const char *x;
   char const *a = x;
   char *b;
   char *c = "ABCDEF";

   b = (char*)malloc(sizeof(char)*120);

   memcpy(b, "Anything", 9);

   // Illegal
   memcpy(c, b, 5);  // c points to a "constant" memory area
   
   // Legal
   x = b;   // x (the pointer) can be modified
   // Illegal
   memcpy(x, "1234", 5);  // Although the memory is not constant, x is a pointer to constant memory, so this should not be allowed

   // Illegal
   a = x;    // a cannot point to any other place (a cannot be modified)
   
   // Legal
   free(b);
   b = strdup(c);
   // Now you can use a COPY of the data that is constant in a non-constant memory area

// and so on...