1. Programming and Problem Solving — Software Engineering (Read Chap. 2) 1

2. Problem Solving A Temperature-conversion problem: Write a program that, given a temperature in Celsius, displays that temperature in Fahrenheit. Implementation (Coding) Testing, Execution and Debugging Maintenance OCD (Object-Centered Design) 2 5 Phases of (Simplified) Software Life Cycle: Problem Analysis and Specification Design

3. OCD (Object-Centered Design) 1. 1.Describe the behavior of the program. 2. 2.Identify the problem’s objects and make a table of information about them. 3. 3.Identify the problem’s operations and make a table of information about them. 4. 4.Organize the objects and operations into a sequence of steps, called an algorithm, to solve the problem. 3

4. Behavior A. Describe the desired behavior of the program: Our program should display program information to the user and then a prompt for the Celsius temperature on the screen, read that temperature from the keyboard, compute the corresponding Fahrenheit temperature, and display the result, along with a descriptive label on the screen. 4 Using OCD

5. Problem Objects Problem Objects B. Identify the nouns in the behavioral description (other than "non-behavioral" ones like "program" and "user"): Our program should display program information to the user and then a prompt for the Celsius temperature on the screen, read that temperature from the keyboard, compute the corresponding Fahrenheit temperature, and display that temperature, along with a descriptive label on the screen. These make up the objects in our problem. 5 Using OCD

6. cout cin Information about Objects Determine a type and a name (if necessary) for each object and whether it is a constant or a variable. 6 Problem Object Type Kind Name program informationtextconstant none prompttextconstant none Celsius temperaturereal number variable celsius screenoutputvariable keyboardinputvariable Fahrenheit temperaturereal number variable fahrenheit labeltextconstant none Using OCD C++ Type ? ? double ? ? ?

7. Operations These make up the operations in our problem. C. Identify the verbs in the behavioral description: Our program should display program information to the user and then a prompt for the Celsius temperature on the screen, read that temperature from the keyboard, compute the corresponding Fahrenheit temperature, and display that temperature, along with a descriptive label on the screen. 7 Using OCD

8. Information about Operations Identify the C++ operator to perform a given operation, if there is one.. To compute the Fahrenheit temperature, we need to know/find the Celsius to Fahrenheit conversion formula. 8 Operation Pre- defined? C++ OperatorLibrary Displayyes <<iostream Readyes >>iostream Compute the Fahrenheit temperature ?? Using OCD

9. Celsius-to-Fahrenheit Formula for converting Celsius to Fahrenheit: fahrenheit = 1.8 × celsius + 32 Converting the temperature thus adds new objects and operations to our problem. 9 Using OCD

10. Information about Objects (Revised) 10 Problem Object Type Kind C++ Type Name program informationtextconstant ? none prompttextconstant ? none Celsius temperature real number variable doublecelsius screenoutputvariable ?cout keyboardinputvariable ?cin Fahrenheit temperature real number variable doublefahrenheit labeltextconstant ? none conversion factor 1.8 real number constant double none conversion factor 32 integer constant int none Using OCD

11. Information about Operations (Revised) 11 Operation Pre- defined? C++ OperatorLibrary Displayyes <<iostream Readyes >>iostream Compute the Fahrenheit temperature: Multiply two real values (1.8 and celsius) yes * built-in Add a real value (the result above) and an integer (32) yes + built-in Store a real value (the result above) in a variable yes = built-in Using OCD

12. Algorithm D. Organize the objects and operations into a sequence of steps that solves the problem, called an algorithm. 1. Display via cout information about the program to the user. 2. Display via cout a prompt for the Celsius temperature. 3. Read the temperature from cin. 4. Compute the Fahrenheit temperature from the Celsius temperature. 5. Display via cout the Fahrenheit temperature and an informative label. 12 Using OCD

13. Coding Once we have designed an algorithm, the next step is to translate that algorithm into a high level language like C++. This involves writing instructions to — represent the objects, and — perform the operations in C++. 13

14. 14 The Code When learning to program, it is helpful to just start with the algorithm as comments in main() /* John Doe CS 104X Input: Output: -----------------------------------------------*/ #include // cin, cout, > using namespace std; int main() { } /* temperature.cpp converts a Celsius temperature to Fahrenheit. John Doe Lab 1 Jan. 5, 2012 CS 104X Input: A Celsius temperature Output: Corresponding Fahrenheit temperature -----------------------------------------------*/ #include // cin, cout, > using namespace std; int main() { // 1. Display via cout information about the // program to the user. // 2. Display via cout a prompt for the Celsius // temperature. // 3. Read the temperature from cin. // 4. Compute the Fahrenheit temperature from the // Celsius temperature. // 5. Display via cout the Fahrenheit temperature // and an informative label. }

15. cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n"; cout << "Please enter a temperature in Celsius: "; 15 /* temperature.cpp converts a Celsius temperature to Fahrenheit. John Doe Lab 1 Jan. 5, 2012 CS 104X Input: A Celsius temperature Output: Corresponding Fahrenheit temperature -----------------------------------------------*/ #include // cin, cout, > using namespace std; int main() { // 1. Display via cout information about the // program to the user. // 2. Display via cout a prompt for the Celsius // temperature. The Code

16. double celsius; cin >> celsius; double fahrenheit = 1.8 * celsius + 32; cout << celsius << " degrees Celsius is " << fahrenheit << " degrees Fahrenheit.\n"; 16 // 3. Read the temperature from cin. // 4. Compute the Fahrenheit temperature from the // Celsius temperature. // 5. Display via cout the Fahrenheit temperature // and an informative label. } The Code It’s wise to echo input data to insure computer read what you intended.

17. 17 Comments /* temperature.cpp converts a Celsius temperature to Fahrenheit. John Doe Lab 1 Jan. 5, 2012 CS 104X Input: A Celsius temperature Output: Corresponding Fahrenheit temperature -----------------------------------------------*/ #include // cin, cout, > using namespace std; int main() { // 1. Display via cout information about the // program to the user. cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n"; // 2. Display via cout a prompt for the Celsius // temperature. cout << "Please enter a temperature in Celsius: "; Always begin a program with opening documentation enclosed in /* and */.

18. /* temperature.cpp converts a Celsius temperature to Fahrenheit. John Doe Lab 1 Jan. 5, 2012 CS 104X Input: A Celsius temperature Output: Corresponding Fahrenheit temperature -----------------------------------------------*/ #include // cin, cout, > using namespace std; int main() { // 1. Display via cout information about the // program to the user. cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n"; // 2. Display via cout a prompt for the Celsius // temperature. cout << "Please enter a temperature in Celsius: "; 18 Libraries This loads the C++ library that we need. Lab & Proj. 1: #include

19. 19 /* temperature.cpp converts a Celsius temperature to Fahrenheit. John Doe Lab 1 Jan. 5, 2012 CS 104X Input: A Celsius temperature Output: Corresponding Fahrenheit temperature -----------------------------------------------*/ #include // cin, cout, > using namespace std; int main() { // 1. Display via cout information about the // program to the user. cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n"; // 2. Display via cout a prompt for the Celsius // temperature. cout << "Please enter a temperature in Celsius: "; Each step of the algorithm is implemented by one or more C++ program statements inside main() function. Why no \n ?

20. 20 // 3. Read the temperature from cin. double celsius; cin >> celsius; // 4. Compute the Fahrenheit temperature from the // Celsius temperature. double fahrenheit = 1.8 * celsius + 32; // 5. Display via cout the Fahrenheit temperature // and an informative label. cout << celsius << " degrees Celsius is " << fahrenheit << " degrees Fahrenheit.\n"; } Each step of the algorithm is implemented by one or more C++ program statements inside main() function. Note spacing, indentation, & alignment to make program “look nice” and easier to read. This will be one criterion used in grading. Always a good idea to echo input data

21. Testing Run your program using sample data (whose correctness is easy to check): John Doe CS 104X -- Lab 1 ** Convert Celsius temps to Fahrenheit ** Please enter the temperature in Celsius: 0 0 degrees Celsius is 32 degrees Fahrenheit. 21 John Doe CS 104X -- Lab 1 ** Convert Celsius temps to Fahrenheit ** Please enter the temperature in Celsius: 100 100 degrees Celsius is 212 degrees Fahrenheit.

22. When you are convinced that the program is correct, run it with the required data values. John Doe CS 104X -- Lab 1 ** Convert Celsius temps to Fahrenheit ** Please enter the temperature in Celsius: -17.78 -17.78 degrees Celsius is -0.004 degrees Fahrenheit. 22

23. 23 For a programming assignment: Lose a few points or may be lucky and the grader doesn’t catch it. For a real-world problem: Much more may be at stake: money, jobs, and even lives. Why Testing is Important: September,1999: Mars Climate Orbiter June, 1996: Ariane 5 rocket March,1991: DSC Communications February 25, 1991(Gulf War): Patriot missile Testing is never finished; it is only stopped. Testing can only show the presence of errors, not their absence. See Other Course Information (CS 104 page): Importance of Program Testing — Horror Stories Importance of Program Testing — Horror Stories

24. Maintenance 24 Large % of computer center budgets Large % of programmer's time Largest % of software development cost Why? Poor structure, poor documentation, poor style ⇒ ⇒ less likely to catch bugs before release ⇒ ⇒ fixing of bugs difficult and time-consuming ⇒ ⇒ impede implementation of enhancements See Other Course Information (CS 104 page): Time Spent on Program MaintenanceTime Spent on Program Maintenance