what is its o/p and why?

Code:

---

void main()
{
  int *p,*q;
  p=(int*)1000;
  q=(int*)2000;
  printf("%d",(q-p));
}
 
    why it outputs 500.anyone know the reason??help me

---

A much safer version which doesn't rely on undefined pointer behaviour.

Code:

---

#include <stdio.h>
int main ( ) { /* Verily, main doest always return an int */
    int arr[100];
    int *p = &arr[10];
    int *q = &arr[40];
    printf("&#37;d\n",(q-p));
    return 0;
}

---

Then try this one

Code:

---

#include <stdio.h>
int main ( ) { /* Verily, main doest always return an int */
    double arr[100];
    double *p = &arr[10];
    double *q = &arr[40];
    printf("%d\n",(q-p));
    return 0;
}

---

Notice anything?

On your box, int * is 2 bytes. So two addresses which are 1000 bytes apart are 500 int *'s apart.

See the FAQ regarding void main()... On my 32bit system (an int is 4 bytes) the result is 250, so the two addresses are 1000 bytes appart, or 4 * 250 bytes.