Example 1: malloc() and free()
This program calculates the sum of n numbers entered by the user. To perform this task,
memory is dynamically allocated using malloc(), and memory is freed using free()
function.
#include <stdio.h>
#include <stdlib.h>
int main()
{
int n, i, *ptr, sum = 0;
printf("Enter number of elements: ");
scanf("%d", &n);
ptr = (int*) malloc(n * sizeof(int));
if(ptr == NULL)
{
printf("Error! memory not allocated.");
exit(0);
}
printf("Enter elements: ");
for(i = 0; i < n; ++i)
{
scanf("%d", ptr + i);
sum += *(ptr + i);
}
printf("Sum = %d", sum);
free(ptr);
return 0;
}
Example: Find Largest Element Using Dynamic Memory
Allocation - calloc()
#include <stdio.h>
#include <stdlib.h>
int main()
{
int i, num;
float *data;
printf("Enter total number of elements(1 to 100): ");
scanf("%d", &num);
// Allocates the memory for 'num' elements.
data = (float*) calloc(num, sizeof(float));
if(data == NULL)
{
printf("Error!!! memory not allocated.");
exit(0);
}
printf("\n");
// Stores the number entered by the user.
for(i = 0; i < num; ++i)
{
printf("Enter Number %d: ", i + 1);
scanf("%f", data + i);
}
// Loop to store largest number at address data
for(i = 1; i < num; ++i)
{
// Change < to > if you want to find the smallest number
if(*data < *(data + i))
*data = *(data + i);
}
/*C program to read and print the student details
using structure and Dynamic Memory Allocation.*/
#include <stdio.h>
#include <stdlib.h>
/*structure declaration*/
struct student
{
char name[30];
int roll;
float perc;
};
int main()
{
struct student *pstd;
/*Allocate memory dynamically*/
pstd=(struct student*)malloc(1*sizeof(struct
student));
if(pstd==NULL)
{
printf("Insufficient Memory, Exiting... \n");
return 0;
}
/*read and print details*/
printf("Enter name: ");
gets(pstd->name);
printf("Enter roll number: ");
scanf("%d",&pstd->roll);
printf("Enter percentage: ");
scanf("%f",&pstd->perc);
printf("\nEntered details are:\n");
printf("Name: %s, Roll Number: %d, Percentage:
%.2f\n",pstd->name,pstd->roll,pstd->perc);
return 0;
}
#include <stdio.h>
#include <stdlib.h>
int main()
int n;
char *text;
printf("Enter limit of the text: ");
scanf("%d",&n);
/*allocate memory dynamically*/
text=(char*)calloc(n,sizeof(char));
printf("Enter text: ");
//scanf(" "); /*clear input buffer*/
gets(text);
printf("Inputted text is: %s\n",text);
/*Free Memory*/
free(text);
return 0;
/*C program to read and print the N student
details using structure and Dynamic Memory Allocation.*/
#include <stdio.h>
#include <stdlib.h>
/*structure declaration*/
struct student
{
char name[30];
int roll;
float perc;
};
int main()
{
struct student *pstd;
int n,i;
printf("Enter total number of elements: ");
scanf("%d",&n);
/*Allocate memory dynamically for n objetcs*/
pstd=(struct student*)malloc(n*sizeof(struct
student));
if(pstd==NULL)
{
printf("Insufficient Memory, Exiting... \n");
return 0;
}
/*read and print details*/
for(i=0; i<n; i++)
{
printf("\nEnter detail of student [%3d]:\n",i+1);
printf("Enter name: ");
scanf(" "); /*clear input buffer*/
gets((pstd+i)->name);
printf("Enter roll number: ");
scanf("%d",&(pstd+i)->roll);
printf("Enter percentage: ");
scanf("%f",&(pstd+i)->perc);
}
printf("\nEntered details are:\n");
for(i=0; i<n; i++)
{
printf("%30s \t %5d \t %.2f\n",(pstd+i)-
>name,(pstd+i)->roll,(pstd+i)->perc);
}
return 0;
}
