Which base is used by the octal numeral system?

Which base is used by the octal numeral system?

• A. 8
• B. 7
• C. 4
• D. 10

Answer: (A)

Octal uses base 8, meaning each position in an octal number represents a power of eight and only eight digits are used: 0 through 7. Each step to the left multiplies by 8 (8^1, 8^2, and so on). This base is why octal numbers line up nicely with groups of three bits in binary, since three bits can produce exactly eight different values (0–7). So the base used by the octal system is eight. In contrast, a base would use digits 0–6 for seven digits, base-4 would use 0–3, and base-10 uses 0–9.

Octal uses base 8, meaning each position in an octal number represents a power of eight and only eight digits are used: 0 through 7. Each step to the left multiplies by 8 (8^1, 8^2, and so on). This base is why octal numbers line up nicely with groups of three bits in binary, since three bits can produce exactly eight different values (0–7). So the base used by the octal system is eight. In contrast, a base would use digits 0–6 for seven digits, base-4 would use 0–3, and base-10 uses 0–9.