The traits of a system that is so simple for what it accomplishes that it actually frustrates you. For example:
	* WikiWikiWeb
	* ThePrevayler
	* quadrature phase decoders: it seems to require a complicated state machine; but it only needs an XOR gate to interface to the up/down counter. (I've been told the XOR circuit has been patented; one proof of its non-intuitiveness being that such a state machine was sold for many years. -- DavidCary)
	* TuringMachine
	* ForthLanguage (?)

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I spent two days proving why "isqrt.c" worked so we could extend it to 64 bits correctly. Seven lines of C resulted in two and a half pages of proof. We added merely three lines of code to shift the most significant two bits from the lower 32-bit dword to the higher dword and were done. -- SunirShah

Original (broken) link:
 http://snippets.org/snippets/portable/ISQRT+C.php3

Working links:

http://web.archive.org/web/20011115231728/http://www.snippets.org/snippets/portable/ISQRT+C.php3

or http://orion.planet.de/~jan/Snippets.9707/_d0912.html.

or http://c.snippets.org/snip_lister.php?fname=isqrt.c