In C++, an object is considered fully initialised when execution enters the body of the constructor.
“i wanted to know why const must be
intialized in constructor initializer
list rather than in it’s body ?.”
What you are missing is that initialisation happens in the initialisation list, and assignment happens in the body of the constructor. The steps in logic:
1) A const object can only be initialised.
2) An object has all of its members initialised in the initialisation list. Even if you do not explicitly initialise them there, the compiler will happily do so for you 🙂
3) Therefore, putting 1) and 2) together, a member which is const can only ever have a value assigned to it at initialisation, which happens during the initialisation list.