title: "module, import, export"

ms.date: "07/15/2019"

f1_keywords: ["module_cpp", "import_cpp", "export_cpp"]

helpviewer_keywords: ["modules [C++]", "modules [C++], import", "modules [C++], export"]

Use the **module** statement at the beginning of a module implemetation file to specify that the file contents belong to the named module.

module ModuleA;

Use the **export module** statement for the module's primary interface file, which must have extension **.ixx**:

export module ModuleA;

In an interface file, use the **export** modifier on names that are intended to be part of the public interface:

export module ModuleA;

namespace Bar

{

export int f();

export std::string s();

}

When the **export** modifier is applied to a namespace name, all names in the namespace are exported. The **export** keyword may not appear in a module implementation file.

Use the **import** statement to make a module's names visible in your program. The import statement must appear after the module statement and after any #include directives, but before any declarations in the file.

module ModuleA;

#include "custom-lib.h"

import std.core;

import std.regex;

import ModuleB;

template <class T>

class Baz

{...};