Use of namespace

[yuktikutty]

i dont know 'what is the use of namespace in C.why we declare it as "using namespace"!

[willakawill]

i dont know 'what is the use of namespace in C.why we declare it as "using namespace"!

Hi
Each library could, potentially, use the same function names and your program would fail. Imagine that 2 different library functions were called getkey() or if you made your own library and came up with the name getkey() for a function thinking that it was unique. There would then be 2 different functions both called getkey() and the compiler would not know which one to use.

To make sure there is no confusion, a name is put in front of the function name. In your own library you could use yuktikutty. Then you could distinguish from the other library functions like this:

mychar = yuktikutty::getkey();

or

mychar = std::getkey();

so there is no confusion for the compiler.
If you know that you will definitely not be introducing new functions with the same name as the libraries you are using you can put this at the top of your file,

using namespace std;

so you don't have to type the std:: part any more.

mychar = getkey();

[murcielagossi]

Or if you don't want to use the entire library you could use something like

using std::cout; or
using std::cin;

or you could omit the "using" directive and plainly state std::cout. However this leaves out all other elements such as endl; and so forth ,because they were not cited. Like willakawill's said its better to take advantage of the entire library.