Example of malloc() in C

Malloc () is used to allocate user-defined bytes on the heap.

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

int main() {
  //Allocating memory dynamically on the heap
  //for an integer, which returns an int* pointer
  int* a = (int*) malloc (sizeof(int));
  if (a != NULL)
      printf("Allocated memory for an integer\n");
  else
      printf("malloc() failed");
  int x = 100;
  //We can update the value to this location, since
  //we have allocated memory for the pointer
  *a = x;
  printf("a points to %d\n", *a);

  int* b;
  //Will give a segmentation fault, since
  //*b is not allocated any memory
  *b = x;
  printf("b points to %d\n", *b);
  
  //Free memory from the heap
  free(a);
  return 0;
}

This example uses' malloc() 'to allocate memory for the integer position pointed to by a.
Since memory has been allocated, this value can be updated.
However, another pointer b that did not allocate memory anywhere could not update its value, and a segmentation error occurred due to an attempt to access a NULL location.

output:

Allocated memory for an integer
a points to 100
[1]    14671 segmentation fault (core dumped)  ./a.out