MMIX
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MMIX is a virtual machine which simulates a RISC processor. Donald Knuth uses the MMIX in his multi-volume 'The Art of Computer Programming to describe the low-level implementation of algorithms. He deliberately chooses to describe algorithms in both English and a hypothetical assembly language so that the programs will not be outdated easily because of the proliferation of new computer programming languages. Additionaly a formalism which is hardware-related helps to illustrate problems of efficiency.
See also: MIX
Literature: Donald E. Knuth (Heidelberg: Springer-Verlag, 1999), viii+550pp. MMIXware A RISC Computer for the Third Millennium
(Lecture Notes in Computer Science, no. 1750.[1])
MMIX is also the Roman numeral for the year 2009.