What do you mean by Dynamic memory allocation in C programming?

Dynamic Memory Allocation

• Allocation of memory at the time of execution (run time) is known as dynamic memory allocation.

• The functions calloc() and malloc() support allocating of dynamic memory.

• Dynamic allocation of memory space is done by using these functions when value is returned by functions and assigned to pointer variables.

• In this case, variables get allocated only if your program unit gets active.

• It uses the data structure called heap for implementing dynamic allocation.

• There is memory reusability and memory can be freed when not required.

• It is more efficient.

• In this memory allocation scheme, execution is slower than static memory allocation.

• Here memory can be released at any time during the program.

Example

Following program computes the sum of even numbers and odd numbers in a set of elements using dynamic memory allocation functions −

 Live Demo

#include<stdio.h>
#include<stdlib.h>
void main(){
   //Declaring variables, pointers//
   int i,n;
   int *p;
   int even=0,odd=0;
   //Declaring base address p using malloc//
   p=(int *)malloc(n*sizeof(int));
   //Reading number of elements//
   printf("Enter the number of elements : ");
   scanf("%d",&n);
   /*Printing O/p -
   We have to use if statement because we have to check if memory
   has been successfully allocated/reserved or not*/
   if (p==NULL){
      printf("Memory not available");
      exit(0);
   }
   //Storing elements into location using for loop//
   printf("The elements are : 
");
   for(i=0;i<n;i++){
      scanf("%d",p+i);
   }
   for(i=0;i<n;i++){
      if(*(p+i)%2==0){
         even=even+*(p+i);
      }
      else{
         odd=odd+*(p+i);
      }
   }
   printf("The sum of even numbers is : %d
",even);
   printf("The sum of odd numbers is : %d
",odd);
}

Output

Enter the number of elements : 4
The elements are :
35
24
46
12
The sum of even numbers is : 82
The sum of odd numbers is : 35