Pointer in C language

#include <stdio.h>

int main(void) {
  
  //pointer variable of type int
  int *ptr = NULL;
  
  printf("Value stored in ptr: %ld\n", ptr);
  
  return 0;
}

Value stored in ptr: 0

Initialize pointer variables with addresses

#include <stdio.h>

int main(void) {
  
  //num variable
  int num = 10;
  
  //pointer variable
  int *ptr;
  
  //assign address of num variable to ptr pointer variable
  ptr = &num;
  
  //print the value stored in num using the num variable
  printf("Value stored in num: %d\n", num);
  
  //print address of num stored in ptr variable
  printf("Address of num variable: %ld\n", ptr);
  
  //print address of ptr variable
  printf("Address of ptr variable: %ld\n", &ptr);
  
  //print the value stored in num using ptr variable
  printf("Value stored in num using ptr variable: %d\n", *ptr);
  
  return 0;
}

Value stored in num: 10
Address of num variable: 140732844468280
Address of ptr variable: 140732844468272
Value stored in num using ptr variable: 10