A properly programmed computer can calculate crucial parameters for nuclear bomb design, ignition, and explosive yields, so it can predict what to expect from an experiment. Of course, “experiment” means the actual detonation of a nuclear bomb, either in a test or in warfare. During the Manhattan Project, in the 1940s, Los Alamos used mechanical calculators and early IBM punch-card tabulators to calculate atomic bomb yields. Decade by decade, as computing power increased exponentially, so too did the power to calculate and understand in detail the nuclear happenings in a nuclear explosion. And the needs of Los Alamos fostered the sustained quest to build the fastest computer in the world.