Difference between prototype declaration and forward declaration?

Question

So I have this code:

class xx
{
    int getnum(); //Is this a forward declaration or a prototype declaration and why?
};

int xx::getnum()
{
    return 1+3;
         


        

Answer 1

A forward declaration is a declaration of an identifier (denoting an entity such as a type, a variable, a constant, or a function) for which the programmer has not yet given a complete definition.

On the other hand a prototype refers to a function not an identifier.

Hope the following clear things out for you!

int getnum(); // Function prototype. You have not yet implemented the body of getnum() function, thus its a forward delcaration. 
class RandomClass; // Forward declaration of RandomClass. You have not yet implemented this class but you need it for the rest of your code.

class xx{
    RandomClass *foo; // Our need of having a member like that, made us make a forward declaration of the class RandomClass, above class xx
    void BarFunction(); // Function Prototype!
};

int getnum(){ //This is the simply the body of your prototype above. Has nothing to do with the classes
    return 1+3;
}

void BarFUnction(){
     cout << "foo-bar\n" ;
}