Scheme is a statically scoped and properly tail-recursive dialect of the Lisp programming language invented by Guy Lewis Steele Jr. and Gerald Jay Sussman. It was designed to have an exceptionally clear and simple semantics and few different ways to form expressions. A wide variety of programming paradigms, including imperative, functional, and message passing styles, find convenient expression in Scheme.

Scheme was one of the first programming languages to incorporate first class procedures as in the lambda calculus, thereby proving the usefulness of static scope rules and block structure in a dynamically typed language. Scheme was the first major dialect of Lisp to distinguish procedures from lambda expressions and symbols, to use a single lexical environment for all variables, and to evaluate the operator position of a procedure call in the same way as an operand position. By relying entirely on procedure calls to express iteration, Scheme emphasized the fact that tail-recursive procedure calls are essentially goto's that pass arguments. Scheme was the first widely used programming language to embrace first class escape procedures, from which all previously known sequential control structures can be synthesized. More recently, building upon the design of generic arithmetic in Common Lisp, Scheme introduced the concept of exact and inexact numbers. Scheme is also the first programming language to support hygienic macros, which permit the syntax of a block-structured language to be extended reliably.

MIT/GNU Scheme

MIT/GNU Scheme is a complete programming environment that runs on many unix platforms, as well as Microsoft Windows and IBM OS/2. It features a rich runtime library, a powerful source-level debugger, a native-code compiler, and an integrated Emacs-like editor.


Other Implementations


Send bug reports and other communications concerning MIT Scheme to bug-cscheme at

Last updated 23 October 2003.

This page is maintained by Chris Hanson.

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