Ross Quinlan as an improved version of his prior algorithm, C4.5, which itself is an improvement over his Iterative Dichotomiser 3 (ID3) algorithm. Although Quinlan markets C5.0 to commercial clients (see http://www. rulequest.com/ for details), the source code for a single-threaded version of the algorithm was made publically available, and it has therefore been incorporated into programs such as R.