Chapter 6 PDF

Question 1

What is the flow of control that programmers use to complete jobs with a repetitive pattern called

Answer 1

Looping or iteration

Question 2

What is the while loop designed for

Answer 2

The while loop is designed for repeating a set of operations on data items when we don’t know how many data items there will be

Question 3

How is the end of data items indicated generally

Answer 3

By a special input value called a sentinel value or by reaching the end of file

Question 4

What is is called when you are doing a loop and there is a signal that we are at the end

Answer 4

Receiving the signal is an event and this is called event controlled looping

Question 5

What is special about variables defined within the while loop

Answer 5

Any variable defined within the while loop has block scope and cannot be referenced after the while loop

Question 6

Describe the while loop flow of control

Answer 6

The condition is evaluated. If it is true then we execute the loop. Then the condition is reevaluated.
As long as the condition is true, we execute the loop body. When the condition is false, we skip to the instruction following the loop.

Question 7

Describe the operation of the while loop

Answer 7

If the condition evaluates to true, then the loop body is executed and then the condition is reevaluated. As long as the condition evaluates to true, we continue to repeat the loop body

Question 8

What does the loop body generally do

Answer 8

The loop body usually updates the loop condition - it performs some operation that eventually will cause the loop condition to evaluate to false.

Question 9

What is the loop update used for

Answer 9

The loop update will be an attempt to read the next input value in order to detect the sentinel value or the end of the file

Question 10

What is an iteration

Answer 10

One execution of the loop body

Question 11

What is a loop update

Answer 11

One ar more statements that could cause the loop condition to evaluate to false (and thus end the looping)

Question 12

What is a loop termination condition

Answer 12

The event that causes the loop condition to evaluate to false

Question 13

What is an endless or infinite loop

Answer 13

If the loop condition never values to false, the loop body is executed continuously without end

Question 14

How can we tell if we have an infinite loop

Answer 14

• If the loop body has no output, the computer appears to hang
• If the loop body produces output, the output is repeatedly written without end

Question 15

How can we stop an infinite loop

Answer 15

Abort the program

Question 16

What is a common error associated with a while loop

Answer 16

Avoid putting a semicolon after the condition of a while loop. Adding a semicolon after the condition creates an empty loop body and could result in an endless loop

Question 17

What is a common error with a sentinel controlled while loop

Answer 17

• If you omit the update read it may result in an endless loop
• Omitting the priming read causes the sentinel value to be processed, leading to incorrect results

Question 18

What are the standard patterns and techniques for performing common programming operations (looping)

Answer 18

Accumulation
Counting Items
Finding an average
Finding maximum or minimum values
Animation

Question 19

What is accumulation

Answer 19

Calculating a total of input values

Question 20

What is the approach in accumulation (running count)

Answer 20

We start by initializing a total variable is 0
Each time we read a value, we add the value to the total
When we have no more values to read the total is complete.

Question 21

What is a common error with accumulation

Answer 21

Forgetting to initialize the total variable to 0 before beginning the loop will produce incorrect results

Question 22

What is an easy way to count items (ie: how many people bought a regular ticket, a childs ticket etc)

Answer 22

Using the running count.

Question 23

How would you use the running count

Answer 23

Start by initializing a count variable to 0
Each time you read a value, check whether that value meets the criteria for something we want to count. If so, increase count variable by 1
ETC

Question 24

What is an easy way to calculate an average

Answer 24

Combine accumulation and counting

Question 25

How would you calculate an average by combining accumulation and counting

Answer 25

* *Start by initializing a total variable and a count variable to 0 * *Each time you read an item, add its value to the total variable and increment the count variable. * * When you have no more items to read, calculate the average by dividing the total by the count

Question 26

What is a common error with performing division

Answer 26

forgetting to check whether the denominator is 0 before performing a division

Question 27

What occurs if we declare total and count as integers and then calculate the average

Answer 27

If we declare total and count as integers then average will be calculated using integer division which truncates the remainder

Question 28

How would you get a floating-point average

Answer 28

To get a floating point average, we need to type cast one of the variables (either total or count) to a double or a float to force the division to be performed as a floating point

Question 29

How would you try to get a maximum or minimum value

Answer 29

Use the running maximum or minimum to find it

Question 30

How would you go about getting the maximum

Answer 30

* Read the first item and save its value as the current maximum * Each time we read a new value, we compare it to the current maximum (if it is larger then it becomes new maximum) * When you have no more items to read, current maximum is the max for all values

Question 31

What generally occurs if a user enters a different data type then our request

Answer 31

The scanner next methods generate an InputMismatchException | or the program terminates

Question 32

How can we solve the problem of improper input from our users

Answer 32

Before the scanner reads the line, it can check whether the next input token matches our expected input.

Question 33

What Scanner class method would you use to check if the next input token can be interpreted as the data type specified

Answer 33

The hasNext method of the Scanner class will return true if the next input token can be interpreted as the data type specified

Question 34

What needs to be done if the hasNext method returns the result of false

Answer 34

We need to notify the user that the value typed is not valid and reprompt for new input

Question 35

In a sentinel controlled loop, when would you want to stop the loop

Answer 35

In a sentinel controlled loop we want to stop the loop when the input value is the sentinel.

Question 36

What is a loop termination condition

Answer 36

For a sentinel-controlled loop, we want to stop the loop when the input value is the sentinel.

Question 37

When would you want the loop to keep on executing in a sentinel controlled loop

Answer 37

We would want to keep on executing the loop if the input value is not the sentinel

Question 38

What is a loop continuation condition

Answer 38

When you keep on executing the loop if the input value is not the sentinel

Question 39

What is the first step to constructing a loop condition

Answer 39

1. Define the loop termination condition, that is, define the condition that will make the loop stop executing

Question 40

What is the second step to constructing a loop condition

Answer 40

2. Create the loop continuation condition—the condition that will keep the loop executing—by applying the Logical NOT operator ( ! ) to the loop termination condition.

Question 41

What is the third step to constructing a loop condition

Answer 41

3. Simplify the loop continuation condition by applying DeMorgan's Laws where possible.

Question 42

What are the two DeMorgan's laws

Answer 42

NOT( A AND B ) is equivalent to ( NOT A ) OR ( NOT B ) | NOT( A OR B ) is equivalent to ( NOT A ) AND ( NOT B )

Question 43

What are the three questions to ask yourself when testing for while loops

Answer 43

1. Does the program produce correct results with a set of known input values? 2. Does the program produce correct results if the sentinel value is the first and only input? 3. Does the program deal appropriately with invalid input?

Question 44

What is particular about the do/while loop in relation to the while loop

Answer 44

Unlike the while loop, the condition for the do/while | loop is evaluated at the end of the loop.

Question 45

How many times does the do/while loop execute

Answer 45

A do/while loop executes at least once because the condition is evaluated at the end of the loop.

Question 46

What are some uses of a do/while loop

Answer 46

Validate user input | Ask if the user wants to repeat an operation, such as play a game again

Question 47

What is the do/while flow of control

Answer 47

The do/while loop body is executed, then the condition is checked. If the condition is true, the loop body is repeated. If the condition is false, the loop body is not repeated

Question 48

What occurs if the user input in a do/while flow is not valid

Answer 48

If the user input is not valid, we want to reprompt until the user enters a valid value. Thus, we form the condition so that it is true if the user enters invalid data.

Question 49

Why isn't it advised to use an if statement to validate user input

Answer 49

Do not use an if statement to validate input because it will catch invalid values entered the first time only.

Question 50

What is the benefit to using a do/while loop versus an if statement to validate user input

Answer 50

A do/while loop will continue to prompt the user until the user enters a valid value whereas an if statement will only catch invalid values entered the first time only.

Question 51

When is the for loop ideally used

Answer 51

Ideal when you know the number of iterations to perform before the loop begins

Question 52

What are semicolons used for in the loop header

Answer 52

Semicolons separate terms in the loop header

Question 53

When are curly brackets required with a loop

Answer 53

Curly brackets are required only if more than one statement is in the loop body

Question 54

What is the for loop flow of control

Answer 54

The initialization statement is executed (once only). • The loop condition is evaluated. • If the condition is true, the loop body is executed. • The loop update statement is then executed, and the loop condition is reevaluated.

Question 55

When is a loop control variable convenient

Answer 55

A loop control variable is convenient for counting | iterations of for loops.

Question 56

What is an important way to test for loops

Answer 56

Ensure that the starting and ending values of the loop variable are set correctly.

Question 57

What are nested loops

Answer 57

Nested loops are where the body of one loop contains another loop

Question 58

What is a flag variable used for

Answer 58

A flag variable is used to find something.

Question 59

How would you use a flag variable

Answer 59

– We set the flag to false before starting the for loop that checks for factors. – Inside the for loop, we set the flag to true when we find a factor. – After the for loop terminates, we check the value of the flag. If it is still false, we did not find any factors, and the number is prime.