Decisions Given hours worked and pay rate, calculate total pay What if you work overtime? How do you indicate if your work overtime? How about double overtime? COSC175-Selection

Relational Operators < less than <= less than or equal to > greater than >= greater than or equal to == equals != not equal to COSC175-Selection

Examples 10 > 2 'a' < 'c' Why is this true? x != y temp > humidity num == 35 initial != ‘Q’ COSC175-Selection

Logicals: AND && OR || NOT ! COSC175-Selection

Examples 1. if ((sex == 'F') && (city_code == 18) && (gpa >= 3.7)) cout << "Merit Award" << endl; 2. if ((zip == "48002") || (zip == "48003") || (zip == "48004")) cout << "LOCAL“ << endl; COSC175-Selection

“Short-Circuit” Evaluation Process in which the computer evaluates a logical expression from left to right and stops as soon as the value of the expression is known one True in || -> True one False in && -> False Example: int age; int height; age = 25; height = 70; ((age > 50) && (height > 60)) 2. ((height > 60) || (age > 40))

Selection/Decision Test – true or false One operation performed if true One operation performed if false Keywords if, else COSC175-Selection

if Syntax if ( Expression ) statement NOTE: statement can be a single statement, a null statement, or a compound statement. COSC175-Selection

if statement is a selection of whether or not to execute a statement (which can be a single statement or an entire block) TRUE expression FALSE statement COSC175-Selection

Examples if (taxCode == ‘T’ ) price = price + taxRate*Price; 2. if (num < 0 ) { // compound statement cout << "Negative" << endl; numNegs = numNegs + 1; } 3. if (age < 21 ) cout << "Under Age" COSC175-Selection

if-else Syntax NOTE: StatementA and StatementB each can be if ( Expression ) StatementA else StatementB NOTE: StatementA and StatementB each can be a single statement a null statement, or a compound statement. COSC175-Selection

if..else provides two-way selection between executing one of 2 clauses (the if clause or the else clause) TRUE FALSE expression if clause else clause COSC175-Selection

int carDoors, driverAge; float premium, monthlyPayment; . . . if ( (carDoors == 4 ) && (driverAge > 24) ) { premium = 650.00 cout << "LOW RISK “ << endl; } else premium = 1200.00 cout << “ HIGH RISK ” << endl; monthlyPayment = premium / 12.0 + 5.00; COSC175-Selection

Example Input Process Output temp Input temp, units newTemp units Convert temperature from fahrenheit to celsius or from celsius to fahrenheit based on C or F Input Process Output temp Input temp, units newTemp units Convert temperature Output newTemp COSC175-Selection

code int main() { float temp; float newTemp; char units; cout << " Enter temperature and C or F" cin >> temp >> units; if (units == 'F') newTemp = (5 * (temp – 32) )/9; cout << temp<< "Degrees F = " <<newTemp<<" Degrees C“; } else newTemp = ((9 * temp)/5) + 32; cout << "Degrees C = " << newTemp << " Degrees F“ << endl; } // end main COSC175-Selection

Exercises: Write the statements that allow you to input a number and prints whether it is positive or negative. Write the statements necessary to input the price of apples and the price of oranges. Then print either "THE APPLES COST MORE" or "THE ORANGES COST MORE. How would you handle the situation where the cost was the same? Write the statements that allow you to input a number and prints whether it is odd or even. COSC175-Selection

Nested selection - Example if (hrsWorked <= 40 ) totPay = hrsWorked * payRate; else { regPay = 40 * payRate; if (hrsWorked <= 60) otPay = (hrsWorked – 40) * (1.5 * payRate); totPay = regPay + otPay; } otPay = 20 * (1.5 * payRate); doubleOtPay = (hrsWorked – 60) * (2 * payRate); grossPay = regPay + otPay + doubleOtPay; COSC175-Selection

Writing a nested if statement as a Multiple-Alternative Decision if (x > 0) cout << “Positive” << endl; else if (x < 0) cout << “Negative” << endl; cout << “Zero” << endl; if (x > 0) cout << “Positive” << endl; else if (x < 0) cout << “Negative” << endl; else cout << “Zero” << endl; COSC175-Selection

Why is italicized code not necessary? cin >> testGrade if (testGrade >= 90) letterGrade = ‘A‘; else if (testGrade >= 80) && testGrade < 90 letterGrade = 'B‘; else if (testGrade >= 70) && testGrade < 80 letterGrade = 'C‘; else if (testGrade >= 60) && testGrade < 70 letterGrade = 'D‘; else if testGrade < 60 letterGrade = 'F‘; Why is italicized code not necessary? COSC175-Selection

cin >> testGrade if (testGrade >= 90) letterGrade = 'A‘; else if (testGrade >= 80 ) letterGrade = 'B‘; else if (testGrade >= 70 ) letterGrade = 'C‘; else if (testGrade >= 60 ) letterGrade = 'D‘; else letterGrade = 'F‘; COSC175-Selection

Nested if Statements if ( Expression1 ) Statement1 else if ( Expression2 ) Statement2 . else if ( ExpressionN ) StatementN else Statement N+1 EXACTLY 1 of these statements will be executed. COSC175-Selection

Multi-way Branching if ( creditsEarned >= 90 ) cout << “SENIOR STATUS “; else if ( creditsEarned >= 60 ) cout << “JUNIOR STATUS “; else if ( creditsEarned >= 30 ) cout << “SOPHOMORE STATUS “; else cout << “FRESHMAN STATUS “; COSC175-Selection

Use nested logic rather than straight thru logic if (age < 16) charge = 7; if ((age >= 16) && (age < 65)) charge = 10; if (age >= 65) charge = 5; if (age < 16 ) charge = 7; else if ((age >= 16) && (age < 65)) charge = 10; else if (age >= 65 ) charge = 5; COSC175-Selection

Testing Selection Control Structures to test a program with branches, use enough data sets so that every branch is executed at least once this is called minimum complete coverage COSC175-Selection

Dangling else else matches nearest unmatched if if (animal == “dog”) if (weight > 40) cost = 15; else cost = 10; if (animal == “dog”) if (weight > 40) cost = 15; else cost = 10; COSC175-Selection

switch Use for multiple tests of one variable switch (selector) { case label1: statement 1 case label2: statement 2 .. case label n: statement n default: statement e } Evaluation: The selector expression is evaluated and compared to each of the case labels. Each labeli is a list of one or more possible constants, separated by commas. Only one statement will be executed. Control is then passed to the first statement following the end of the case. Each statement may be a single or compound statement. COSC175-Selection

Example cin >> menuOpt; switch (menuOpt) { case 1: cout << "Beginners“; break; case 2: cout << "Advanced Beginner“; case 3: cout << "Intermediate“; default: cout << "Invalid Option“ } //END CASE COSC175-Selection

Example cin >> menuOpt; switch (menuOpt) { case 1: case 2: cout << “Buckle my shoe“; break; case 3: case 4: cout << “Shut the door“; case 5: case 6: cout << “Pick up stickse“; default: cout << "Invalid Option“ } //END CASE COSC175-Selection