class

class foo {
    int x;
  public:
    int get_x();
    void set_x(int new_x);
};

class foo; // elaborated type specifier -> forward declaration
class bar {
  public:
    bar(foo& f);
};
void baz();
class baz; // another elaborated type specifer; another forward declaration
           // note: the class has the same name as the function void baz()
class foo {
    bar b;
    friend class baz; // elaborated type specifier refers to the class,
                      // not the function of the same name
  public:
    foo();
};

template <class T>
const T& min(const T& x, const T& y) {
    return b < a ? b : a;
}

template <template <class T> class U>
//                           ^^^^^ "class" used in this sense here;
//                                 U is a template template parameter
void f() {
    U<int>::do_it();
    U<double>::do_it();
}

template <class T>
class foo {
};

foo<class bar> x; // <- bar does not have to have previously appeared.

enum class Format {
    TEXT,
    PDF,
    OTHER,
};
Format f = F::TEXT;