A library called X Library (Xlib) encapsulates this protocol by a set of application programming interfaces (API), so that X clients can do everything in terms of function calls.

• 一个称为X库（Xlib）的函数库用一套应用程序编程接口（applicationprogramminginterfaces,API）的形式封装了这套协议，这样X客户程序就可以调用所有的函数。