Publisher Summary It is noted that providing a combined definition of an abstract computer and its machine language is easier in many respects than defining a language and an evaluate function for the language within the language itself. This chapter presents Lisp-like language without a quote or label operator and with a modified conditional operator. It also describes semantics of the language. The formal semantics of Lisp has been defined by defining a function evaluate in the language of Lisp itself. To explore how to determine the value of any function defined in Lisp for any of its arguments, it is necessary to understand from the definition of the evaluate function how its values are determined for its arguments.