there is only default value for last parameter of all arguments?does the previous parameter have any default value?

Answer 1

By default arguments haven't default values. You can put default values to some arguments of a function:
someFunction (int a, int b, int c=7){..}
Or to all arguments:
someFunction (int a=1, int b=5, int c=7){..}
Alway starting with the last ones.