Dynamic Memory Allocation

Dynamic Memory Allocation

The dynamic memory allocation is done using an operator new. The syntax of dynamic memory allocation using new is

Name_of_the_variable data type;

For example:

int *p;

p=new int;

We can allocate the memory for more than one element. For instance if we want to allocate memory of size in for 5 elements we can declare.

int *p;

p=new int[5];

In this case, the system dynamically assigns space for five elements of type int and returns a pointer to the first element of the sequence, which is assigned to p. Therefore, now, p points to a valid block of memory with space for five elements of type int.

The program given below allocates the memory for any number of elements and the memory for those many number of elements get deleted at the end of the program.

C++ Program

#include<iostream>

using namespace std;

void main ()

{

     int i,n;

     int *p:

     clrscr();

     cout << "How many numbers would you like to type? ";

     cin >> i;

     p = new int[i];//dynamic memory allocation

 if (p = = 0)

     cout << "Error: memory could not be allocated":

else

{

     for (n=0; n<i; n++)

     {

          cout << "Enter The Number: ";

          cin>> p[n];

     }

cout << "You have entered: ";

for (n=0; n<i; n++)

cout<<"" <<p[n];

delete[] p://dynamic memory deallocation

}

getch();

}

Output

How many numbers would you like to type? 7

Enter The Number: 10

Enter The Number: 20

Enter The Number: 30

Enter The Number: 40

Enter The Number: 50

Enter The Number: 60

Enter The Number: 70

You have entered: 10 20 30 40 50 60 70

The use of dynamic memory allocation avoids the wastage of memory. Because the programmer can allocate the memory as per his need using new operator and when that memory block is not needed it is deallocated.

Review Question

1. Explain the operators used for dynamic memory allocation with examples.