31 Input/output library [input.output]

31.5 Iostreams base classes [iostreams.base]

31.5.5 ios_base manipulators [std.ios.manip] basefield manipulators [basefield.manip]

Each function specified in this subclause is a designated addressable function ([namespace.std]).
ios_base& dec(ios_base& str);
Effects: Calls str.setf(ios_base​::​dec, ios_base​::​basefield).
Returns: str.271
ios_base& hex(ios_base& str);
Effects: Calls str.setf(ios_base​::​hex, ios_base​::​basefield).
Returns: str.
ios_base& oct(ios_base& str);
Effects: Calls str.setf(ios_base​::​oct, ios_base​::​basefield).
Returns: str.
The function signature dec(ios_base&) can be called by the function signature basic_ostream& stream​::​operator<<(ios_base& (*)(ios_base&)) to permit expressions of the form cout << dec to change the format flags stored in cout.