Lasse said:
It's possible, and there were attempts in the early days of computers
to build decimal based computers. It just turned out to be too fragile.
Distinguishing between ten levels of voltage was more errorprone than
just between "on" and "off".
I believe both the Eniac and the Mark I were decimal.
The ASSC ("Mark I") was electromechanical, and used odometer-like wheels.
IBM, at least, never made a decimal computer based on voltage
differences. All IBM decimal computers used binary encodings, including:
BCD: 0000 through 1001.
Excess-3: 0011 through 1100
Biquinary: five bits, only one 1, plus two bits, only one 1
Three-of-five: five bits, three 1, and two 0
IBM mainframes still normally use decimal arithmetic for financial
calculations, although binary is used for addressing and scientific
number crunching.
One Russian computer of the 50's used ternary (base-3).