— Pablo Picasso Spanish painter, sculptor, printmaker, ceramicist, and stage designer 1881 - 1973
As discussed in this entry from Quote Investigator http://quoteinvestigator.com/2011/11/05/computers-useless/#more-2932, the origin seems to be the article "Pablo Picasso: A Composite Interview" by William Fifield which appeared in The Paris Review 32, Summer-Fall 1964, and collected a number of interviews Fifield had done with Picasso.
Common later variant: "Computers are useless. They can only give you answers." This variant seems to have arisen in the 1980s, the earliest known appearance in a book is Herman Feshbach, "Reflections on the Microprocessor Revolution: A Physicist's Viewpoint", in Man and Technology (1983), ed. Bruce M. Adkins, where the attribution is described as "rumoured". http://books.google.com/books?id=9EohAQAAIAAJ&q=Picasso<!--