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Explain dynamic memory allocation in C with an example
Problem
Find the sum of n numbers entered by user using dynamically allocated memory using C programming.
Solution
The Dynamic memory allocation enables the C programmers to allocate memory at runtime.
The different functions that we used to allocate memory dynamically at run time are −
- malloc () − allocates a block of memory in bytes at runtime.
- calloc () − allocating continuous blocks of memory at run time.
- realloc () − used for reduce (or) extend the allocated memory.
- free () − deallocates previously allocated memory space.
Following C program is to display the elements and calculate sum of n numbers.
Using dynamic memory allocation functions, we are trying to reduce the wastage of memory.
Example
#include<stdio.h>
#include<stdlib.h>
void main(){
//Declaring variables and pointers,sum//
int numofe,i,sum=0;
int *p;
//Reading number of elements from user//
printf("Enter the number of elements : ");
scanf("%d",&numofe);
//Calling malloc() function//
p=(int *)malloc(numofe*sizeof(int));
/*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);
}
//Printing elements//
printf("Enter the elements :
");
for(i=0;i<numofe;i++){
scanf("%d",p+i);
sum=sum+*(p+i);
}
printf("
The sum of elements is %d",sum);
free(p);//Erase first 2 memory locations//
printf("
Displaying the cleared out memory location :
");
for(i=0;i<numofe;i++){
printf("%d
",p[i]);//Garbage values will be displayed//
}
}Output
Enter the number of elements : 5 Enter the elements : 23 34 12 34 56 The sum of elements is 159 Displaying the cleared out memory location : 12522624 0 12517712 0 56
Updated on: 09-Mar-2021
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