1

Data Structure & Algorithm

Pointer & Class

2

Pointer & Class

Pointer can be used to store the address of other variables with types of int, char, float, and double

These types of data also known as primitive data types as it already exist/defined in C/C++

It’s possible to have a pointer that point to new data type (ADT) such as class defined by the user

An introduction to class & pointer should has been explained briefly in the Abstract Data Type topic before

3

Class Definition

Applying pointer to class required a new class to be defined first

Below is an example of simple class definition for student

class student { private: char name[10]; int mark;

public: void set_info(char [], int); void print_info();};

4

Class Implementation

Next is the implementation for the student class

void student::set_info(char n[], int m) { strcpy(name, n); mark = m;

// reformat name int offset = 10 - strlen(name);

if (offset > 0) { strncat(name, " ", offset); }}

void student::print_info() { cout << name << " - " << mark;}

5

Class Instance

We might use the class as follows:

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

6

Class Instance

We might use the class as follows:

s1 is an instance of class (student)

Like other primitive data types an instance of class also have address allocated in the memory

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

7

Class Instance Address

Just follow the syntax: &var_name to get the address of s1

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

cout << "Address of s1 = " << &s1 << endl;

8

Class Instance & Pointer

How to store the address of s1 into other variable (pointer)?

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

cout << "Address of s1 = " << &s1 << endl;

9

Class Instance & Pointer

Follow the rule that for pointer declare as T *P, P can only store address referred by other variables with type of T

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

cout << "Address of s1 = " << &s1 << endl;

10

Class Instance & Pointer

For the example below T is the new data type which is the class (student) and P can be any possible valid variable name let say p

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

cout << "Address of s1 = " << &s1 << endl;

11

Class Instance & Pointer

For the example below T is the new data type which is the class (student) and P can be any possible valid variable name let say p

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

cout << "Address of s1 = " << &s1 << endl;

student *p = &s1;

12

Class Instance & Pointer

Add more few lines of code to get more information about s1 and p

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

cout << "Address of s1 = " << &s1 << endl;

student *p = &s1;

13

Class Instance & Pointer

Add more few lines of code to get more information about s1 and p

student s1;

s1.set_info("KHUZAIMAH", 46);s1.print_info(); cout << endl;

cout << "Address of s1 = " << &s1 << endl;

student *p = &s1;

cout << “ Value of p = " << p << endl; cout << "Address of p = " << &p << endl;

14

Class Instance & Pointer

Below is the possible output for the program until the slide #13:

KHUZAIMAH - 46Address of s1 = 0xbffdb920 Value of p = 0xbffdb920 Address of p = 0xbffdb91c

15

Class Instance & Pointer

Below is the possible output for the program until the slide #13:

s1 is an instance of class (student) with its member variables name set to “KHUZAIMAH” and mark set to 46

KHUZAIMAH - 46Address of s1 = 0xbffdb920 Value of p = 0xbffdb920 Address of p = 0xbffdb91c

16

Class Instance & Pointer

Below is the possible output for the program until the slide #13:

s1 is an instance of class (student) with its member variables name set to “KHUZAIMAH” and mark set to 46

p is a pointer with type of student and currently has the address of s1 as its value (it’s pointing to s1)

KHUZAIMAH - 46Address of s1 = 0xbffdb920 Value of p = 0xbffdb920 Address of p = 0xbffdb91c

17

Class Instance & Pointer

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Below is the table of memory representing the current state for s1 and p

s1&s1

*p p&p

18

Class Instance & Pointer

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

In the example code given there is a line s1.print_info(); which calling one of the method define in the class (student)

s1&s1

*p p&p

19

Class Instance & Pointer

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

In the example code given there is a line s1.print_info(); which calling one of the method define in the class (student)

s1.print_info()&s1

*p p&p

20

Class Instance & Pointer

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

In the example code given there is a line s1.print_info(); which calling one of the method define in the class (student)

s1.print_info()&s1

*p p&p

21

Access Class Member Function via Pointer

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Is it possible to call print_info() method via *p?

s1.print_info()&s1

*p p&p

22

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Will *p.print_info(); do the same as s1.print_info();?

s1.print_info()&s1

p&p *p

Access Class Member Function via Pointer

23

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

It will not do the same and give an error at compilation time, the correct one is: (*p).print_info();

s1.print_info()&s1

p&p *p

Access Class Member Function via Pointer

24

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

It will not do the same and give an error at compilation time, the correct one is: (*p).print_info();

s1.print_info()&s1

p&p (*p).print_info()

Access Class Member Function via Pointer

25

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

It will not do the same and give an error at compilation time, the correct one is: (*p).print_info();

s1.print_info()&s1

p&p (*p).print_info()

Access Class Member Function via Pointer

26

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

There is another technique that more intuitive by changing it from (*p).print_info(); to p->print_info();

s1.print_info()&s1

p&p (*p).print_info()

Access Class Member Function via Pointer

27

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

There is another technique that more intuitive by changing it from (*p).print_info(); to p->print_info();

s1.print_info()&s1

p&p p->print_info()

Access Class Member Function via Pointer

28

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Access Class Member Function via Pointer

29

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

30

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

31

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

32

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name KHUZAIMAHmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

33

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name ADAMmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

34

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name ADAMmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

35

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name ADAMmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

36

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name ADAMmark 46set_info(n, m)print_info()

Access Class Member Function via Pointer

37

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name ADAMmark 51set_info(n, m)print_info()

Access Class Member Function via Pointer

38

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name ADAMmark 51set_info(n, m)print_info()

Access Class Member Function via Pointer

39

Changing member data variables of s1 via p can be done as follows:

p->set_info(“ADAM”, 51);

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

. . . . . . . . . . . .

name ADAMmark 51set_info(n, m)print_info()

Access Class Member Function via Pointer

40

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

name ADAMmark 51set_info(n, m)print_info()

The simplified version of visual context for s1 and p

p->print_info()

Instance & Pointer Simplified Visual Context

41

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

name ADAMmark 51set_info(n, m)print_info()

The simplified version of visual context for s1 and p

p->print_info()

Instance & Pointer Simplified Visual Context

42

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

name ADAMmark 51set_info(n, m)print_info()

The simplified version of visual context for s1 and p

p->print_info()

s1ADAM

51

Instance & Pointer Simplified Visual Context

43

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

name ADAMmark 51set_info(n, m)print_info()

The simplified version of visual context for s1 and p

p->print_info()

s1ADAM

51

Instance & Pointer Simplified Visual Context

44

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

name ADAMmark 51set_info(n, m)print_info()

The simplified version of visual context for s1 and p

p->print_info()

s1ADAM

51

p.

Instance & Pointer Simplified Visual Context

45

Variable Name Type Address Value

. . . . . . . . . . . .

s1 student 0xbffdb920

p student * 0xbffdb91c 0xbffdb920

name ADAMmark 51set_info(n, m)print_info()

The simplified version of visual context for s1 and p

p->print_info()

s1ADAM

51

p.

Instance & Pointer Simplified Visual Context

46

Pointer & Class Instances Exercise

student *p, *p2, *temp;

47

Pointer & Class Instances Exercise

student *p, *p2, *temp;

p

.

p2

.

temp

.

48

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

p

.

p2

.

temp

.

49

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

p

.

p2

.

temp

.

s1

name?

mark?

50

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p

.

p2

.

temp

.

s1

name?

mark?

51

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p

.

p2

.

temp

.

s1

ARRIF

86

52

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1; p

.

p2

.

temp

.

s1

ARRIF

86

53

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1; p

.

p2

.

temp

.

s1

ARRIF

86

54

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p

.

p2

.

temp

.

s1

ARRIF

86

55

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p

.

p2

.

temp

.

s1

ARRIF

86

???

name?

mark?

56

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p

.

p2

.

temp

.

s1

ARRIF

86

???

name?

mark?

57

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

p

.

p2

.

temp

.

s1

ARRIF

86

???

name?

mark?

58

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

59

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

Write the next lines of code so the p and p2 will look like below.

60

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

61

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

62

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

63

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p = p2;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

64

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p = p2;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

65

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p = p2;p2 = temp;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

66

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p = p2;p2 = temp;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

67

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p = p2;p2 = temp;

temp = NULL;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer:

68

Pointer & Class Instances Exercise

student *p, *p2, *temp;student s1;

s1.set_info(“ARRIF", 86);

p = &s1;p2 = new student;

p2->set_info(“FIRDAUS”, 58);

temp = p;

p = p2;p2 = temp;

temp = NULL;

p

.

p2

.

temp

.

s1

ARRIF

86

???

FIRDAUS

58

The answer: