Explain the use of malloc function in C programming.

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 Explain the use of malloc function in C programming?

C malloc() method

“malloc” or “memory allocation” method in C is used to dynamically allocate a single large block of memory with the specified size. It returns a pointer of type void which can be cast into a pointer of any form. It initializes each block with a default garbage value.

Syntax:

ptr = (cast-type*) malloc(byte-size)

For Example:

ptr = (int*) malloc(100 * sizeof(int));

Since the size of int is 4 bytes, this statement will allocate 400 bytes of memory. And, the pointer ptr holds the address of the first byte in the allocated memory.

Description

The C library function void *malloc(size_t size) allocates the requested memory and returns a pointer to it.

Declaration

Following is the declaration for malloc() function.

void *malloc(size_t size)

Return Value

This function returns a pointer to the allocated memory, or NULL if the request fails

If space is insufficient, allocation fails and returns a NULL pointer.

Example:

#include <stdio.h>
#include <stdlib.h>
  
int main()
{
  
    // This pointer will hold the
    // base address of the block created
    int* ptr;
    int n, i;
  
    // Get the number of elements for the array
    n = 5;
    printf("Enter number of elements: %d\n", n);
  
    // Dynamically allocate memory using malloc()
    ptr = (int*)malloc(n * sizeof(int));
  
    // Check if the memory has been successfully
    // allocated by malloc or not
    if (ptr == NULL) {
        printf("Memory not allocated.\n");
        exit(0);
    }

    else {
  
        // Memory has been successfully allocated
        printf("Memory successfully allocated using malloc.\n");
  
        // Get the elements of the array
        for (i = 0; i < n; ++i) {
            ptr[i] = i + 1;
        }
  
        // Print the elements of the array
        printf("The elements of the array are: ");
        for (i = 0; i < n; ++i) {
            printf("%d, ", ptr[i]);
        }
    }
  
    return 0;
}

Output:
Enter number of elements: 5
Memory successfully allocated using malloc.
The elements of the array are: 1, 2, 3, 4, 5

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