Question

In the following program,

int main()
   {

     char a[] = "azmruf";
     char *ptr = a;

     ptr += 5;  

     //Now ptr points at 'f'

     printf("%c", --*ptr--); //e got printed. Bcos of post increment now ptr in u.
     printf("%c", *ptr);     // so 'u' got printed now.

     // Next --*--ptr becomes --*(--ptr), 
     // ptr is moved to r, then --r i.e q is printed, but pointer should 
     // be in 'r'   
     printf("%c", --*--ptr);

     //Im here getting 'q' only instead of 'r'. There is no 'q' in my string.(??!!!)
     printf("%c", *ptr);        

     return 0;
   }

How i’m getting ‘q’ in last printf()??

Answer 1

The decrement operator has a very important side effect. Namely, that it decreases the value stored by one. Your original array had an ‘r’ in it, but that has been replaced by a ‘q’. After your code runs, the whole array looks like:

"azmque"

The stored values actually changed, so when you reference the fourth element of the array a second time (aka *ptr or a[3]), the value at that location is ‘q’.