Portable, extended Scheme with reflective object(-oriented) system, operating system services, modules, threads, many system programming features (integrates with, compiles to C or bytecodes) and useful extensions. [Open Source]

Embeds Scheme in Common Lisp.

A portable Scheme implementation written by Matthias Blume of Princeton University. No longer actively developed.

A portable Scheme implementation written by Aubrey Jaffer.

A portable, high-performance implementation of Scheme based on an optimizing compiler by Marc Feeley. Developed at University of Montreal.

An interactive multithreaded Scheme interpreter with turtle graphics for Windows 95, based on SCM.

A free R4RS Scheme interpreter which can access the Tk graphical package.

From Erian Concept, has CLOS-like object system; runs on Be/x86, FreeBSD, Linux/x86, Solaris (SPARC, x86), Windows. [commercial, unlimited free download evaluation copy with registration]

A superset of the Scheme dialect of Lisp with extensions to support object-oriented programming.

From MIT, for many systems, has comprehensive code library, includes most functionality of ANSI Standard Common Lisp (CLtL2), many low-level OS interactions. Distributed with system is LIAR (LIAR Imitates Apply Recursively), optimizing compiler that outputs native machine code, has Edwin interactive Emacs-derived editor written in pure Scheme and the subject of an MIT AI Lab Memo. Arguably one of the best Scheme systems available, unarguably one of largest. Major downfall: its not totally R5RS compliant, more so for hygienic macros and #f versus the empty list. Version 7.5 now available for x86 systems.

A R5RS Scheme interpreter which integrates with C, allowing calling of C functions and accessing C variables from Scheme. It provides a mechanism to load C shared libraries. It runs on x86 and PowerPC based Linux systems.

A fast, small Scheme interpreter which is mostly compliant with the R5RS standard.

Portable Scheme implementation, conforms to IEEE/ANSI standard, supports all features of R5RS Report, many features of Chez Scheme and various SRFIs. Derived from XScheme: object system dropped, many changes, additions.

Newer versions here. Scheme system for the Palm Pilot PDA developed by Fred Bayer.

Texas Instruments system for DOS OS; no longer maintained; download formats: source, executable/binary.

Even more Scheme implementations freely available from the Indiana U. repository.

Scheme-like language developed at Yale; is to Scheme rather as NIL is to Lisp; mainly of interest to historians and theoreticians. FTP for v3.1.

A list of Scheme implementations from the Scheme FAQ maintained by Mark Kantrowitz.

HTMLified by Margaret Fleck, one of the authors of Envision.

Two systems for Windows with built in "industrial-strength" solid modeler based on the ACIS solid modeler Geometric Modeling Kernel.

Interpreter for Macintosh or Windows. Has "friendly and convenient interactive programming environment" with language sensitive editor, full documentation. [commercial, free 14 day download]

Ksi is a portable, embeddable Scheme implementation written in C. Unfortunately its documentation is all in Russian at this point.

Very small, portable implementation, has some database, Unix programming, CGI scripting extensions. Runs on DOS, Linux, Unix, Windows. Free source downloads.

A small and portable implementation based on a bytecode interpreter designed to be used as a testbed for experiments in implementation techniques.

A tiny implementation of Scheme based on MiniSCHEME. It provides almost complete coverage of R5RS Scheme. Geared towards embedded scripting use, but also functions as a standalone interpreter and extensible shell tool. Recent changes have gotten the executable size down to approximately 64KB on Linux/x86.

Fred Bayers home page is really the home of this Scheme for 3COM Pilot PDA systems: compiler and runtime system intended mainly as a tool to quickly try ideas and algorithms, but can write dialog-based applications.

Derived from STkn implementation based on an ad-hoc virtual machine, byte compiler; compilable as library to embed in other programs, has object system with MOP, multiple inheritance, generic functions, multimethods, module system, full R5RS tower of numbers, link to GTK+ X toolkit; almost R5RS compliant (in process), to support as many final SRFIs as possible, now supports SRFI-6.

The FAQ for Scsh, the Scheme Shell.

DEC's venerable Scheme to C translator which runs on most anything with an ANSI C compiler.

A compact (<64 Kb) implementation of R4RS Scheme that compiles for VxWorks/Tornado (and is integrated with the system symbol table). [Open source, Artistic License]

Scheme environment for Windows 3.1/95; interpreter independent, though defaults to Jaffer's SCM. Used at University of Lille 1, France, for introductory programming course. Free downloads. English, Française.

Statically-typed Scheme dialect, written in Infer, combines many of the best features of Scheme and ML. NSF funded.

A powerful optimizing Scheme compiler from Jeffery Mark Siskind at the NEC Research Institute. Sacrifices functions such as call/cc in favor of efficiency, but generated code is remarkably bulletproof and fast.

Full Scheme programming environment for Macintosh, many Unixes, Windows. Has module and object systems, platform-independent graphics. Ideal for beginners; one of the major design goals is a flexible teaching environment.

Yet more Scheme implementations from the CMU AI Repository. Many of these are also available from the Indiana University Scheme Repository.

For MIPS, SH3, ARM-based Windows CE devices. Supports Aubrey Jaffer's SLIB, has initialization file for same, parenthesis-balancing text editor. Windows NT version exists. [Open Source, Artistic License]

A commercial Scheme which is freely available for non-commercial use on Linux and FreeBSD. It has support for several features like bitmap/greymap processing and can be used as a general tool for image processing, OCR or specialized optical object and pattern recognition.

Small, embeddable, scripting PLT Scheme implementation: R5RS compliant, full numerical tower, threads (all platforms), exceptions, modules, class-based objects, regular-expression matching, TCP/IP. For Macintosh, Unix, Windows 32-bit.

Advocacy and authoring group, umbrella name for family of implementations: DrScheme (Scheme, MzScheme, MrEd); books: How to Design Programs, How to Use Scheme; and TeachScheme! project. University-based, supported by many volunteers writing code, documentation.

System with one goal: enable Scheme-based programming style where C(++) is usually needed; makes Scheme practical via features found in most traditional languages but not Scheme and functional programming. [Open Source, GPL]

Language designed and largely implemented, now a matter of coding, documenting. Goals: high consistency; improve language's functional nature; consistency with lambda calculus; optimize, but not at cost of other goals.

A Scheme interpreter implemented as a library which can be embedded into C programs, as well as a standalone interpreter. Mostly R5RS, Guile compatible, and includes regular expressions and most Posix functions.

A portable scheme interpreter by Britt Park. Also other free software, including: Cdoc - a simple program to generate pretty TeX output from annotated c or c++ code; Userblock - a simple user space block device driver kit for Linux; UVFS - a user space filesystem kit.

(new site) An embeddable, reusable extension language subsystem for applications written in C or C++. Elk is also a useful standalone Scheme implementation with interfaces to POSIX, Unix, and X11.

A Scheme compiler which compiles a subset of R5RS into C. Uses the ideas presented in Baker's paper "Cheney on the MTA". It is highly portable, reasonably efficient and makes interfacing to C and C++ very easy.

An R5RS Scheme implementation developed to be a handy script interpreter. Quick startup, built-in system interface, native multilingual support. [Open source, BSD license]

An implementation of the Scheme language in OCaml. The primary purpose of Schoca is the use as an embedded extension language in OCaml applications. [Open source, GPL]

A distributed implementation of Scheme that permits efficient transmission of higher-order objects such as closures and continuations.

A Scheme implementation. [Commercial]

A complete Scheme system that is fully compatible with Chez Scheme but uses high-speed threaded interpreter technology in place of Chez Scheme's incremental native-code compiler. [Freeware]

An lightweight implementation of Scheme in C++. [Open source, zlib license]

A nearly R5RS compliant Scheme compiler with multiple backends, currently including .NET, JVM, and C. [Public Domain]

(old site, last update in 1997) An embeddable, reusable extension language subsystem for applications written in C or C++. Elk is also a useful standalone Scheme implementation with interfaces to POSIX, Unix, and X11.