Decision Structure - 2 ISYS 350

Complex Condition with Logical Operators The logical AND operator (&&) and the logical OR operator (||) allow you to connect multiple Boolean expressions to create a compound expression The logical NOT operator (!) reverses the truth of a Boolean expression Operator Meaning Description && AND Both subexpression must be true for the compound expression to be true || OR One or both subexpression must be true for the compound expression to be true ! NOT It negates (reverses) the value to its opposite one. Expression Meaning x >y && a < b Is x greater than y AND is a less than b? x == y || x == z Is x equal to y OR is x equal to z? ! (x > y) Is the expression x > y NOT true?

Logical Operators: &&, ||, ! Cond1 Cond2 Cond1 && Cond2 T T T F F T F F || Cond1 Cond2 Cond1 || Cond2 ! Cond ! Cond T F

Examples Write a complex condition for: 12 <= Age <= 65 Use a complex condition to describe age not between 12 and 65. X <= 15 is equivalent to: X<15 AND X =15? (T/F)

More Complex Conditions University admission rules: Applicants will be admitted if meet one of the following rules: 1. Income >= 100,000 2. GPA > 2.5 AND SAT > 900 An applicant’s Income is 150,000, GPA is 2.9 and SAT is 800. Admitted? Income >= 100,000 OR GPA > 2.5 AND SAT >900 How to evaluate this complex condition? AND has higher priority

Is a CIS student with GPA = 2.0 qualified? Scholarship: Business students with GPA at least 3.2 and major in Accounting or CIS qualified to apply: 1. GPA >= 3.2 2. Major in Accounting OR CIS Is a CIS student with GPA = 2.0 qualified? GPA >= 3.2 AND Major = “Acct” OR Major = “CIS” Is this complex condition correct? Parenthesis, ( )

NOT Set 1: Young: Age < 30 Set 2: Rich: Income >= 100,000 Young

Young: Age<30 Rich: Income >100000 private void button1_Click(object sender, EventArgs e) { double Age, Income; Age = double.Parse(textBox1.Text); Income = double.Parse(textBox2.Text); if (Age < 30 && Income > 100000) MessageBox.Show("You are young and rich"); else MessageBox.Show("You are not young or not rich"); }

Data Entered in Textbox1 Must Be between 10 and 30 private void textBox1_Validating(object sender, CancelEventArgs e) { double enteredData; enteredData = double.Parse(textBox1.Text); if (enteredData<10 || enteredData>30) MessageBox.Show("Pls enter a number between 10 and 30"); e.Cancel=true; }

Boolean (bool) Variables and Flags You can store the values true or false in bool variables, which are commonly used as flags A flag is a variable that signals when some condition exists in the program False – indicates the condition does not exist True – indicates the condition exists Boolean good; // bool good; if (mydate.Year == 2011) { good = true; } else { good = false; } MessageBox.Show(good.ToString());

Using Boolean Variables and && private void button1_Click(object sender, EventArgs e) { bool Young=false, Rich=false; double Age, Income; Age = double.Parse(textBox1.Text); Income = double.Parse(textBox2.Text); if (Age < 30) Young = true; if (Income > 100000) Rich = true; if (Young && Rich) MessageBox.Show("You are young and rich"); else MessageBox.Show("You are not young OR not rich"); }

Using Boolean Variables and || private void button1_Click(object sender, EventArgs e) { bool Young=false, Rich=false; double Age, Income; Age = double.Parse(textBox1.Text); Income = double.Parse(textBox2.Text); if (Age < 30) Young = true; if (Income > 100000) Rich = true; if (Young || Rich) MessageBox.Show("You are young OR rich"); else MessageBox.Show("You are not young and not rich"); }

The if-else-if Statement Rules to determine letter grade Avg>=90 A 80<=Avg<90 B 70<=Avg<80 C 60<=Avg<70 D Avg<60 F

Compare the two programs if (grade < 60) { MessageBox.Show("F"); } else if (grade < 70) MessageBox.Show("D"); else if (grade < 80) MessageBox.Show("C"); else if (grade < 90) MessageBox.Show("B"); else MessageBox.Show("A"); if (grade < 60) { MessageBox.Show("F"); } if (grade >=60 && grade < 70) MessageBox.Show("D"); if (grade >= 70 && grade < 80) MessageBox.Show("C"); if (grade >= 80 && grade < 90) MessageBox.Show("B"); if (grade >=90 ) MessageBox.Show("A");