Railways Notes / Computer Awareness / Chapter 19
Chapter 19 of 33

Computer Number System

The four number systems computers use to represent data — binary, octal, decimal, and hexadecimal.

📖 ~4 min read 💻 RRB NTPC / Group D — Computer Awareness

The Four Number Systems

SystemBaseDigits Used
Binary20, 1
Octal80-7
Decimal100-9
Hexadecimal160-9, A-F

Why Computers Use Binary

Computers use binary (base 2) because electronic circuits have two natural states: ON (1) and OFF (0) — this maps directly to transistor switching.
💡 Example: Decimal 10 = Binary 1010 = Octal 12 = Hexadecimal A

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