Problem Solving and Software Engineering Chapter 1 C

Problem Solving and Software Engineering Chapter 1 C++, An Introduction to Computing, 3 rd Ed.

2 Objectives Indicate uses of computers First look at a C++ program Basic phases of software life cycle • Object-centered design Issues, ethical principles First look: classes and object-oriented design C++, An Introduction to Computing, 3 rd Ed.

3 Uses of Computers Industry • Robots, CAD, project management and control Government • Defense, space, compile data, weather Medicine • Medical records, life support systems, CAT scan, MR scan Entertainment • Animation, colorization, special effects Science • Simulations, molecule analysis, food quality testing Information Technology • Digital libraries, online art C++, An Introduction to Computing, 3 rd Ed.

4 What is Programming? Computer Program • A sequence of statements that instruct a computer in how to solve a problem. Programming • The act of designing, writing and maintaining a program Programmers • People who write programs C++, An Introduction to Computing, 3 rd Ed.

5 The World of C++ Sample program Comment /* greeting. cpp greets its user. * * Input: The name of the user * Output: A personalized greeting *****************************/ #include <iostream> // cin, cout, <<, >> #include <string> // string Compiler using namespace std; Specifies standard int main() directives related names { cout << "Please enter your first name: "; string first. Name; cin >> first. Name; cout << "n. Welcome to the world of C++, " << first. Name << "!n"; } Main portion of program. Contains C++ statements. C++, An Introduction to Computing, 3 rd Ed.

6 The World of C++ statements Output statement int main() Variable to prompt user { declaration cout << "Please enter your first name: "; string first. Name; cin >> first. Name; cout << "n. Welcome to the world of C++, " << first. Name << "!n"; Input from keyboard } Output character string and value stored in variable C++, An Introduction to Computing, 3 rd Ed.

7 Problem Solving through Software Engineering Phases Design • Analysis, specify algorithms to solve problem Coding • Write solution in syntax of language Testing, Execution, Debugging • Get rid of “bugs” Maintenance • Update, modify to meet changing needs C++, An Introduction to Computing, 3 rd Ed.

8 Problem World’s largest ball of twine found in Cawker City, Ks. • How much does the ball weigh? • How many miles would the twine reach if unrolled? C++, An Introduction to Computing, 3 rd Ed.

9 Object-Centered Design Steps State how you want the program to behave Identify real-world objects, categorize Identify operations needed to solve the problem Develop algorithm – arrange objects, operations in an order which solve the problem C++, An Introduction to Computing, 3 rd Ed.

10 Behavior To find the weight of a ball of string: Enter radius of sphere : 9 Now computing. . . Weight of ball of string = 999. 99 C++, An Introduction to Computing, 3 rd Ed.

11 Objects Description Software Objects Type Kind Name prompt for radius of sphere string constant none ostream variable cout double variable radius istream variable cin double variable weight screen radius of sphere keyboard weight of ball C++, An Introduction to Computing, 3 rd Ed.

12 Operations Output prompt for radius of sphere to cout Input real value from cin Store it in radius Compute weight Output weight to cout C++, An Introduction to Computing, 3 rd Ed.

13 More Objects Computation of weight requires additional objects W=density * 4 (π r^3 )/3 Description Software Objects Type Kind Name density of sphere double variable 4. 0 double constant π double constant 3 integer constant double constant 3. 0 C++, An Introduction to Computing, 3 rd Ed. density PI

14 Algorithm 1. Initialize constant PI 2. Output prompt for radius to cout 3. Input real value from cin, store in radius 4. Output prompt for density to cout 5. Input real value from cin, store in density 6. Compute 7. Output weight to cout C++, An Introduction to Computing, 3 rd Ed.

15 Coding First, create a program stub that contains opening documentation • Compiler directives that add items in libraries needed for some of the • Objects and operations • An empty main function Convert each step of the algorithm into code. • If it uses a software object that hasn’t already been declared, add a declaration statement that specifies the object’s type and name. C++, An Introduction to Computing, 3 rd Ed.

16 Coding /* sphere. Weight. cpp computes the weight of a sphere. * * Input: The radius (feet) and * the density (pounds/cubic foot) of a sphere * Output: The weight of the sphere (pounds) ************************/ #include <iostream> // cin, cout, <<, >> #include <cmath> // pow() using namespace std; int main() { } C++, An Introduction to Computing, 3 rd Ed.

17 Coding int main() { const double PI = 3. 14159; cout << "Enter the sphere's radius (feet): "; double radius; cin >> radius; cout << "Enter its density (pounds/cubic feet): "; double density; cin >> density; double weight = density * 4. 0 * PI * pow(radius, 3) / 3. 0; cout << "n. The weight of the sphere is approximately " << weight << " pounds. n"; } C++, An Introduction to Computing, 3 rd Ed.

18 Testing Enter radius of sphere (feet) : 6. 5 Enter its density (pounds/cubic feet) : 14. 6 The weight of the sphere is approximately 16795 pounds C++, An Introduction to Computing, 3 rd Ed.

19 Testing, Execution, Debugging Common error sources Violations of grammar rules of the high level language Errors that occur during execution Errors in the design of the algorithm C++, An Introduction to Computing, 3 rd Ed.

20 Syntax Errors Example: double radius • Missing semi-colon Compiler finds most of these kinds of errors Different compilers give varying degrees of helpful diagnostics C++, An Introduction to Computing, 3 rd Ed.

21 Run Time Errors Not detected until program runs Examples • Division by zero causes program to crash • Taking square root of negative causes program crash Program must be modified to keep such events from happening C++, An Introduction to Computing, 3 rd Ed.

22 Logic Errors Program compiles, runs without crashing, but gives incorrect results These are hardest errors to find Find by using sample data and hand calculating the correct results, comparing Note: Testing grows increasingly more difficult with larger programs • Some will run for years without logic error appearing C++, An Introduction to Computing, 3 rd Ed.

23 Maintenance Student programs run only a few times Real-world programs used for many years • Due to significant investment of resources New features may be required during life of program usage Upgrading called “maintenance” C++, An Introduction to Computing, 3 rd Ed.

24 Problem Sam Splicer installs coax cable for Metro Cable Co. Basic service charge $25. 00 Additional $2. 00 for each foot of cable Company Pres. wants to compute revenue generated by Sam for given month Example: 263 yards of cable at 27 locations generates $2253. 00 in revenue C++, An Introduction to Computing, 3 rd Ed.

25 Describe Behavior of Program should display prompt for number of installations performed and total number of yards of cable installed User enters values from keyboard Program computes, displays on screen total amount of revenue resulting from these installations C++, An Introduction to Computing, 3 rd Ed.

26 Behavior Envisioned To determine revenue generated, Enter number of installations : 27 Enter number of yards of cable installed : 263 Total revenue generated is $2253. 00 C++, An Introduction to Computing, 3 rd Ed.

27 Objects Use description to fill in chart for objects. Description Software Objects Type Kind Name C++, An Introduction to Computing, 3 rd Ed.

28 Operations Use description to fill in chart for operations. Description Name Predefined? Library C++, An Introduction to Computing, 3 rd Ed. Operator

29 Algorithm and Coding Work together to determine the steps necessary to have the objects manipulated by the operations Write the source code • Compile and Link • Test the program C++, An Introduction to Computing, 3 rd Ed.

30 Ethics and Issues Consider the essay by Professor Anne Marchant (see web site of text) • • • Ethics and Society Computer Crime and Security Health Concerns and the Environment Information Ownership “Netiquette” and Hoaxes Internet Content and Free Speech Privacy Quality Control and Risk Reduction The Future C++, An Introduction to Computing, 3 rd Ed.