Programming Freedom - February 1995 - Number 11

League For Programming Freedom
1 Kendall Square #143
P.O. Box 9171
Cambridge, MA 02139

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Letter to the Patent Office From Professor Donald Knuth

Professor Donald Knuth of Stanford University is the world's leading authority on algorithms. His magnum opus, the three volume work the "The Art of Computer Programming," is the most important reference work on algorithms. Knuth also developed the mathematical text formatter TeX and the idea of "literate programming". Supporting evidence of Knuth's position are the following distinctions:

National Medal of Science
Member, National Academy of Sciences
Member, National Academy of Engineering
Fellow, American Academy of Arts and Sciences
Turing Award, Association for Computing Machinery
18 Honorary Doctorates

The first four of these distinctions are the highest American awards for scientists. Since there is no Nobel prize in computing, the receipt of the Turing award is often regarded as having a similar status.

Through these honors, Knuth is perhaps the most distinguished living exponent of the field of computer science. He is also now a member of the League for Programming Freedom.

Here is the letter he sent in February 1994 to the Patent Commissioner on the subject of software patents.

Commissioner of Patents and Trademarks
Box 4
Patent and Trademark Office
Washington, DC 20231

Dear Commissioner:

Along with many other computer scientists, I would like to ask you to 
reconsider the current policy of giving patents for computational 
processes.  I find a considerable anxiety throughout the community of 
practicing computer scientists that decisions by the patent courts and the 
Patent and Trademark Office are making life much more difficult for 

In the period 1945-1980, it was generally believed that patent law did not 
pertain to software.  However, it now appears that some people have 
received patents for algorithms of practical importance - e.g., Lempel-Ziv 
compression and RSA public key encryption - and are now legally preventing 
other programmers from using these algorithms.

This is a serious change from the previous policy under which the computer 
revolution became possible, and I fear this change will be harmful for 
society.  It certainly would have had a profoundly negative effect on my 
own work: For example, I developed software called TeX that is now used to 
produce more than 90% of all books and journals in mathematics and physics 
and to produce hundreds of thousands of technical reports in all scientific 
disciplines.  If software patents had been commonplace in 1980, I would not 
have been able to create such a system, nor would I probably have ever 
thought of doing it, nor can I imagine anyone else doing so.

I am told that the courts are trying to make a distinction between 
mathematical algorithms and nonmathematical algorithms.  To a computer 
scientist, this makes no sense, because every algorithm is as mathematical 
as anything could be.  An algorithm is an abstract concept unrelated to 
physical laws of the universe.

Nor is it possible to distinguish between "numerical" and "nonnumerical" 
algorithms, as if numbers were somehow different from other kinds of 
precise information.  All data are numbers, and all numbers are data.  
Mathematicians work much more with symbolic entities than with numbers.

Therefore the idea of passing laws that say some kinds of algorithms belong 
to mathematics and some do not strikes me as absurd as the 19th century 
attempts of the Indiana legislature to pass a law that the ratio of a 
circle's circumference to its diameter is exactly 3, not approximately 
3.1416.  It's like the medieval church ruling that the sun revolves about 
the earth.  Man-made laws can be significantly helpful but not when they 
contradict fundamental truths.

Congress wisely decided long ago that mathematical things cannot be 
patented.  Surely nobody could apply mathematics if it were necessary to 
pay a license fee whenever the theorem of Pythagoras is employed.  The 
basic algorithmic ideas that people are now rushing to patent are so 
fundamental, the result threatens to be like what would happen if we 
allowed authors to have patents on individual words and concepts.  
Novelists or journalists would be unable to write stories unless their 
publishers had permission from the owners of the words.  Algorithms are 
exactly as basic to software as words are to writers, because they are the 
fundamental building blocks needed to make interesting products.  What 
would happen if individual lawyers could patent their methods of defense, 
or if Supreme Court justices could patent their precedents?

I realize that the patent courts try their best to serve society when they 
formulate patent law.  The Patent Office has fulfilled this mission 
admirably with respect to aspects of technology that involve concrete laws 
of physics rather than abstract laws of thought.  I myself have a few 
patents on hardware devices.  But I strongly believe that the recent trend 
to patenting algorithms is of benefit only to a very small number of 
attorneys and inventors, while it is seriously harmful to the vast majority 
of people who want to do useful things with computers.

When I think of the computer programs I require daily to get my own work 
done, I cannot help but realize that none of them would exist today if 
software patents had been prevalent in the 1960s and 1970s.  Changing the 
rules now will have the effect of freezing progress at essentially its 
current level.  If present trends continue, the only recourse available to 
the majority of America's brilliant software developers will be to give up 
software or to emigrate.  The U.S.A.  will soon lose its dominant position.

Please do what you can to reverse this alarming trend.  There are far 
better ways to protect the intellectual property rights of software 
developers than to take away their right to use fundamental building 

Donald E. Knuth
Professor Emeritus