Pointers

What is null pointer? What will be the output of following program? Explain. Write a program to calculate the length of string without using string handling function.

#include <stdio.h>
int main() {
  if(!NULL)
    printf("C programming is easy");
  else
    printf("C programming is not easy");
  return 0;
}

Compare call by value and call by reference with example. Write the output of the program shown below. Given memory addresses: a: 6422296, ptr1: 6422292, ptr2: 6422280 (a initially contains 10; pointer value boxes are blank in the printed diagram).

#include <stdio.h>
int main()
{
  int a=10,*ptr1,**ptr2;
  ptr1=&a;
  ptr2=&ptr1;
  printf("%d\t %d \n",a,&a);
  printf("%d\t %d \n",&ptr1,ptr1);
  printf("%d\t %d \n",*ptr1,*ptr2);
  **ptr2=20;
  printf("%d",a);
  return 0;
}

Write the output of the following. The printed memory diagram gives a=10 at address 65510, b at address 65550 and c at address 65580; b and c value boxes are blank. What do you mean by Generic pointer, Null pointer and File pointer?

int a=10,*b,**c;
b=&a;
c=&b;
printf("%d\t%d\n",b,*c);
printf("%d\t%d\n",c,**c);
printf("%d\t%d",*b+5,&c+2);