Why the code attached below isn't working?

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

 int main(void)
 {
    int a=10 ;
    int *p;
    p = &a;
    *(p+1) = 20;
    printf("The value at (p+1) is %d\n",*(p+1));

    return 0;
  }

I’m trying to do some pointer arithmetic and trying to implement the code. I’m trying to assign value 20 to next address in the memory using *(p+1) and print it using the printf statement, but my code isn’t producing any output. Why is it so?

>Solution :

Look at it this way, *(p + 1) is the same as having p[1] this means you are looking for the data in a[1] but a is not an array, a[1] does not exist in your program, we don’t really know what’s in the memory location you are trying to access, that is why your program suffers from undefined behavior.