Is it mandatory to use namespace std ?

Question

Isn't enough that we are using header file. it contains all features though. why we using namespace then?

Answer 1

no it is not mandatory. some even discourage its usage.
There has been much discussion here on this topic. I will link one such post below for you. If you would like to view more you can use the search function with the keyword namespace or namespaces
https://www.sololearn.com/discuss/294730/?ref=app

Answer 2

thanks a lot. I get it.