Is there modes in cpp as in c (r w a)?

Answer 1

I think the mod is implicit in type of file. When you choose ofstream you mean that you choose w-mod and if you define ifstream you choose r-mod

Answer 2

Check this out: http://www.cplusplus.com/reference/fstream/fstream/open/

Answer 3

second parameter of open () gives multiple modes. ios::in, ios::out etc.