them taking courses from Adele Goldstine, Mary Mauchly, and Mildred Kramer. Each gun required its own firing table, which had about 1,800 trajectories. Computing just one trajectory required approximately 30–40 hours of handwork with a calculator. After two or three months, Antonelli and Bilas were moved to work on the differential analyser in the basement of the Moore School, the largest and most sophisticated analogue mechanical calculator of the time, of which there were only three in the United States and five or six in the world (all of the others were in Great Britain). The analyser had been lent to the University of Pennsylvania for the duration of the war. Using the analyser (invented by Vannevar Bush of MIT a decade prior and made more precise with improvements by the Moore School staff), a single trajectory computation—about 40 hours of work on a mechanical desk calculator—could be performed in about 50 minutes. Antonelli was further promoted to supervising calculations on the analyser. The analyser room staff worked six days a week, with their only official holidays as Christmas and the Fourth of July. Working with ENIAC The Electronic Numerical Integrator And Computer was developed for the purpose of performing these same ballistics calculations between 1943 and 1946. In June 1945, Antonelli was selected to be one of its first programmers, along with several other women from the computer corps: Betty Snyder, Marlyn Wescoff, and Ruth Lichterman, and a fifth computer named Helen Greenman. When Greenman declined to go to Aberdeen for training and a 1st alternate refused as well, Betty Jean Jennings, the 2nd alternate, got the job, and between June and August 1945 they received training at Aberdeen Proving Grounds in the IBM punched card equipment that was to be used as the I/O for the ENIAC. Later, Antonelli's college schoolmate and fellow computer, Bilas, would join the team of ENIAC programmers at the Moore School, though she did not attend the initial training at Aberdeen. The computer could complete the same ballistics calculations described above in about 10 seconds, but it would often take one or two days to set the computer up for a new set of problems, via plugs and switches. It was the computer programmer's responsibility to determine the sequence of steps required to complete the calculations for each problem and set up the ENIAC according; early on, they consulted with ENIAC engineers such