What is the purpose of the “extern” keyword in C#?

In C#, the extern keyword is used to declare an external managed function or method. It tells the compiler that the implementation of that function or method is not in the current assembly, but in external unmanaged code or other managed code. It is commonly used for interacting with other languages, such as interoperating with C or C++ code. When using the extern keyword, the signature of the external function or method needs to be provided, and the specific implementation is specified in the program through the DllImport attribute or other means.