Program 67 - CSU1128 - CSE 2026 - Shoolini University

Program to demonstrate the dynamic memory allocation techniques in C by the values entered by the user

Explanation

The program demonstrates dynamic memory allocation techniques in C using the values entered by the user. It covers memory allocation using malloc, calloc, and realloc functions.

Header

The code begins with including the standard input-output and standard library header files using #include <stdio.h> and #include <stdlib.h>.

Variable Declaration

The main() function is defined, and several variables are declared:

  • int d, m, j, o;: Variables to hold the size values entered by the user for different memory allocation functions.
  • void *e;: Pointer to hold the allocated memory address.

Program Description

The program prints a description message for the user to understand its functionality.

Malloc Allocation

The program allocates memory using malloc:

  • printf("Enter the size of memory to allocate using malloc: ");: Prompts the user to enter the size of memory to allocate using malloc.
  • scanf("%d", &d);: Reads the size entered by the user and stores it in d.
  • e = malloc(d);: Allocates memory of size d bytes using malloc.
  • if (e == NULL): Checks if memory allocation failed.
    • printf("Error allocating memory\n");: Prints an error message if memory allocation failed.
    • return 1;: Exits the program with an error code.

Calloc Allocation

The program allocates memory using calloc:

  • printf("Enter the number of elements and size of each element to allocate using calloc: ");: Prompts the user to enter the number of elements and size of each element to allocate using calloc.
  • scanf("%d %d", &m, &j);: Reads the values entered by the user and stores them in m and j.
  • e = calloc(m, j);: Allocates memory for an array of m elements, each of size j bytes, using calloc.
  • if (e == NULL): Checks if memory allocation failed.
    • printf("Error allocating memory\n");: Prints an error message if memory allocation failed.
    • return 1;: Exits the program with an error code.

Realloc Allocation

The program reallocates memory using realloc:

  • printf("Enter the new size to allocate using realloc: ");: Prompts the user to enter the new size to allocate using realloc.
  • scanf("%d", &o);: Reads the new size entered by the user and stores it in o.
  • e = realloc(e, o);: Reallocates memory to the new size o bytes using realloc.
  • if (e == NULL): Checks if memory allocation failed.
    • printf("Error allocating memory\n");: Prints an error message if memory allocation failed.
    • return 1;: Exits the program with an error code.

Free Memory

The program frees the allocated memory:

  • free(e);: Frees the memory allocated by malloc, calloc, or realloc.

Program End

The program ends with return 0; to indicate successful execution.

Code

                    
/*
 * -----------------------------------------------------------
 * Logic Building with Computer Programming (CSU1128)
 * Instructor: Dr. Pankaj Vaidya | Author: Divya Mohan
 * 
 * This code is a part of the educational initiative by dmj.one
 * with aim of empowering and inspiring learners in the field of
 * Computer Science and Engineering through the respective courses.
 * 
 * (c) 2022, Divya Mohan for dmj.one. All rights reserved.
 * -----------------------------------------------------------
 */

#include <stdio.h>
#include <stdlib.h>

int main()
{
    printf("\n\n Program to demonstrate the dynamic memory allocation techniques in C by the values entered by the user. \n\n");

    // Declare variables
    int d, m, j, o, n;
    void *e;

    // Get user input for malloc
    printf("Enter the size of memory to allocate using malloc: ");
    scanf("%d", &d);

    // Allocate memory using malloc
    e = malloc(d);
    if (e == NULL)
    {
        printf("Error allocating memory\n");
        return 1;
    }

    // Get user input for calloc
    printf("Enter the number of elements and size of each element to allocate using calloc: ");
    scanf("%d %d", &m, &j);

    // Allocate memory using calloc
    e = calloc(m, j);
    if (e == NULL)
    {
        printf("Error allocating memory\n");
        return 1;
    }

    // Get user input for realloc
    printf("Enter the new size to allocate using realloc: ");
    scanf("%d", &o);

    // Reallocate memory using realloc
    e = realloc(e, o);
    if (e == NULL)
    {
        printf("Error allocating memory\n");
        return 1;
    }

    // Free the allocated memory
    free(e);

    return 0;
}

Output

Program to demonstrate the dynamic memory allocation techniques in C by the values entered by the user.

Enter the size of memory to allocate using malloc: 5
Enter the number of elements and size of each element to allocate using calloc: 12 43
Enter the new size to allocate using realloc: 23