Editing Computer science (section)

==Discoveries==
The philosopher of computing [[William J. Rapaport|Bill Rapaport]] noted three ''Great Insights of Computer Science'':<ref>{{cite web|url=http://www.cse.buffalo.edu/~rapaport/computation.html|title=What Is Computation?|publisher=State University of New York at Buffalo|last=Rapaport|first=William J.|date=20 September 2013|access-date=August 31, 2013|archive-date=February 14, 2001|archive-url=https://web.archive.org/web/20010214002845/http://www.cse.buffalo.edu/~rapaport/computation.html|url-status=live}}</ref>
* [[Gottfried Wilhelm Leibniz]]'s, [[George Boole]]'s, [[Alan Turing]]'s, [[Claude Shannon]]'s, and [[Samuel Morse]]'s insight: there are only ''two objects'' that a computer has to deal with in order to represent "anything".{{refn |group="note"|The word "anything" is written in quotation marks because there are things that computers cannot do. One example is: to answer the question if an arbitrary given computer program will eventually finish or run forever (the [[Halting problem]]).}}
:: All the information about any computable problem can be represented using only 0 and 1 (or any other bistable pair that can flip-flop between two easily distinguishable states, such as "on/off", "magnetized/de-magnetized", "high-voltage/low-voltage", etc.).
{{see also|Digital physics}}
* [[Alan Turing]]'s insight: there are only ''five actions'' that a computer has to perform in order to do "anything".
:: Every algorithm can be expressed in a language for a computer consisting of only five basic instructions:<ref>B. Jack Copeland, (2012). ''Alan Turing's Electronic Brain: The Struggle to Build the ACE, the World's Fastest Computer''. OUP Oxford. p. 107. {{ISBN|978-0-19-960915-4}}.</ref>
::* move left one location;
::* move right one location;
::* read symbol at current location;
::* print 0 at current location;
::* print 1 at current location.
{{see also|Turing machine}}
* [[Corrado Böhm]] and Giuseppe Jacopini's insight: there are only ''three ways of combining'' these actions (into more complex ones) that are needed in order for a computer to do "anything".<ref>Charles W. Herbert, (2010). ''An Introduction to Programming Using Alice 2.2''. Cengage Learning. p. 122. {{ISBN|0-538-47866-7}}.</ref>

:: Only three rules are needed to combine any set of basic instructions into more complex ones:
::*''sequence'': first do this, then do that;
::* '' selection'': IF such-and-such is the case, THEN do this, ELSE do that;
::* ''repetition'': WHILE such-and-such is the case, DO this.
:: The three rules of Boehm's and Jacopini's insight can be further simplified with the use of [[goto]] (which means it is more elementary than [[structured programming]]).
{{see also|Structured program theorem}}