Deck 10: Pointers and Dynamic Arrays

Question 1

Given the definitions,
int *p1,*p2;
p1 = new int;
p2 = new int;
You are to compare and contrast the two assignments.
a)p1 = p2;
b)*p1 = *p2

Answer 1

a)Makes p1 point to the same place in memory to which p2 points.Orphans memory p1 did point to.
b)Makes data where p1 points the same as the data where p2 points.

Question 2

In deep copy,pointers are followed and data and the pointer structure are duplicated.

Answer 2

True

Question 3

When declaring several pointer variables,there must be one pointer declarator * for each pointer variable.

Answer 3

True

Question 4

Dangling pointers present no problem in C++

Question 5

The default copy constructor and default operator = provide deep copy.

Question 6

Give three uses for the * operator.Name and describe each use.

Question 7

A function can return an array.

Question 8

A copy constructor has the same name as the class (let's call it A)and has a parameter that

A)Is call-by value of an A object
B)Is call-by-reference of another class
C)Is call-by-reference of an A class object
D)Is call-by-name of an object named ~A.
E)None of these

Question 9

Give the output from this code fragment:
int *p1,*p2;
p1 = new int;
p2 = new int;
*p1 = 10;
*p2 = 20;
cout << *p1 << " " << *p2 << endl;
*p1 = *p2;
cout << *p1 << " " << *p2 << endl;
*p1 = 30;
cout << *p1 << " " << *p2 << endl;

Question 10

Pointer variables are just memory addresses and can be assigned to one another without regard to type.

Question 11

If a class is named MyClass,what must the destructor be named?

A)Erase
B)MyClass
C)Any name the programmer wishes except the name of the class
D)~MyClass
E)None of the above.

Question 12

Dynamic variables or dynamically allocated variables in C++ are created and destroyed according to the program's needs.

Question 13

A pointer is an address,an address is an integer,but a pointer is not an integer.

Question 14

An array name is a constant pointer to array base type.

Question 15

There should eventually be a call to the operator delete on a pointer that
points to the memory allocated by each call to new.

Question 16

Given the declarations below,write a code fragment that allocates a nameless variable for pointer p1 to point to.
int *p1,*p2;

Question 17

Suppose we have the following definitions and assignments:
double *p,v;
p = &v;// p gets the address of v
What is the effect of this assignment?
*p = 99.99

Question 18

A pointer is a variable that holds the address of some other location in memory.

Question 19

You can get a pointer value to initialize a pointer variable from an object of an appropriate type with the "address-of" operator,&.

Question 20

One can use the & operator to extract the value that a pointer points to.

Question 21

Give the sequence of steps for creating and using a dynamic array.

Question 22

Why did C++11 introduce the nullptr constant when we already have NULL?

Question 23

Write a type definition for a type called NumberPtr that will be the type for pointer variables that hold pointers to dynamic variables of type double.Also,write a declaration for a pointer variable called myPoint,which is of type NumberPtr.

Question 24

It is an error to call the delete operator on a pointer a second time.Consider what happens if there is memory allocated on the free store for a class,a destructor,and initializing constructors have been defined,but no copy constructor was defined.Now suppose a function is called that has call-by-value parameters.Why does the program either die in the middle or give a segmentation fault?

Question 25

Describe the action of the new operator.What does the new operator return? What are the indications of error?

Question 26

Tell about the freestore (also known as heap).What is put there? How is this done? How does a program access the freestore? What happens to memory that has been allocated but is no longer needed?

Question 27

Here is the first line of the copy constructor for PFArrayD.The identifier PFArrayD is the name of the class,but in the header it is used three times with different meaning each time.Give the meaning for each use:
PFArrayD::PFArrayD( const PFArrayD& pfaObject)

Question 28

Your program creates a dynamically allocated array as follows:
int *entry;
entry = new int[10];
so that the pointer variable entry is pointing to the dynamically allocated array.Write code to fill this array with 10 numbers typed in at the keyboard.

Question 29

Write a type definition for pointer variables that will point to dynamically allocated arrays whose base type is char.The name of the type will be CharArray.