Most languages need some runtime. In the case of Lisp it starts with the basic memory management, since Lisp by default needs a garbage collector. This memory m

Most languages need some runtime. In the case of Lisp it starts with the basic memory management, since Lisp by default needs a garbage collector. This memory management is usually not provided by the operating system. It needs a basic interface to some OS stuff, threads, etc. A Lisp executable then can be one file which includes a runtime and the (compiled) Lisp code. One could also have these as two separate files. The there are two basic ways to provide the Lisp code: it's either just compiled code or a memory image of containing the code. SBCL uses the memory image approach. ECL (Embeddable Common Lisp) uses the 'compiled code' approach. ECL compiles to C and then adds the compiled C code to its runtime.