ENIAC

ENIAC (Electronic Numerical Integrator And Computer) was the first all electronic (that is, it used the properties of electrons to achieve it's results, different from the mechanical computers put together by the likes of Wilhelm Schickard, Blaise Pascal, and the famous Charles Babbage) digital (calculations in discrete digits) computer. It was developed and built by the U.S. Army with the purpose of calculating ballistic firing tables. ENIAC was designed by J. Presper Eckert and John William Mauchly and was operational in 1946.

ENIAC was a decimal machine using ten position Ring counters to store digits. Arithmetic was performed by "counting" pulses with the Ring counters and generating carry pulses if the counter "wrapped around". The idea being to emulate in electronics the operation of the digit wheels of a mechanical adding machine.