What is the difference??

[arun srinivaas]

int const & refToConst = i; // OK
int & const constRef = i; // Error the "const" is redundant

what is the difference between the two ..?

[Narue]

The first is a reference to const int, the object being referenced is const. The second is a const reference to int, the reference itself is const. However, a const reference is nonsensical because references are permanently bound to a single object on definition. To have a const reference implies that you could rebind the reference to another object, which is not allowed.

[pseudorandom21]

Such is also true to pointers. const char * constantData; char * const constantPointer; const char * const constantAll;