Gerhard Postpischil's functional description is correct, and John Ehrman's acronym is all but correct.
According to The IBM 704 Electronic Data Processing Machine Manual of Operations, Form 24-6661-2, undated but copyright 1954, 1955, CSA is an acronym for Compare Accumulator with Storage. It is of course an implementation of what mathematicians call signum. One of the terrrible legacies not of Dijkstra himself but of his epigoni is that ternary branches have been banished from modern statement-level procedural languages. John Gilmore Ashland, MA 01721-1817 USA
