If the parameters are being passed by reference then the modifications done will be reflected
in the original parameters also.And If they being passed by value then the copy of the variable is passed to the function and the scope of those passed value will be within the function itself.Once out from the function they are gone.

So in your case if the parameters are being passed as value then withing the function the value will be 2 and 4.But once the control return to the main then in the main it will be 1 and 3.

if the parameters are being passed as reference then the value will be 2 and 4 in the main also.