Back to the Basics: Using Flowcharts in the Classroom

Transcription

1 Back to the Basics: Using Flowcharts in the Classroom Mark S. Hall Assistant Professor of Computer Science Computer Science, Engineering, Physics & Astronomy (CSEPA) University of Wisconsin Marathon County (UWMC) University of Wisconsin - Colleges Wausau, WI mark.hall@uwc.edu Abstract Students struggle with developing algorithms to solve problems. Languages that are used in introductory courses introduce syntax issues that create additional problems for students. With the advent of the internet, more and more students are visual learners and languages that are textbased like Java and C++ do not help these students. Learning programming skills are very similar to learning mathematical skills in that students learn more if asked to write more programs. The numbers of in-class programming activities that can be accomplished in a single lecture are limited to the syntactical nature of the current language of choice. Textbooks introduce pseudocode and flowcharts as design tools to assist in the development of algorithms. Yet the use of the standard flowchart template along with paper and pencil can be a very frustrating & cumbersome process. The Visual Logic application uses flowchart symbols to help students create algorithms to solve problems electronically. This tool aids in the cyclical nature of the algorithm development process as changes can be made rapidly to test new ideas. This rapid development also allows instructors and/or students to develop more algorithms individually, or in groups, in a single lecture. Page 1 of 9

2 1 Introduction Shackelford and LeBlanc [1] previously observed that the use of a particular programming language in an introduction to computing course tends to annoy and distract attention for students away from finding an algorithm that solve a particular problem. From my seven years of Computer Science teaching experience, it has been my observations that students in my classroom struggle to create the algorithms to solve programming problems that I assign, let alone handle the nuances of learning the syntax of any formal programming language. As the frustrations mounted for me as I taught programming courses, I kept searching for ways to help students become more successful writing algorithms to solve simple problems, let alone any complex ones. Despite my preaching of using the design tools of pseudocode and flowcharts (that are documented in most textbooks) prior to coding, I knew, and students were always confirm, that these words went in one ear and out the other. During my travels, I found an electronic flowcharting tool (Visual Logic) that allowed algorithms to be created using common flowchart symbols, and that allowed the algorithm to be executed to verify a valid solution. Classroom observation and antidotal evidence supports that the use of this tool did improve student s algorithm solving abilities. 1.1 Background The thirteen 2-year University of Wisconsin (UW) Colleges serve students over the entire state of Wisconsin [2]. The Computer Science (CS) program in the UW Colleges is designed to be easily transferable to the 4-year institutions within the UW System. The nationwide decline in CS enrollments reported in the Taulbee Survey [3] has affected the UW System, and has been particularly hard on the 2-year UW Colleges (UWC), which are relatively small colleges, with a combined enrollment of approximately 12,00 students. In addition, the majority of our students are in the bottom 60% of their high school rank. The majority of our students enroll to prove that they can achieve at the University level in order to be accepted at a 4-year University. 1.2 Enrollment Issues A trend of declining enrollment in Computer Science (CS) is being felt at the 2-year University of Wisconsin (UW) Colleges, as is the case nationally. UWMC is the third largest two-year campus in the UW Colleges [4]. A course titled CPS 110 Introduction to Computer Science (Visual Basic.Net) is offered for non-majors, and the majority of those students, provide the pool of students that need to be recruited to help the enrollment numbers for the core Computer Science classes that are offered. The initial enrollment for the past five sections of the CPS 110 courses that I have taught consisted of 7, 8, 15, 17, and 7 students. It is safe to say that those are NOT the numbers that were active in the classroom at the end of the semester. The loss of these potential students for the core Computer Science courses were very troubling. Many research articles have documented that students struggle with learning the syntax of programming languages. Something needed to be done to recruit and then retain these students. 2 Flowcharts as a Design Tool Page 2 of 9

3 The main problems students have in this course are their inability to be able to solve problems. The lack of critical thinking skills hinders their ability to be successful when writing basic algorithms to solve problems. In fact, that is the hardest part of writing any programming assignment for beginning students. Once the algorithm is found, for most students, the implementation of the algorithm in any language is relatively simple. 2.1 Designing Algorithms and Critical Thinking Skills As I looked at the guidelines established by the UW Colleges for teaching the general concepts for this course, the emphasis that course coverage for designing algorithms should take at least a minimum of two hours. And the reality is that every programming assignment typically forces students to design a totally different algorithm. In order to be successful in this course, for the students and the professor, somehow, someway, the critical thinking skills of students have to be improved. Improvements in critical thinking along with the understanding of the basic control structures will allow students to be successful writing simple programs using any language. 2.2 Flowchart Template The majority of any 40+ Computer Science professors remember the day when their college professors enforced algorithm design by mandating that CS students turn in their flowcharts which represented the solution to a problem. Flowcharts, along with pseudo-code were recognized as design tools that students could use to create a successful algorithm. Syllabi specified that the flowchart template was a mandatory purchase at the local campus bookstore (Figure 1). Figure1: Flowchart Template These professors also remember assignments that started out looking like majestic creations of art, and turned into crumpled balls of paper used as basketballs to shoot at the closet wastebasket. Any change to an algorithm meant erasing and modifying the flowchart symbols that were squished onto a sheet of paper. After several changes, the paper was no longer useable, and the complete algorithm had to be re-drawn from the beginning. The frustration levels of future CS leaders rose to all-time levels. Yes, flowcharting can be a very valuable visual tool that supported algorithmic design. But the tool was very primitive and very time-consuming. Is there a better way to use the same concept but make it electronic and interactive which would aid students to develop successful algorithms that proved to be solutions to problems? Yes, there is! Page 3 of 9

4 In an attempt to improve the success of algorithm design by the students, I recently began using the Visual Logic TM Flowchart Simulation Tool [5] introduced by Thad Crews and Chip Murphy, which is distributed with their textbook, Programming Right From the Start with Visual Basic.Net. Visual Logic TM allows students to develop algorithms that incorporate fundamental programming concepts using the flowcharting symbols electronically making it very easy to make changes to the algorithm. The unique attribute to this software is that the flowchart is executable so that the students can quickly and easily test their algorithm. Once their algorithm has been tested, then they can start the implementation of the algorithm using Visual Basic. 2.3 Related Work Using Flowcharting Tools A structured flowchart editor (SFC) was developed by Tia Watts in 2003 [6]. SFC allows the user to develop a flowchart. In addition, the tool always displays a textual representation of the flowchart in either a C or Pascal-like syntax. A disadvantage of the tool was that the user is required to copy and paste the textual representation into a text editor in order to make any changes to get a complete program. BACCII++, an iconic programming language, was developed by Calloni and Bagert (1997) [7]. BACCII++ was used to supplement their CS1/CS2 sequence which used C++. Students who used both BACCII++ and C++ were found to perform better than those students who only used C++. Code can be generated by the tool for any one of five text-based languages (including Pascal and C++) once the algorithm has been developed. To eliminate the shortfalls that these tools created where students had to debug the textual code, Crews and Zeigler (1998, 1999) developed the FLINT program [8]. The FLINT program forces students to use top-down design, and then design flowcharts for each sub module. These flowcharts are then executed within the FLINT program. 2.4 Visual Logic Visual Logic uses VB.NET syntax with an emphasis on designing and developing graphical, event-driven programs. Key introductory Computer Science concepts that can be introduced with the use of this tool includes the use variables, input, assignment statements, output, relational operators, boolean operators, the control structures of sequence, selection and repetition, sub and function procedures, arrays, and files. The easiest way to show the Visual Logic tool is visually. Figure 2 depicts the flowchart for the legendary Hello World program that seems to be introduced in most introductory programming textbooks. Page 4 of 9

5 Figure 2: Hello World Flowchart Visual Logic displays output using a MsgBox (Figure 3) or via a console window (Figure 4). Figure 3: MsgBox Figure 4: Console Window The insertion of flowcharting symbols is done via a pull-down menu (Figure 5). Figure 5: Symbol Menu Page 5 of 9

6 Figure 6 shows the flowchart for a basic algorithm that given two numbers will calculate the sum, difference, product, quotient, and average of those two numbers. 3 Using Visual Logic Figure 6: Basic Algorithm Flowchart Since Visual Logic uses VB.Net syntax, it is a natural fit for introductory programming courses that are taught using Visual Basic.Net. The introductory programming course consists of two credits of programming and one credit of basic computer concepts. 3.1 In-class Exercises For every major concept introduced, I try to create two to three Visual Logic programs, by myself with student help, or by a student with student help, or by letting students work in groups, or individually. These programs are not graded but provide an instructor with plenty of opportunities to discuss algorithms and possible pitfalls for each algorithm introduced, including the use of bad data. Page 6 of 9

7 3.2 Out-of-class Programming Assignments I will usually assign one or two problems where students will turn in Visual Logic solutions. Then I will assign another problem where students must create two solutions, one using Visual Logic, and then a solution using Visual Basic.Net which implemented the Visual Logic design. Thus I am forcing students to use a design tool prior to actual coding in Visual Basic. 4 Visual Logic Results 4.1 Student Survey In order to assess the value of using Visual Logic, I created a survey which I administered to the students that were enrolled in my Spring and Fall 2006 courses. The survey consisted of 5 questions each with a five-point scale (1-Strongly Disagree 3-Neutral 5-Strongly Agree). Table 2 shows the questions and the average scores. Survey Question Spring 2006 Fall ) I had few problems learning how to use VL to create my programs ) VL helped me to develop and improve my problem solving skills ) VL helped me to better understand how computer programs operate ) I had few problems getting my programs to run in VB once I had created them in VL ) I enjoyed programming in VL Table 2: Visual Logic Survey Results Survey Questions The survey results support that students do not have problems using Visual Logic and that students also felt that the tool helped them to develop and improve their problem solving skills. In addition, students also enjoyed using the tool which should help increase their use of the tool to design algorithms. 4.2 Instructor Observations The use of Visual Logic has allowed me to rapidly create algorithms that cannot be done in the same amount of time if I just used the Visual Basic.Net language. Syntax is not a problem for the students. Visual Logic is primarily used to cover the control structures of sequence, selection, and repetition. This tool has allowed me to cover more algorithms and more unique algorithms quicker and with less student frustration. At times in the lecture part of the course, every student in interacting with Visual Logic which keeps them focused and entertained. Since I teach at a small school with lower enrollments, I will never have enough students to ever attempt proper research to test how effective the use of this Visual Logic tool aids in the learning Page 7 of 9

8 of these concepts for the students. However, I have plenty of antidotal evidence from the student statements that allow me to have confidence that the tool is effective. Students state that they enjoy using Visual Logic as they can modify algorithms quickly to get immediate feedback. Students have stated that when they are using Visual Logic in the classroom, they never have a chance to get bored or fall asleep since they are being engaged. Two semesters ago, when I assigned the last Visual Basic programming assignment for the semester, I had a unique experience with a female student. After reading the specifications for the assignment, she blurted out that this assignment would be easier to do in Visual Logic than Visual Basic. As I looked at her, I could see some frustration in her expression. I quickly reminded her that flowcharts are a design tool that can always be used to aid in the development of algorithms so she could use Visual Logic. 4.3 Problems using Visual Logic Any attempt to solve complicated algorithms is really not aided by the use of Visual Logic. A complex algorithm results in a complex flowchart which cannot be viewed on the screen without the use of horizontal and vertical scroll bars in order to see the entire algorithm. There is a feature in Visual Logic that hampers use in the classroom. The for loop allows variables to be used for the start, finish and step values. However, if the step value is negative, the counting loop does not work as expected. 5 Conclusions The use of a flowchart application like Visual Logic provides an easy-to-use tool for students and instructors to experiment with developing algorithms quicker. Antidotal evidence from students supports the use of the flowcharts for designing algorithms, but only if done electronically. The visual nature of flowcharts allows for students to understand the control flow in their programs which makes it easier and less frustrating for them to solve problems. Antidotal evidence also indicates that teaching programming using an electronic flowcharting program like Visual Logic helps students develop their problem solving skills better than teaching programming using languages like Java, C++, or Visual Basic. However, the use of Visual Logic is just one of many tools that instructors can use to help students comprehend the many concepts in introductory Computer Science courses. Classroom observation and antidotal evidence supports that forcing students to use this tool did improve their algorithm solving abilities. And as an instructor, the tool allows quicker development of algorithms during lectures that allow more problems to be solved during each lecture and during the semester. Flowcharts have been around for many decades and have been specified as a design tool for many textbooks. The use of Visual Logic allows students to easily and quickly use flowcharts as a design tool. Students now can design algorithms using flowcharts without the side effect of the tool increasing their frustration level. From my point of view, Visual Logic aids student learning for introductory Computer Science concepts. Page 8 of 9

9 References [1] Shackelford, R., and LeBlanc, R. Introducing Computer Science Fundamentals Before Programming. Proceedings of FIE 97, [2] UW System, Two-Year Campuses [3] Zweben, S., Taulbee Survey, Computing Research News, Vol. 17/No.3, May [4] UW - Colleges [5] Visual Logic TM - Textbook Version Vanguard Computer Systems [6] Watts, T. (2003). SFC - A Structured Flow Chart Editor Version 3. Faculty Poster SIGCSE Available at: [7] Calloni, B. (1997). Iconic Programming Proves Effective for Teaching the First Year Programming Sequence. Proceedings of the 28th SIGCSE Symposium, [8] Crews, T., and Ziegler, U. (1998). The Flowchart Interpreter Programming Courses. Proceedings of FIE '98, Page 9 of 9