1. The algebra of logic can be used in the calculation of some electrical circuits.
2. Some electrical circuits can be used in the calculations of the algebra of logic.
This fact is what led to the next step.
LOGICAL-TRUTH CALCULATION
BY MACHINE
In 1946 two undergraduates at Harvard University, Theodore A. Kalin and William Burkhart, were taking a course in mathematical logic. They noticed that there were a large number of truth tables to be worked out. To work them out took time and effort and yet was a rather tiresome automatic process not requiring much thinking. They had had some experience with electrical circuits. Knowing of Shannon’s work, they said to each other, “Why not build an electrical machine to calculate truth tables?”
They took about two months to decide on the essential design of the machine:
1. The machine would have dial switches in which logical connectives would be entered.
2. It would have dial switches in which the numbers of statements like 1, 2, 3 ··· would be entered.
3. It would scan the proper truth table line by line by sending electrical pulses through the dial switches.
4. It would compute the truth or falsehood of the whole expression.