There is a reason for this error, although some compliers might just generate a warning. As Andy stated, you are setting a non-constant pointer to a const. There is such a thing as a pointer to a const (there is also a const pointer, which is different).

If you were to declare your pointer as follows, you shouldn't have an error:

const char *mycharptr;
const char mystr = 'A';

mycharptr = &mystr;

This is an example of a pointer to a constant, where the value being pointed to can't be modified. A const pointer on the other hand, can't change where it is pointing to, but the value at the location is pointing to can be changed.