Pointer variables store memory addresses and can be used to indirectly access other variables. Pointers allow values to be passed by reference into functions rather than by value. Arrays can be accessed using pointers by treating the array name as a pointer to its first element. Dynamic memory allocation with new/delete operators allows pointers to reference variables in heap memory.

1. FUNDAMENTALS OF
C++ PROGRAMMING
6.0 POINTER (PENUDING)

2. 6.1 Understand the concept of pointer

3. Learning Outcome
 At the end of the class, student should be able
to:
 Define pointer and explain its function
 Declare pointer
 Explain new and delete operators

4. What is pointer?
 Pointer is the memory address of a variable.
 Pointer is a variables that are used to store the
addresses of other variables.

5. What is pointer?
Memory Blocks
0x8f8dfff12 0x8f8dfff13 0x8f8dfff14
Address of Memory Blocks

6. Declaring Pointer
 Syntax:
data_type *pointer_name;
Example
double *p;

7. The * and & operators
 * operator
 Reference/dereference operator
 Produce the variable to which it point
 Refer to “value pointed by”
 Pointers are said to "point to"
 Example of usage:
 double *p; // declare pointer to double variable
 void func(int *p) // declare p to be a pointer value
parameter

8. The * and & operators
 & operator
 Address-of operator
 Produce address of variable
 Example:
double *p, v;
p = &v; // p point to address of v

9. Pointer Operator
int *my_pointer;
int my_variable;
my_pointer = &my_variable;
my_pointer =
&my_variable
Pointer Memory location
variables Address
operator

10. How it will look like?
#include<iostream>
using namespace std;
void main()
{
int i;
int *j;
j = &i; //pointer to i
i=4;
cout<<"i = " <<i<<endl;
cout<<"j = " <<j<<endl;
}

11. j = &i; //pointer to address i
i=4;
i 4
j 0012FF60

12. What is the output???
int i;
int *j;
j = &i; //pointer to i
i=4;
cout<<"i = " <<i<<endl;
cout<<"j = " <<*j<<endl;

13. j = &i; //pointer to address i
i=4;
i 4
j 0012FF60
cout<<"j = " <<*j
j 4

14. How it will look like?
#include<iostream>  Output:
using namespace std;
void main()
v1=42
{
int *p1, v1; p1=42
v1 = 0;  Why?
p1 = &v1; //pointer to v1 - As long as p1
*p1 = 42; //value pointed by p1 = 42 contains address to
v1, then both refer
cout<<"v1="<<v1<<endl; to the same
cout<<"p1="<<*p1<<endl; variable
}

15. v1 = 0;
v1 0
p1 = &v1;
&v
p1
1
*p1 = 42; //value pointed by p1 = 42
p1 42
v1 42

16. See difference?
p1 = p2;
p1 8 p1 8
p2 9 p2 9
BEFORE AFTER
*p1 = *p2;
p1 8 p1 9
p2 9 p2 9

17. Pointer Arithmetic
 Pointer can only used two arithmetic operation
addition and subtraction.
int a, int *p; W hat happen is:
p=&a;  pointer move over bytes
p=p+2;  not adding 2 to value of a
 it point to the last 2 x int of the integer
a
Position of pointer p Position of pointer p after
before operation p+2 operation

18. Pointer Arithmetic
 Example: its equivalent to:
#include<iostream>
using namespace std; #include<iostream>
void main() using namespace std;
{ void main()
int arraysize=4; {
int d []={1,2,3,4}; int arraysize=4;
for (int i = 0; i < arraysize; + int d []={1,2,3,4};
+i) for (int i = 0; i < arraysize; ++i)
cout << *(d + i) << " "; cout << d[i] << " ";
} }

19. Pointer & character string
 Use standard function strcmp() uses two pointers to compare
two strings:
strcmp (char *s1, char *s2)
{
while (*s1)
if (*s1 - *s2)
return *s1 - *s2; //if the string are not equal
else
{ s1++;
s2++;
}
return 0;
}

20. new and delete operator
 new operator creates new dynamic variable of
specific type
 It also return a pointer that point to this new
variable
 Eg:
int *n;
n = new int(17); // initialize *n to 17

21. How it will look like?
int *p1, *p2;
p1 ?
p2 ?
p1 = new int;
*p1 = 42;
p1
p2 ?
p1
42
p2 ?

22. p2 = p1; p2 = new int;
p1 ?
p1
42
p2 p2 53
*p2 = 53; *p1 = 88;
p1 p1 88
53
p2 p2 53

23.  delete operator eliminates dynamic variable
 It also returns memory that the dynamic
variable occupied in freestore.
 Eg:
delete p;
// p will be undefined
 Good practice:
 Everytime you delete a pointer variable put it to
NULL to ensure it does not become dangling
pointer!

24. #include<iostream>
using namespace std;
void main()
{
int *p1;
p1 = new int;
*p1 = 10;
cout << "*p1 t = "<< *p1 << endl;
delete p1;
cout << "*p1 t = "<< *p1 << endl;
}

25. In Class Exercise 1
 What is the output?
p1 = p2;
int *p1, *p2;
cout << *p1 << "t"<< *p2 << endl;
p1 = new int;
*p1 = 30;
p2 = new int;
cout << *p1 << "t"<< *p2 << endl;
*p1 = *p2;
*p1 = 10;
cout << *p1 << "t"<< *p2 << endl;
*p2 = 20;
cout << *p1 << "t"<< *p2 << endl;

27. How it will look like?
int *p1, *p2;
p1 ?
p2 ?
p1 = new int;
p2 = new int;
p1
p2
*p1 = 10;
*p2 = 20; p1 10
p2 20

28. p1 = p2;
p1 10
p2 20
*p1 = 30; p1 10
p2 30
*p1 = *p2; p1 30
p2 30

29. In Class Exercise 2
 What is the different between the following
variable?
int *intPtr1, intPtr2;
 Write a declaration for a pointer variable
named my_new_ptr that points to dynamic
variable of type double.

30. 6.2 Illustrate the relationship between
pointer and array

31. Learning Outcome
 At the end of the class, student should be able
to:
 Identify relationship between pointer and array
 Write program using pointer and array

32. Pointer & Array
 Array is a collection of similar type of data
 Variable in an array can store memory address
instead of variable value
 Dynamic array is an array whose size is
determined during run-time.
 It is created using new operator.
 Eg:
double *new_array; //point to 1st index in the
array
new_array = new double[10] //to allocate

33. Pointer in Array: Example 1
#include<iostream>
using namespace std;
void main()
{
int d []={1,2,3,4};
int *p1;
p1=d;
for (int i = 0; i < 4; ++i)
cout << *(p1 + i) << " ";
}

34. Pointer in Array: Example 2
#include <iostream>
using namespace std;
void main()
{
int array_size;
cout << “Enter array size: “;
cin >> array_size;
int* my_dyn_array = new int [array_size];
cout << “Enter ” << array_size << “ number ” << endl;
for (int i = 0; i < array_size; ++i)
cin >> my_dyn_array[i];
}

35. Pointer and Array
 An array declared without specifying its size
can be assume as a pointer to the address of
the first element in the array.
 Eg:
int a[] = {2, 4, 6, 8, 10};
 To iterate to the next element, add operation is
used.

36. Pointer and Array: Example 1
#include <iostream>
using namespace std;
int main()
{
char susun[] = "Selamat belajar";
char * pt_str;
pt_str = susun; / point to first element
/
cout << "Turutan sblm perubahan " << susun;
cout << "
nSebelum perubahan, kandungan susun[5] : " <<susun[5];
* (pt_str+5) = 'C'; /change the 6th element
/
cout << "
nSelepas perubahan, kandungan susun[5] : " <<susun[5];
cout << "
nTurutan slps perubahan" << susun;
return 0;
}

38. Pointer and Array: Example 2
#include <iostream>
using namespace std;
int main()
{
int senarai[] = {1,2,3,4,5};
int * point;
point=senarai; / point to first element
/
cout << "
nTurutan sblm perubahan " << senarai[0] << " " << senarai[1];
cout << " " << senarai[2] << " " << senarai[3] << " " << senarai[4];
cout << "
nSebelum perubahan, kandungan senarai[2] : " <<senarai[2];
* (point+2)= 7; / change the 3rd element
/
cout << "
nSelepas perubahan, kandungan senarai[2] : " <<senarai[2];
cout << "
nTurutan slps perubahan " << senarai[0] << " " << senarai[1];
cout << " " << senarai[2] << " " << senarai[3] << " " << senarai[4];
cout << endl;
return 0;
}

40. In Class Exercise 3
 Write a declaration for pointer variable named
char_ptr that will be used to point to a dynamic
array of type char.
 What is the output for the following code?
int c[3] = {2, 3, 4};
int arraysize = 3, * p;
p = c;
for (int i = 0; i < arraysize; ++i)
cout << c[i] << “ “;
for (i = 0; i < arraysize; ++i)
cout << * (p + i) << “ “;

41.  Declaration
char * char_ptr; //point to 1st index in the array
char_ptr = new char[6];
 What is the output for the following code?

42. 6.3 Illustrate the relationship between
pointer and function

43. Learning Outcome
 At the end of the class, student should be able
to:
 Identify relationship between pointer and function
 Use pointer as function argument
 Write program using pointer and function

44. Pointer & Functions
 2 types of function calls:
 Call by value
 Call by reference
 Pointer can be used as parameters in both
function

45. Pointers & Function
#include <iostream>
using namespace std; void Change (int *a, int *b, int *c)
{
void Change (int *, int *, int *); *a = 100;
*b = 200;
*c = 300;
void main() }
{
int x=50, y=60, z=70;
cout << "nx = " << x << "ny = " << y received address
<< "nz = " << z << "nn";
Change (&x, &y, &z);
cout << "nx = " << x << "ny = " << y
<< "nz = " << z << "nn"; change value in
} variable that is point
by a,b,c

47. How it will look like?
Change(&x, &y, &z);
void Change(int *a, int *b, int *c)
{ &x
50
*a = 100; x (100) 1001
*a
*b = 200; 1001 *a
&y
*c = 300; 60
y (200) 1002
} 1002
*b
*b
70 &z
z (300) 1003
*c
1003 *c

48. Pointers & Function
#include <iostream> void Change (int &a, int &b, int &c)
using namespace std; {
a = 100;
b = 200;
void Change (int &, int &, int &);
c = 300;
}
void main() received address
{
int x=50, y=60, z=70;
cout << "nx = " << x << "ny = " << y
<< "nz = " << z << "nn"; change value refered by
Change (x, y, z); a,b,c
cout << "nx = " << x << "ny = " << y
<< "nz = " << z << "nn";
}

50. Summary
 Pointer is a memory address
 Pointer variable provides way to indirectly
name variable by naming the address of
variable in memory
 new and delete operator can be use to
allocate and free the memory after pointer is
used
 Dynamic array is array whose sized is
determined during runtime
 Function can have pointer variable as its
parameter variables.