“There are two ways to write error-free programs; only the third one works”

American computer scientist and Yale University professor Alan Perlis (1922-1990) wrote “Epigrams on Programming” for ACM’s SIGNPLAN (September 1982). One popular epigram is:
   
“40. There are two ways to write error-free programs; only the third one works.”
 
In other words, it is impossible to write an error-free computer program.
 
     
Wikipedia: Alan Perlis
Alan Jay Perlis (April 1, 1922 – February 7, 1990) was an American computer scientist and professor at Yale University known for his pioneering work in programming languages and the first recipient of the Turing Award.
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In 1982, he wrote an article, Epigrams on Programming, for ACM’s SIGPLAN journal, describing in one-sentence distillations many of the things he had learned about programming over his career. The epigrams have been widely quoted.[3] He remained at Yale until his death in 1990.
     
University of Tübingen—Prof. Dr. Herbert Klaeren
Epigrams on Programming
Alan J. Perlis
Yale University
This text has been published in SIGPLAN Notices Vol. 17, No. 9, September 1982, pages 7 - 13.
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40. There are two ways to write error-free programs; only the third one works.
 
Twitter
Adri Munier
‏@A3Munier
There are two ways to write error-free programs; only the third one works
http://www.csjokes.com/
5:43 AM - 26 Sep 2007
 
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Imran Raheem
‏@imranr_
There are two ways to write error-free programs; only the third one works - Alan Perlis, “Epigrams on Programming”
6:19 AM - 30 Sep 2009
 
iD Tech
Part I: Top 10 Programmer Jokes, Explained for the Rest of Us
by: Kendall on March 13, 2014
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3. There are two ways to write error-free programs; only the third one works.
This joke refers to the fact that it is actually impossible to write an error-free program.
 
It is possible to write a program that seems to have no errors, usually referred to as “bugs” in programmer lingo, but Lubarsky’s Law of Cybernetic Entomology states “There is always one more bug.” The bug may be so tiny and under such specific conditions that you’ll never see it… but there is always one more bug.
 
Since there is always one more bug, the joke says only the third, non-existent method is the only way to write an error-free program.