Dartmouth College, 131 decade, 118 decimal digit, 11, 14 decimal position, 118 deciphering, 184, 188 decoding, 184, 188 definite integral, 111, 225 delay lines, 17, 20, 171-2 dendrite, 3 denial, 147 dependent variable, 81, 224 derivative, 68-71, 225 design of mechanical brains, 167-79, 251 desk calculating machines, 4, 11, 17, 19 detail cards, 50 dial switch, 92, 95-6 dial telephone, 17, 19, 128 differences, 110, 227 differential, 68, 70, 78 differential analyzer, 68, 72-88, 239-41 Differential Analyzer No. 2, 65-88; accuracy, 86; cost, 87; reliability, 87; speed, 87 differential equation, 68-9, 71, 111, 141, 225-6 differential function, 70 differential gear assembly, 78 digit, 11, 14 Digit Pickup, 60 digit selector, 60 digit tray, 119 digit trunk lines, 119 digit trunks, 119 digital machines (machines that handle information expressed as digits or letters): Bell Laboratories’ general-purpose relay calculator, 128-43; Eniac, 113-27; Harvard IBM Automatic Sequence-Controlled Calculator, 89-112; punch-card calculating machinery, 42-64; references, 232-9, 245-55 directions, 24 disc, 78-80 discrimination, 140 discriminator, 140-1 distance, 68-9 distinguishing _A_ and _H_, 184 dividend, 103, 223 Divider-Square-Rooter, 115-7 dividing, 55-6, 98, 102, 121, 140 divisor counter, 102 doorpost, 65-6 doubling, 76-7, 100 doubling mechanism, 76-7 drafting rules, 149 drag coefficient, 80 drive, 86 Dry Ice, 190 echo, 171 Eckert-Mauchly Computer Corporation, 179, 250 economic relations, 194 Edsac, 249 “educated” machine, 101 Edvac, 177, 249 Egyptian, 12 either, 149 electric charge, 172 electric remote-control accounting, 250 electric typewriter, 91, 97, 236 electromagnet, 168 Electronic Binary Automatic Computer, 179 electronic calculating punch, 236 Electronic Control Company, 250 Electronic Numerical Integrator and Calculator (Eniac), 113-27, 246-7; _see also_ Eniac electronic tubes, 17, 20-1, 178-9; Cathode, 21; Grid, 21; Plate, 21 electrostatic storage tube, 17, 20, 172 11 position, 45 11 punch, 58 else, 146-7 end-around-carry, 95, 217, 223 engine, 90 Eniac, 113-27, 246-7; cost, 126; panels, 115; reliability, 126; speed, 125; unbalance, 124 “enough alike,” 184 Equal (output of sequencer), 61-2 equation, 68, 225 equivalent, 14 erase key, 134 Etruscan, 188 explanation, 209-13 explicit equation, 86 exponential, 85, 106, 225-6 extraction, 222