Computer circuits distinguish between two different voltage levels to provide logical $0$ and $1\text{.}$ For example, logical $0$ may be represented by $0.0$ volts DC and logical $1$ by $+2.5$ volts DC. Or the reverse may be used—$+2.5$ volts as logical $0$ and $0.0$ volts as logical $1\text{.}$ The only requirement is that the hardware design be consistent. Fortunately, programmers do not need to be concerned about the actual voltages used.