Assuming that the power supply is 5V, a voltage greater than 4V becomes a high voltage (called a high level in technical terms), which is recorded as a logic 1, and a voltage lower than 1V becomes a low voltage (called a low level in a technical term), and is recorded as a logic 0. Now, We use circuits to implement AND operations, and the corresponding circuits are called AND gates, see the picture:
It can be seen that if and only when the input is logic 1, the result is 1, which is the AND gate circuit. Isn't this just multiplication in a computer?
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