1. 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?
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2. Relational Operators < less than <= less than or equal to
> greater than
>= greater than or equal to
== equals
!= not equal to
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3. Examples 10 > 2 'a' < 'c' Why is this true? x != y
temp > humidity
num == 35
initial != ‘Q’
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4. Logicals: AND && OR || NOT !
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5. 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;
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6. “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))

7. Selection/Decision Test – true or false
One operation performed if true
One operation performed if false
Keywords
if, else
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8. if Syntax if ( Expression ) statement NOTE: statement can be
a single statement,
a null statement, or
a compound statement.
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9. 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
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10. 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"
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11. 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.
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12. 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
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13. int carDoors, driverAge;
float premium, monthlyPayment;
if ( (carDoors == 4 ) && (driverAge > 24) ) {
premium =
cout << "LOW RISK “ << endl; }
else
premium =
cout << “ HIGH RISK ” << endl;
monthlyPayment = premium / ;
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14. 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
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15. 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
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16. 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.
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17. 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;
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18. 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;
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19. 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?
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20. 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‘;
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21. 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.
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22. 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 “;
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23. 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;
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24. 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
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25. 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;
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26. 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.
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27. 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
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28. 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
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