A chrestomathy is a sample of a given text in two or more different languages, for the purpose of teaching the different grammars and idioms.

m-w.com says
 1 : a selection of passages used to help learn a language
 2 : a volume of selected passages or stories of an author
In programming, chrestomathies are used to demonstrate the differences between different programming languages and paradigms. The most famous of these is the "Hello World!" Project, which is based on the canonical test program, HelloWorld. The larger programming chrestomathies have dozens or even hundreds of language samples, often including more than one example from a given language (to demonstrate different approaches to the problem).

''AFAIK, the word 'chrestomathy' was first applied to polyglot programming examples by EricRaymond, in the RetrocomputingMuseum's entry on the "99 Bottles of Beer" page [not, as previously asserted, the JargonFile's entry for HelloWorld]. Is anyone aware of any earlier examples of this usage? -- JayOsako''

Some chrestomathies on Wiki:
* ArraySumInManyProgrammingLanguages
* CounterInManyProgrammingLanguages
* DotProductInManyProgrammingLanguages
* WardNumberInManyProgrammingLanguages
* HexDumpInManyProgrammingLanguages
* http://c2.com/cgi/wiki?search=InManyProgrammingLanguages

Some chrestomathies elsewhere on the web:
* The RosettaCode wiki
* The LiterateProgramming wiki
* The ComputerLanguageBenchmarksGame
* A Practical Language Comparison: http://www.kochandreas.com/home/language/lang.htm
** Matrix with links to source: http://www.kochandreas.com/home/language/matrix.htm
* NinetyNineBottlesOfBeerOnTheWall: http://www.99-bottles-of-beer.net/

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See: CategoryInManyProgrammingLanguages