Question

When answering these questions, please write them in standard English. I asked this question earlier and the answers were all correct, but I had a very hard time understanding what was trying to be said, if you know what I mean.

Chapter 9 (Pointers) – Review Questions

Short Answer

1.     What does the indirection operator do?

2.     Look at the following code.

int x = 7;

int *ptr = &x;

What will be displayed if you send the expression *ptr to cout? What happens if you send the expression ptr to cout?

3.     So far you have learned three different uses for the * operator. What are they?

4.     What math operations are allowed on pointers?

5.     Assuming ptr is a pointer to an int, what happens when you add 4 to ptr?

6.     Look at the following array definition.

int numbers[] = {2, 4, 6, 8, 10};

What will the following statement display?

cout << *(numbers + 3) << endl;

7.     What is the purpose of the new operator?

8.     What is the purpose of the delete operator?

9.     Under what circumstances can you successfully return a pointer from a function?

10. What is the difference between a pointer to a constant and a constant pointer?

11. What are two advantages of declaring a pointer parameter as a constant pointer?

Fill-in-the-Blank

12. Each byte of memory is assigned a unique ___________.

13. The _________ operator can be used to determine a variable’s address.

14. ____________variables are designed to hold addresses.

15. The ___________ operator can be used to work with the variable a pointer points to.

16. Array names can be used as _________, and vice versa.

17. Creating variables while a program is running is called ____________.

18. The ____________ operator is used to dynamically allocate memory.

19. A pointer that contains the address 0 is called a(n) ________ pointer.

20. When a program is finished with a chunk of dynamically allocated memory, it should free it with the __________ operator.

21. You should only use pointers with delete that were previously used with __________.

Algorithm Workbench

22. Look at the following code:

double value = 29.7;

double *ptr = &value;

Write a cout statement that uses the ptr variable to display the contents of the value variable.

23. Look at the following array definition:

int set[10];

Write a statement using pointer notation that stores the value 99 in set[7]

24. Write a code that dynamically allocates an array of 20 integers, then uses a loop to allow the user to enter values for each element of the array.

25. Assume tempNumbers is a pointer that points to a dynamically allocated array. Write code that releases the memory used by the array.

26. Look at the following function definition:

void getNumber(int &n)

{

     cout << “Enter a number: “;

     cin >> n;

}

In this function, the parameter n is a reference variable. Rewrite the function so n is a pointer.

27. Write the definition of ptr, a pointer to a constant int.

28. Write the definition of ptr, a constant pointer to an int.

True or False

29. Each byte of memory is assigned a unique address. T F

30. The * operator is used to get the address of a variable. T F

31. Pointer variables are designed to hold addresses. T F

32. The & symbol is called the indirection operator. T F

33. The & operator dereferences a pointer. T F

34. When the indirection operator is used with a pointer variable, you are actually working with the value the pointer is pointing to. T F

35. Array names cannot be dereferenced with the indirection operator. T F

36. When you add a value to a pointer, you are actually adding that number times the size of the data type referenced by the pointer. T F

37. The address operator is not needed to assign an array’s address to a pointer. T F

38. You can change the address that an array name points to. T F

39. Any mathematical operation, including multiplication and division, may be performed on a pointer. T F

40. Pointers may be compared using the relational operators. T F

41. When used as function parameters, reference variables are much easier to work with than pointers. T F

42. The new operator dynamically allocates memory. T F

43. A pointer variable that has not been initialized is called a null pointer. T F

44. The address 0 is generally considered unusable. T F

45. In using a pointer with the delete operator, it is not necessary for the pointer to have been previously used with the new operator. T F

Find the Error

Each of the following definitions and program segments has errors. Locate as many as you can.

46. int ptr* = nullptr;

47. int x, *ptr = nullptr;

&x = ptr;

48. int x, *ptr = nullptr;

*ptr = &x;

49. int x, *ptr = nullptr;

ptr = &x;

ptr = 100; //Store 100 in x

cout << x << endl;

50. int numbers[] = {10, 20, 30, 40, 50};

cout << “The third element in the array is ”;

cout << *numbers + 3 << endl;

51. int values[20], *iptr = nullptr;

iptr = values;

iptr *= 2;

52. float level;

int fptr = &level;

53. int *iptr = &ivalue;

int ivalue;

54. void doubleVal(int val)

{

*val *= 2;

}

55. int *pint = nullptr;

new pint;

56. int *pint = nullptr;

pint = new int;

if (pint == nullptr)

*pint = 100;

else

cout << “Memory allocation error\n”;

57. int *pint = nullptr;

pint = new int[100]; //Allocate memory

.

.

Code that process the array.

.

.

delete pint; // Free memory

58. int *getNum()

{

int wholeNum;

cout << “Enter a number: “;

cin >> wholeNum;

return &wholeNum;

}

59. const int arr[] = {1, 2, 3};

int *ptr = arr;

60. void doSomething(int * const ptr)

{

int localArray[] = {1, 2, 3};

ptr = localArray;

       }

Answer 1

Hey that is a one big list of question.But anyway these are the answers of some of them.
1. The indirection operator de-references the pointer; allows you to work with the value the pointer is pointing to.

2. When a * is used with ptr while cout, it means value at. So value at ptr is 7. But when only ptr is used with cout the address store at ptr i.e of 7 will be printed.

3. Uses of *
For multiplication: int a = 2*3 = 6

For pointer definition: int *a;

For indirection: *x= 5, stores 5 at location pointed

4. Addition of integer, Subtraction of integer and Subtracting two pointers of the same type are only 3 operations allowed on pointers.

5. After multiplying 4 by the no. of bytes of an int it adds it to the memory address.

6. It is same as numbers[3] which is 8.

7. New operator are used for Dynamic Memory Allocation to set aside a chunk of memory for a specific data type.

8. Delete operator is used to de-allocate the memory of an object.

9. A pointer should only be returned from a function if it is a pointer to an object that was passed into the function.

10. Constant pointer can never change its address they are pointing to on the other hand pointer to a constant means the one which can not change the value it is pointing to.

I hope these helps.