Programming and Problem Solving — Software Engineering

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

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

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

4. Using OCD 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 thattemperature from the keyboard, compute thecorresponding Fahrenheit temperature, and display the result, along with a descriptive label on the screen. 4

5. Using OCD 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 thattemperature from the keyboard, compute thecorresponding Fahrenheit temperature, and display that temperature, along with a descriptive label on the screen. These make up the objects in our problem. 5

6. Using OCD Information about Objects Determine a type and a name (if necessary) for each object and whether it is a constant or a variable. cout cin 6

7. Using OCD Operations 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 thattemperature from the keyboard, compute thecorresponding Fahrenheit temperature, and display that temperature, along with a descriptive label on the screen. These make up the operations in our problem. 7

8. Using OCD 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

9. Using OCD 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

10. Using OCD Information about Objects (Revised) 10

11. Using OCD Information about Operations (Revised) 11

12. Using OCD Algorithm D. Organize the objects and operations into a sequence of steps that solves the problem, called an algorithm. 1. Display via coutinformation about the programto the user. 2. Display via couta 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

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. The Code /* 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 <iostream> // 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. } /* John Doe CS 104X Input: Output: -----------------------------------------------*/ #include <iostream> // cin, cout, <<, >> using namespace std; int main() { } When learning to program, it is helpful to just start with the algorithm as comments in main() 14

15. The Code /* 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 <iostream> // 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. cout << "John Doe CS 104X -- Lab 1\n\n"; cout << "** Convert Celsius temps to Fahrenheit **\n"; cout << "Please enter a temperature in Celsius: "; 15

16. The Code // 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. } double celsius; cin >> celsius; double fahrenheit = 1.8 * celsius + 32; cout << celsius << " degrees Celsius is " << fahrenheit << " degrees Fahrenheit.\n"; It’s wise to echo input data to insure computer read what you intended. 16

17. /* 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 <iostream> // 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: "; Comments Always begin a program with opening documentation enclosed in/* and */. 17

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 <iostream> // 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: "; LibrariesThis loads the C++ library that we need.Lab & Proj. 1: #include <cmath> 18

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 <iostream> // 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 statementsinside main()function. Why no \n ? 19

20. Always a goodidea to echoinput data Each step of the algorithm is implemented by one or more C++ program statementsinsidemain()function. // 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"; } Note spacing, indentation, & alignment to make program “look nice” and easier to read.This will be one criterion used in grading. 20

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. 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. 21

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. Why Testing is Important: 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. SeeOther Course Information (CS 104 page): • Importance of Program Testing — Horror Stories • 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. 23

24. Maintenance SeeOther Course Information (CS 104 page): • Time Spent on Program Maintenance • 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 24