c - Case insensitive comparison of constant strings -

I am trying to use this function to compare two strings, in an insensitive case.

  Int strcasecmp (const char * x1, const char * x2);   
 My copy is correct, however, the sensitive section is giving me some trouble because const is a static, thus only to read, they fail:  < Pre>  * x1 = (tolower (* x1)); // toopper will suffice enough, I just chose Tiller * x2 = (tolower (* x2)); // same code here   
 should be  const  in both characters, otherwise I think this will work ... So my question: keeping the capitalization undiscovered One way to do this is by using the  four  --string  const ?   
 
 
 You can use a floating variable variable:  
  Char c1 = tolower (* x1); Four C2 = Toller (* x2); If (C1 == C2) ...