Why we need to use "using namespace std;" in CodeBlocks ?

Why we need to use "using namespace std;" in CodeBlocks ?

Hello there
I have just started learning C++. At my college we use Turbo C++ but I don't like that compiler because I think its outdated. For this reason I use and like Codeblocks. Because its more advanced then Turbo. However, when I was writing program at CodeBlocks I was getting some error and then I noticed in the default main.cpp file that the compiler added below code in hello world default program...

Then I have added that in my program and it works like a charm. When I was writing program with Turbo I didn't need to add that line. Then why we need to add that into CodeBlocks ? I just want to know the reason of using that. Does anybody know why we need to use that ??