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Understanding Functional Decomposition in Programming

This unit emphasizes the importance of functional decomposition in programming. It explains the drawbacks of writing long code in a single main method, illustrating how it complicates management. By breaking down problems into smaller, manageable pieces, programmers can leverage methods to write code incrementally and collaboratively. The concept mimics human memory patterns, allowing improved understanding and recall of information. The example provided showcases a main method that effectively utilizes functional decomposition to streamlining program development.

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Understanding Functional Decomposition in Programming

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  1. Functional Decomposition

  2. At the beginning of this unit we discussed how most of your programs have been written like this: public class BigProgram { public static void main (String [ ] args) { statement; statement; statement; statement; statement; statement; statement; statement; statement; statement; statement; statement; } }

  3. There are problems with writing all of the code in the main method: • Programs can get very long. The longer they are the harder they are to manage. • Human beings are not computers. We don’t see information as a whole like a computer.

  4. Human beings “chunk” data. For example, try memorizing the following number: 7743125039

  5. What is that number?

  6. Now, let’s divide that number into chunks: 774 – 312 - 5039 • Try memorizing that number now.

  7. What is that number?

  8. Chances are you were able to memorize it that time because you “chunked” the data. • Programmers do the same thing when they design and develop programs. • Functional Decomposition: • The process of breaking a problem into smaller pieces.

  9. Functional Decomposition has advantages in programming: • The best way to solve a complex problem is to break it down into smaller problems. • Using methods, specific parts of a problem can be written at one time. You don’t have to worry about the whole program. • Methods allow the program to be broken up so multiple people can work on ONE program.

  10. main method • Again, this is what a program looks like when it is broken up into smaller methods: public class DividedProgram { public static void main (String [ ] args) { statement; statement; } public static void method2( ) { statement; statement; } public static void method3( ) { statement; statement; } public static void method4( ) { statement; statement; } } method 2 method 3 method 4

  11. Here is an example of a main method that uses functional decomposition to call other methods: public static void main(String[] args) throws IOException { int intNumDays = 30; // Number of days of sales String strFileName; // The name of the file to open double dblTotalSales; // Total sales for period double dblAverageSales; // Average daily sales // Get the name of the file. strFileName = getFileName(); // Get the total sales from the file. dblTotalSales = getTotalSales(strFileName); // Calculate the average. dblAverageSales = calcAverageSales(dblTotalSales, intNumDays); // Display the total and average. displayResults(dblTotalSales, dblAverageSales); System.exit(0); }

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