MIX is a hypothetical computer used in Donald Knuth

Donald Knuth

Donald Ervin Knuth is a computer scientist and Professor Emeritus at Stanford University.He is the author of the seminal multi-volume work The Art of Computer Programming. Knuth has been called the "father" of the analysis of algorithms...

's monograph, The Art of Computer Programming

The Art of Computer Programming

The Art of Computer Programming is a comprehensive monograph written by Donald Knuth that covers many kinds of programming algorithms and their analysis....

(TAOCP). MIX's model number is 1009, which was derived by combining the model numbers and names of several contemporaneous, commercial machines deemed significant by the author. (“MIX” also has the value 1009 in Roman numerals

Roman numerals

The numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...

.)

The 1960s-era MIX has since been superseded by a new (also hypothetical) computer architecture, MMIX

MMIX

MMIX is a 64-bit RISC instruction set architecture designed by Donald Knuth, with significant contributions by John L. Hennessy and Richard L. Sites...

, to be incorporated in forthcoming editions of TAOCP.