1. Decision Structure - 2
ISYS 350

2. 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?

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

4. 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)

5. 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 Admitted?
Income >= 100,000 OR GPA > 2.5 AND SAT >900
How to evaluate this complex condition?
AND has higher priority

6. 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, ( )

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

8. 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 > )
MessageBox.Show("You are young and rich");
else
MessageBox.Show("You are not young or not rich"); }

9. 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; }

10. 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());

11. 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 > ) Rich = true;
if (Young && Rich)
MessageBox.Show("You are young and rich");
else
MessageBox.Show("You are not young OR not rich"); }

12. 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 > ) Rich = true;
if (Young || Rich)
MessageBox.Show("You are young OR rich");
else
MessageBox.Show("You are not young and not rich"); }

13. 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

14. 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");

15. Tax Rate Schedule Rules to determine tax rate:
Taxable Income < = no tax
3000 < taxable income <= % tax
10000<Taxable income <= % tax
Taxable income> %
double taxableIncome, taxRate, tax;
taxableIncome = double.Parse(textBox1.Text);
if (taxableIncome <= 3000) {
taxRate = 0; }
else if (taxableIncome<=10000)
taxRate= .05;
else if (taxableIncome <= 50000)
taxRate = .15;
else
taxRate = .25;
tax = taxableIncome * taxRate;
textBox2.Text = tax.ToString("C");