Understanding Nested If-Else, Boolean Types and Switch Statements in C++

1. Quiz 1 Exam 1 Next Week

2. Nested if Statements if (myGrade >= 80) if (myGrade >= 90) cout << “You have an A!” << endl; else cout << “You have a B!” << endl; else cout << “We’ll give you a C.” << endl;

3. if/else (Cascaded) • Sequence of if/else Statements • Example: if (myGrade > 90) cout << “A!” << endl; else if (myGrade > 80) cout << “B!” << endl; else if (myGrade > 70) cout << “C!” << endl; else cout << “Oh-oh!” << endl;

4. Boolean Type • A Boolean Value Is One of Either “True” or “False” • In C++, Type bool • Example: bool done = false; . . . if (currentLetter == ‘Z’) done = true; else done = false; … if (done) return(0); . . . • if/else Conditionals Must Evaluate to True or False, and Are Therefore Called Boolean Expressions • In C++, Any Non-Zero Value Is Considered True; Any Expression Evaluating to Zero Is Considered False

5. Logical Operators • A Logical Operator Is One Used to Further Specify True or False in an Expression • Connects Two or More Expressions Together • && Is Logical “AND” • || Is Logical ‘OR” • &&: Both Operands Must Be True for Entire Expression to Be True • ||: Only One (or Both) of the Operands Must Be True for Entire Expression to Be True

6. Logical Operators if (numStudents > MIN && numStudents < MAX) classRun = true; if (numStudents > MAX || numInstructors == 0) classRun = false;

7. Operator Precedence • () • ! (not) • *, /, % • +, - • <, <=, >, >= (Relational Operators) • ==, != (Equality Operators) • && (Logical AND) • || (Logical OR) • = (ASSIGNMENT)

8. Order of Operations • Precedence: Level of Importance of Operations Multiplicative Operators Have Higher Precedence than Additive Operators: *, /, % Higher +, - Lower • Associativity: Order of Operation for Equal Level Precedence Most Operators Have Left-to-Right Associativity Use Parentheses to Force Differing Precedence of Operations

9. Multiple Logical Operators if ( num1 > MAX || num2 == 0 && num3 == 0) cout << “num1 is MAX or something is 0”; cout << “I think…..” << endl;

10. Switch Statements • Also Called Switch/Case Statement • Just Case in Other Languages • Selects Among Several Different Actions • Can Only Select from Integer or Character • If an Integer Value Is Matched, Statements under Control of that Case Block Are Executed

11. Switch/Case Example const double BASERATE = 104.50; double rate; int numPassengers; cout << “Enter Passengers: “; cin >> numPassengers; switch(numPassengers) { case 2: rate = BASERATE * 0.80; break; case 4: rate = BASERATE * 0.75; break; case 5: rate = BASERATE * 0.55; break; default: rate = BASERATE; break; }

12. Switch Case Example char menuItem; cout << "Enter Menu Selection: "; cin >> menuItem; switch(menuItem) { case 'O': case ‘o': /* code to do ordering goes here*/ break; case 'C': case ‘c': /* code to do checkout goes here*/ break; default: cout << “Unknown option” << endl; break; }

13. Announcements • Exam 1 Next Week in Lecture • Everything through Lab 4 • 50 minutes • 10 % of Total Grade • Covers Everything through Lecture this Week • Quiz 1 Topics (terminology, variables, constants, basics) • if-then-else • Compound statements • Relational operators • Logical operators • Switch/Case Statements