And the first thing you do to them is to convert them to binary. Look at any Ethernet PHY for example - you have that nice 5-level signal coming on.. and the f

And the first thing you do to them is to convert them to binary. Look at any Ethernet PHY for example - you have that nice 5-level signal coming on.. and the first thing you do is feed it into AFE/ADC so you get digital signals that you can actually work with. So yes, in some specific situations, like Flash memory or interconnects, there are multi-level signals. But the computing itself is always binary.