What term is used for a number system that represents an on or off state?

The correct choice is binary, as it is the fundamental number system that operates on the basis of two distinct states: on and off. In the binary system, these states are represented by the digits 0 and 1. This system is the backbone of all modern computing, as digital circuits and processors utilize these binary states to perform calculations, store data, and execute instructions.

Each digit in a binary number is referred to as a bit, which directly correlates with the electrical states of a computer hardware component—either having an electrical charge (on) or not (off). Consequently, all complex data types and structures in computing can ultimately be broken down into binary representations, demonstrating the critical importance of this number system.

In contrast, the hexadecimal system is a base-16 number system that extends beyond binary, using digits 0-9 and letters A-F to represent values. The decimal system, known as base-10, comprises the digits 0-9 and is more natural for human comprehension but doesn't directly represent on/off states like binary does. ASCII, which stands for American Standard Code for Information Interchange, is a character encoding standard that uses binary values to represent text and symbols rather than being a number system itself.