what actually happens in call by default value process?

Answer 1

No, defaulted parameters and references are two completely different things.
Defaulted parameters are just giving a parameter a standard value, if not given in the call to the function.
"Call by reference" is a way of passing a parameter. Defaulted parameters can be "call by reference" but they can also be "call by value".
So you see, they are independent of each other. I give you that both things have to do with passing parameters to a function but that's where the similarity ends.
Anyways, your question was about what happens, when a function with default parameters is called. As I assume that you mean the technical details and not just conceptually, I can't tell. I don't know this part of the standard well enough and there is a multitude of options of how a compiler could generate code for it.

Answer 2

"Call by value" or "default parameters "?

Answer 3

ok

Answer 4

"Ok" is not an answer to my question. Which of the both is it? Or is it a third thing you mean?

Answer 5

see call by default value is another process and it is allmost same as call by reference.

Answer 6

thanks a lot 👍

Answer 7

No problem. 🙂