C++ Tutorial - More On Classes - Member Initializers

Question

I'm a little confused with the examples on two of the pages here.
This is the example given on the Second Page, which looks like it belongs in the Header file.

class MyClass {
public:
MyClass(int a, int b)
: regVar(a), constVar(b)
{
}
private:
int regVar;
const int constVar;
};

-----------------------------------------------------------------

Then on the Third Page, the example given is:

MyClass.h

class MyClass {
public:
MyClass(int a, int b);
private:
int regVar;
const int constVar;
};

-----------------------------------------------------------------

MyClass.cpp

MyClass::MyClass(int a, int b)
: regVar(a), constVar(b)
{
cout << regVar << endl;
cout << constVar << endl;
}

Why has the " :regVar(a), constVar(b)" seemingly moved?
In case anyone needs a link to the full pages: https://www.sololearn.com/Play/CPlusPlus/

Answer 1

answer is student, regVar and <<.

Answer 2

1. The constructor definition is in the declaration.

2. The class only has functions declarations, so you can write their definitions separatedly.

In a declarations you could write only the id and parameters' type, in a definition you need to specify paramaters' name ( and constant definition )