The purpose of writing using namespace std; is that
The program will know to look in the std library to find the object. Namespace std contains all the classes, objects and functions of the standard C++ library.
JAZAKALLAH alam.so after writing using name space std we do not have to write other directives like <math>,<string> etc.?am i right?
The real point is not what anyone chooses to use.
It is what they choose to recommend.
The two may not be the same.