ENIAC’s patent, filed by John Presper Eckert and John Mauchly in 1947 and granted in 1964, later became famous for a second reason. In the 1973 case Honeywell v. Sperry Rand, a United States court ruled the ENIAC patent invalid and unenforceable, in part on the ground that key ideas derived from earlier work by John Atanasoff. The dispute is a reminder that the question of who built the first electronic computer is genuinely tangled.