How many digits are used in the binary numbering system?

The binary numbering system is fundamentally a base-2 system, which means it utilizes only two distinct digits: 0 and 1. This limited range allows for the representation of all types of numerical values and data within electronic systems, including computers and aviation electronics. Each binary digit, or bit, can be either a 0 or a 1, creating a powerful combination for encoding information, as multiple bits can represent larger numbers or more complex data.

The choices emphasizing one digit, three digits, or four digits do not align with the definition of binary, as they suggest a limitation or expansion beyond the basic concept of binary representation. Only two digits are needed in binary to achieve any computational task, making two the correct answer to the question.