Dynamic-link libraries (DLLs) are a key feature of Microsoft Windows. As the name suggests, a DLL is a library of procedures that applications can link to and use at run time rather than link to statically at compile time. This means that DLLs can be updated independently of the application, and many applications can share a single DLL. Microsoft Windows is itself composed of several DLLs that contain the procedures all applications use to perform their activities, such as displaying windows and graphics, managing memory, and so on. These procedures are sometimes referred to as the Windows application programming interface (API).