices and gamified applications to engage their students in learning and entertainment to achieve a high learning outcome (Isa et al., 2019). The applications used for learning did not fulfill the requirements related to usability, usefulness, effectiveness, ease of use, user-friendliness, and user behavior, so it is proposed to develop gamified applications (serious game) having all features supporting the above constructs. From the literature review, a gamified application for English language learning at the primary level was lacking. Students of primary class levels loved to play more than indulging in books. A conventional environment made the students passive in the class and lessened their motivation level.
During the literature review, research work regarding development of gamified application for reading comprehension was lacking. No such conceptual model gamification has been developed which may be used for language learning with reference to cultural context. Assessment of grammar or vocabulary in MALL applications were found during literature review but were not as such advanced enough that might perform personalized assessment of students' learning outcomes. Same was found in case of reward system and entertainment elements.
Therefore, gamified learning applications may be designed for primary grade students to make language learning more enjoyable, entertaining, attractive, and engaging them to achieve high learning outcomes effectively.

CONCLUSION
This systematic literature review aimed to understand research patterns in MALL to learn the English language through mobile or gamified applications, approaches, and frameworks/models developed, or adopted. A comprehensive analysis of literature was undertaken to ensure a detailed discussion of the problems and their remedies. It was searched with as many known terminologies associated with MALL and then analyzed the results accordingly. The search was ended in August 2020, which would not have comprised studies that were carried out after the date. The Web of Science core collection was analyzed, and 63 out of 57,364 publications were selected.
The findings shown that nearly every selected article was published in a recognized journal, whereas only single research at a conference. The two primary forms of study adopted in these studies were "Solution Proposal" and "evaluation research". The majority of the chosen researches were evidence-based and could lead to the full advantages of MALL to teachers and students. MALL's most frequent key aspects were language learning strategies and evaluation of students' results. In contrast, MALL specific frameworks and theories, approved content were less addressed aspect of MALL.
The deficiencies in SLR related explicitly were research technique, incorrect data collection, or misclassification. However, with separate keywords from the Web of Science core collection repository, the research approach minimized the possibility of selection error. External concerns were addressed by implementing specific inclusion/exclusion guidelines, and two independent experts were requested to evaluate all extractions.
For future research on MALL, more attention might be paid to primary or secondary school students and teachers, approved curricula design for English subject, and tools' design, particularly serious games. Further evaluation research might be conducted to analyze existing MALL content.