Octal system digit symbols – UGC NET Question

The system that uses digits from 0 to 7 is known as the octal number system. The prefix “oct” indicates eight, reflecting the eight different symbols used. In octal, each position represents powers of 8, such as 1, 8, 64 and so on. Hence the correct name for this base-8 system is octal.

Option A:
Option A denotes the decimal system, which uses ten symbols from 0 to 9 and therefore has base 10. Decimal does not restrict itself to the range 0 to 7. Thus it cannot be described as a system using only digits 0 to 7.

Option B:
Option B refers to the binary system, which uses only two symbols, 0 and 1. Binary is base 2 and therefore has far fewer symbols than a system that uses eight digits. Hence it does not match the description in the stem.

Option C:
Option C indicates the hexadecimal system that uses digits 0–9 and letters A–F to represent sixteen values. This is a base-16 system, so it definitely does not use just digits 0 to 7. Therefore, hexadecimal cannot be the correct answer.

Option D:
Option D is correct because the octal system is precisely the base-8 system using digits 0 to 7. Each octal digit corresponds neatly to three binary bits, which is why it is used sometimes in computing. This matches the given description exactly.