I'm taking a computer system design course and my professor told us that in digital systems, the conventional voltages used to denote a digital 0 and a digital 1 have changed over the years.
Apparently, back in the 80s, 5 V was used as a 'high' and 1 V was used to denote a 'low'. Nowadays, a 'high' is 0.75 V and a 'low' is around 0.23 V. He added that in the near future, we may shift to a system where 0.4 V denotes a high, and 0.05 V, a low.
He argued that these values are getting smaller so that we can reduce our power consumption. If that's the case, why do we take the trouble to set the 'low' to any positive voltage at all? Why don't we just set it to the true 0 V (neutral from the power lines, I guess) voltage?