Part 2 - References, Pointers, Arrays and Strings

Question 1

In C++ a variable of class type is associated with ________

Answer 1

a block of memory

Question 2

If variables s1 and s2 are of type Student, the statement

s2 = s1;

will do what>

Answer 2

Make a copy of s1 and put it in the memory block associated with s2

Question 3

Why would a loop like

for (i = 0; i<10; i++) {

Student s = a[i];

s. addMark(…);
s. updateAverage();

}

Not be suitable in C++?

What should be done instead?

Answer 3

s would make a copy of a[i];

Instead:

Student &s = a[i];

Question 4

When declaring a reference variable what must be done?

i.e. what is not allowed?

Answer 4

Give it a value.

Student &s; would not be allowed

Question 5

What is the default way of passing parameters in C++?

Answer 5

Call by value

Value is copied into local scope variable

Question 6

What will

void swap(int &x, int &y) {

int temp = y;

y = x;

x = temp

}

do?

Answer 6

Swap the two integers passed in - references mean it is swapped outside the method also

Question 7

When passing objects in C++ what type of calling is usually used? Why?

Answer 7

Call by reference

Because otherwise it would be pointlessly making a copy of the object

Question 8

How should the function

void displayMarks(Student &s);

be defined if we want to guarantee s will not be modified?

Answer 8

void displayMarks (const Student &s);

Question 9

When passing an array to a function what is actually passed?

Answer 9

The address of the start of the array

Question 10

What will a return statement return if the return type is an object?

Answer 10

A copy of the object

Question 11

Why should a reference to a local variable not be returned from a function?

What should be done instead?

Answer 11

Once control leaves the function the local variable will cease to exist

Instead return a copy

Question 12

What do self referential classes need to use for the attributes of the same type?

Answer 12

Pointers

Question 13

If a pointer p points to an object, how can the object it points to be accessed?

Answer 13

*p

Question 14

Write a function to swap two integers using pointers

Show how it would be called

Answer 14

void swap(int* i1, int* i2) {

int t = *i1;

*i1 = *i2;

*i2 = t;

}

swap(&a, &b);

Question 15

a->b is equal to what?

Answer 15

(*a).b

Question 16

References are implicitly ___________ where as pointers must use the ________ operator

Answer 16

dereferenced

*

Question 17

Write a function that takes a function pointer (to a function that takes and returns an int), an array and a length

Answer 17

void applyAll(int (*func)(int), int arr[], int len) {

for (int i = 0; i < len; i++) {

(*func)(arr[i]);

}

}

Question 18

All data items on the stack must have a __________ size

Answer 18

fixed

Question 19

When creating data items whose sizes are not known until runtime the

a) stack
b) heap

must be used

Answer 19

b) heap

Question 20

If an array has been dynamically created like so:

int *anArray = new int[10];

How must it be deleted?

Answer 20

delete [] anArray;