whenever a value is assigned to any pointer variable that is not working under windows 7 (32 bit) environment. Program containing such a code are getting execution error.
Actually I was trying to concatenate two strings without using any library functions.
Example:

```
   int main()
   {
       char *s1 = "Hello";
       char *s2 = "World";
       char *p;
       p = s1;

       while(*s1 != '\0')
          s1++;

       while(*s2 != '\0')
       {
           *s1 = *s2;  // this line creating problem
           s1++;
           s2++;
       }
       *s1 = '\0';  // this line also creating problem

       while(*p != '\0')
       {
           cout<<*p;
           p++;
       }

       return 0;

    }

```