Common Lisp is a general-purpose programming language in the Lisp language family. Its syntax is defined on top of s-expressions, however it can be extended through the use of reader macros. It supports compile-time meta-programming through the use of macros. It supports the OOP paradigm through the Common Lisp Object System. The API upon which CLOS is implemented is exposed to the programmer so they can extent the object system. This API is refered as the Meta-Object Protocol. There are multiple implementations available: SBCL, which generates fast code, CCL, which compiles code fast, ABCL, which runs on the JVM, JSCL which runs on Node, and the browser, etc.