When do u use #include <iomanip> ?

you ought to when t use it and when its not necessary…basically now i’m asking what’s it for

Whenever you need to manipulate your output.So pertaining to things like setprecision, ios::showpoint, among other suggestions.

You utilize it when you need to do a number of I/O mind games.See
http://www.fredosaurus.com/notes-cpp/io/omanipulators.html document.