Just a general question;

This is a discussion on Just a general question; within the C++ Programming forums, part of the General Programming Boards category; Could somebody please explain to me the differences between "#include"-ing header files, and the "using namespace" code and what each ...

  1. #1
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    Just a general question;

    Could somebody please explain to me the differences between "#include"-ing header files, and the "using namespace" code and what each does? Thanks :]

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    Programming Wraith GReaper's Avatar
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    "#include" takes the whole text of a file and places it in this file.
    "using namespace" is a completely different thing;
    For C++ to avoid name collisions between same function names, there is an option that we declare a function not global, but part of a namespace.
    Example:
    Code:
    #include <iostream>
    
    int main()
    {
         std::cout << "Hello World!";
         std::cin.get();
          
         return 0;
    }
    "using namespace" just makes all functions under this namespace global

    Code:
    #include <iostream>
    
    using namespace std;
    
    int main()
    {
         cout << "Hello World!";
         cin.get();
          
         return 0;
    }
    Devoted my life to programming...

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    So in your second example, int main and anything below it would be considered a global function?

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    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by fthmdg View Post
    So in your second example, int main and anything below it would be considered a global function?
    No. It puts the namespace "std" into the global namespace (so that std::cout is now in the global namespace and can now be called just cout, e.g.).

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    Programming Wraith GReaper's Avatar
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    Exactly
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    so in a weird way namespaces are like groups of functions?
    and using a namespace just allows you to call any of those functions from within that cpp file?

    and header files are basically just a list of variables, prototypes, and other stuff like that

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    Programming Wraith GReaper's Avatar
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    My bad, when i say "under the namespace" i mean "declared and/or defined inside the namespace". I should've though that you'd take it literally...
    Devoted my life to programming...

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    Well yeah, I figured that much. Thanks for the help :]

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