Chapter 4 : Looping

Question 1

How to add items to ListBox?

Answer 1

ListBoxName.Items.Add(Item);

• Item is the value to be added to the items property

namesListBox.Items.Add(“Chris”);
namesListBox.Items.Add(“Alicia”);
namesListBox.Items.Add(10);
namesListBox.Items.Add(20);
namesListBox.Items.Add(17.5);

Question 2

How to clear items to ListBox?

Answer 2

1. ListBoxName.Items.Clear();

Question 3

How to count items stored in ListBox?

Answer 3

1. ListBoxName.Items.Count();

Question 4

What is for loop specially designed for?

Answer 4

1. Situations requiring a counter variable to control the number of times that a loop iterates

Question 5

List out 3 actions that are required for the for loop

Answer 5

1. Initialization
   
   • One-time expression that defines the initial value of the counter
2. Test
   
   • A boolean expression to be tested
3. Update
   
   • Increase or decrease the value of the counter

Question 6

What is the format for for loop?

Answer 6

for ( initializationExpress; textExpression; updateExpression ){}

• For loop is a pretest loop

Question 7

List out examples for using for loop

Answer 7

for (int count = 0; count <=100; count += 10) → count = count + 10
{
MessageBox.Show(count.ToString());
}

for (int count = 10; count >=0; count–)
{
MessageBox.Show(count.ToString());
}

Question 9

What does the while loop causes?

Answer 9

1. A statement or set of statements to repeat as long as a Boolean expression is true

Question 10

List out 2 parts for while loop

Answer 10

1. A boolean expression that is tested for a true or false value
2. A statement or set of statements that is repeated a long as the Boolean expression is true

Question 11

List out format for while loop

Answer 11

counter declaration
while ( BooleanExpression )
{
Statements;
counter increment / decrement
}

• First line is called the while clause
  Statements inside the curly braces are the body of the loop
  When a while loop executes, the Boolean expression is tested, if true, the statements are executed

Question 12

What is the term used each time the loop executes its statements again and again?

Answer 12

1. Iteration

• While loop is a pretest loop

Question 13

What is a dead loop?

Answer 13

1. A loop that will never gets executed

Question 14

What is the issue caused by a loop become a dead loop?

Answer 14

1. Logical error in the boolean expression

// count variable is always greater than 5
int count = 5;
while (count > 5)
{
MessageBox.Show(“Hello”);
count=count+1;
}

Question 15

List out 3 ways to increase 1of the value

Answer 15

1. count = count + 1;
2. count++;
3. count += 1;

Question 16

List out 3 ways to decrease 1of the value

Answer 16

1. count = count - 1;
2. count–;
3. count -= 1;

Question 17

What is Postfix Mode?

Answer 17

1. Means to place the ++ and – operators after their operands

count++

int a, b;
a = 50;
MessageBox.Show(a++); // 50
b = a;
MessageBox.Show(a); // 51
MessageBox.Show(b); //51

Question 18

What is Prefix Mode?

Answer 18

1. Means to place the ++ and – before their operands

–count

int a, b;
a = 50;
MessageBox.Show(++a); // 51
b = a;
MessageBox.Show(a); //51
MessageBox.Show(b); //51

Question 19

Is do-while loop a posttest loop?

Answer 19

1. Yes

• One or more statements are executed before a Boolean expression is tested

Question 20

What is the format for do-while loop?

Answer 20

do
{
statement(s);
} while (BooleanExpression);