Correct Answer:
B. Binary
The correct answer is B: Binary. A computer primarily uses the binary number system. This system is fundamental to how computers operate because their internal circuitry is built with electronic switches that are either on or off. These two states directly correspond to the two digits in the binary system: 0 (off) and 1 (on). All data, instructions, and operations within a computer are ultimately represented and processed using sequences of these binary digits, or bits.
- A: Decimal is incorrect. The decimal system (base-10) is what humans commonly use, but computers do not use it as their primary internal number system. While computers can convert binary to decimal for human readability, their core processing is not in decimal.
- C: Hexadecimal is incorrect. The hexadecimal system (base-16) is often used in computer science for compactly representing binary data, as each hexadecimal digit can represent four binary digits. It is a convenience for programmers and hardware engineers, but it is not the computer's primary internal system.
- D: Octal is incorrect. The octal system (base-8) is similar to hexadecimal in that it's a compact way to represent binary data (each octal digit represents three binary digits). While historically used, it is less common than hexadecimal today and is certainly not the computer's primary internal number system.