ENIAC

"The ENIAC was not completed until the fall of 1945, after the war had ended. The ballistic tables ENIAC was built to compute no longer required urgent attention. But the ENIAC was a military machine, and so was inmediately turned to the military ends of the rapidly emerging Cold War. The first problem programmed in the machine was a mathematical model of a hydrogen bomb from the Los Alamos atomic weapons laboratories. The ENIAC, unable to store programs or retain more than twenty ten-digits numbers in its tiny memory, required several weeks in November 1945 to run the program in a series of stages. The program involved thousand of steps, each individually entered into the machine via its plug-boards and switches, while the data for the problem occupied one million punch cards. The program's results exposed several problems in the proposed H-bomb design. The director of Los Alamos expressed his thanks to the Moore school in March 1946, writing that "the complexity of these problems is so great that it would have been impossible to arrive at any solution without the aid of ENIAC (Paul N. Edwards. The Closed World).