Why would they need to build a digital computer? How about an analog one. A good example is Moniac http://en.wikipedia.org/wiki/MONIAC_Computer http://en.wiki

Why would they need to build a digital computer? How about an analog one. A good example is Moniac http://en.wikipedia.org/wiki/MONIAC_Computer http://en.wikipedia.org/wiki/MONIAC_Computer It uses water to model an economy. Taps can be used to change variables (eg interest rates). If the Romans wanted to do engineering calculations then there is no requirement for digital - an analog computer could do the calculations just fine. You can imagine taps to set lengths, widths, heights etc.