Background. Readability and comprehension are the critical points of software developmentand maintenance. There are many researcher point out that the duplicatecode as a code smell has effect on software maintainability, but lack of research abouthow duplicate code affect software readability and comprehension, which are parts of maintainability. Objectives. In this thesis, we aim to briefly summarize the impact of duplicatecode and typical types of duplicate code according to current works, then our goalis to explore whether duplicate code is a factor to influence readability and comprehension. Methods. In our present research, we did a background survey to asked some background questions from forty-two subjects to help us classify them, and conduct an experiment with subjects to explore the role of duplicate code on perceived readability and comprehension by experiment. The perceived readability and comprehension are measured by perceived readability scale, reading time and the accuracy of cloze test. Results. The experimental data shows code with duplication have higher perceived readability and better comprehension, however, the difference are not significant.And code with duplication cost less reading time than code without duplication,and the difference is significant. But duplication type are strongly associate with perceived readability. For reading time, it is significant associate with duplication type and size of code. While there do not exists significant correlation between programmingexperience of subjects and perceived readability or comprehension, andit also has no significant relation between perceived readability and comprehension,size and CC according to our data results. Conclusions. Code with duplication has higher software readability according tothe results of reading time, which is significant. And code with duplication has highercomprehension than code without duplication, but the difference is not statistically significant according to our experimental results. Longer size of code will increasereading time, and different duplication type also influence the perceived readability,the three duplication types we discussed show these relationship obviously.

Reaktiv programmering är ett programmeringsparadigm som har utvecklats för att underlätta byggande av händelsedrivna reaktiva applikationer. Dess förespråkare hävdar att det kan leda till ökad kodkvalitet, men få studier har utförts för att underbygga dessa påståenden empiriskt. Denna studie syftade till att undersöka skillnaden i kodkomplexitet och kodläsbarhet mellan traditionell imperativ programmering och reaktiv programmering. En fallstudie utfördes där koden för ett befintligt öppen källkodsprojekt omstrukturerades, vilket resulterade i en imperativ version och en reaktiv version av samma kod. Verktyg för statisk källkodsanalys användes för att undersöka om några förändringar i kodläsbarhet och kodkomplexitet kunde upptäckas. Vidare diskuteras huruvida resultaten av den senaste teknikens läsbarhetsmätvärden ger en exakt förutsägelse av kodläsbarheten i reaktiva kodbaser, eller om kanske dessa mätvärden behöver modifieras för att göra dem tillämpliga på det reaktiva paradigmet. Våra resultat visar att läsbarheten påverkades negativt av reaktiv programmering när den mättes med senaste teknikens läsbarhetsmätvärden, men kodkomplexiteten minskades betydligt. / Reactive programming is a programming paradigm that has been proposed to facilitate building eventdriven reactive applications. It is claimed by its proponents to increase code quality, but few studies have been performed to substantiate these claims empirically. This study aimed to explore the difference in code complexity and code readability between traditional imperative programming and reactive programming. A case study was performed where the code of an existing open source project was restructured, resulting in an imperative version and a reactive version of the same code. Static analysis tools were used to investigate if any changes in code readability and code complexity could be detected. Furthermore, it is discussed whether the results of the state-of-the-art readability metrics give an accurate prediction of code readability in reactive code bases, or if perhaps these metrics need to be modified to make them applicable to the reactive paradigm. Our findings show that the readability was negatively affected by reactive programming when measured with state-of the-art readability metrics, however code complexity was decreased significantly