WCL is a Common Lisp implementation
that provides Common Lisp as a Unix shared library that can be linked with Lisp and C code to produce efficient applications. The goal of WCL is to allow hundreds of Lisp applications to be realistically available at once, while allowing many of them to run concurrently. For example, the executable for a Lisp version of the canonical ``Hello World!'' program requires only 20k bytes.