ACL2 Version 3.6.1

ACL2 is both a programming language in which you can model computer systems and a tool to help you prove properties of those models.

ACL2 is part of the Boyer-Moore family of provers, for which its authors have received the 2005 ACM Software System Award.


Start Here: Applications, Tours, and Tutorials/Demos ACL2 Workshops and UT ACL2 Seminar
Books and Papers about ACL2 and Its Applications The User's Manual and Hyper-Card
Lemma Libraries and Utilities Mailing Lists
Recent changes to this page Obtaining and Installing Version 3.6.1
Differences from Version 3.5 Other Releases
How to contribute libraries and documentation

Matt Kaufmann and J Strother Moore
University of Texas at Austin
February 17, 2010

We gratefully acknowledge substantial support from the following. (These are included in a much more complete acknowledgments page.)

The User's Manual

ACL2's user manual is a vast hypertext document. You can wander through it here, in its HTML format.

Here are the two common entries to the documentation graph:
Major Topics (Table of Contents)
Index of all documented topics
The tiny warning signs, , indicate that the links lead out of introductory level material and into reference manual material. Once in the reference manual, virtually all links are into the manual and none of them is marked with the warning sign! It is easy for the newcomer to get lost.

Here is how we recommend you use this documentation.

If you are a newcomer to ACL2, we do not recommend that you wander off into the full documentation. Instead start with the tours and perhaps the demos.

If you are still interested in ACL2, we recommend that you get a copy of Computer-Aided Reasoning: An Approach and read it carefully. Work the exercises with ACL2. Learn ``The Method.''

Less effective than reading the book and doing the exercises, but still useful, is to read selected papers from Books and Papers about ACL2 and Its Applications, read the documentation topic the-method, and the Hyper-Card and then work your way through the tutorials.

Then, we recommend you read selected topics from ``Major Topics'':

Finally, experienced users tend mostly to use the ``Index'' to lookup concepts mentioned in error messages or vaguely remembered from their past experiences with ACL2.

Note: If ACL2 has been installed on your local system, the HTML documentation should also be available locally. You can minimize network traffic by browsing your local copy. Suppose ACL2 was installed on /usr/jones/acl2/vi-j. Then the local URL for this page is
Many ACL2 users set a browser bookmark to this file and use their browser to access the documentation during everyday use of ACL2. If you obtain ACL2, please encourage users to use the local copy of the documentation rather than access it across the Web.

Note: The documentation is available in four forms: Postscript (which prints as a book over 1500 pages long), HTML, EMACS Texinfo, and ACL2's own :DOC commands. The documentation, in all but the Postscript form, is distributed with the source code for the system. So if you have already obtained ACL2, you should look in the doc/ subdirectory of the directory upon which ACL2 is installed. You may obtain the gzipped Postscript form of the documentation by clicking here (approaching 2 MB).

Lemma Libraries and Utilities; and, How to Contribute

The distribution of ACL2 includes some tools built by users. Most of these are ACL2 ``books,'' which are collections of definitions and theorems you might find useful in your models and proofs. Most of the available books come with the distribution, but the above link will also take you to additional books in support of the ACL2 Workshops (``workshops'') and non-standard analysis (``nonstd'').

We strongly encourage users to submit additional books by following the instructions for contributing books to ACL2.

We also distribute a few interface tools, such as support for infix printing. For these, see the Utilities section of Books and Papers about ACL2 and Its Applications. Some of the papers mentioned in that collection contain utilities, scripts, or ACL2 books the problem domains in question.

How to contribute libraries and documentation

As mentioned above, we strongly encourage users to submit additional books by following the instructions for contributing books to ACL2.

Also, if you have written up (or are interested in writing) text that may be helpful to other ACL2 users, we invite you to contribute it to the community. Such user documentation may be in any format that is readable by web browsers (for example html, pdf, and plain text). User-contributed documentation can link back to the ACL2 documentation proper, by using links such as:
(In general, substitute the upper-case of the documentation topic for "MAKE-EVENT" in the example above.)

To contribute user documentation, send email to the ACL2 developers, for example at