Namespace - Namespaces in Programming Languages

Namespaces in Programming Languages

For many programming languages, namespace is a context for their identifiers. In an operating system, an example of namespace is a directory. Each name in a directory uniquely identifies one file or subdirectory, but one file may have the same name multiple times.

As a rule, names in a namespace cannot have more than one meaning; that is, different meanings cannot share the same name in the same namespace. A namespace is also called a context, because the same name in different namespaces can have different meanings, each one appropriate for its namespace.

Following are other characteristics of namespaces:

• Names in the namespace can represent objects as well as concepts, be the namespace a natural or ethnic language, a constructed language, the technical terminology of a profession, a dialect, a sociolect, or an artificial language (e.g., a programming language).
• In the Java programming language, identifiers that appear in namespaces have a short (local) name and a unique long "qualified" name for use outside the namespace.
• Some compilers (for languages such as C++) combine namespaces and names for internal use in the compiler in a process called name mangling.

Below is an example of a namespace in C++:

namespace Box1{ int boxSide = 4; } namespace Box2{ int boxSide = 12; } int main { int boxSide = 42; cout << Box1::boxSide << endl; //output 4 cout << Box2::boxSide << endl; //output 12 cout << boxSide << endl; // output 42 return 0; }