This document discusses four main number systems: binary, octal, decimal, and hexadecimal. It defines key terms like base, bits, bytes, and nibbles. For each number system, it provides the symbols used, the base, and examples of conversions between them. The binary system uses 0 and 1, with a base of 2. Octal uses 0-7 with a base of 8. Decimal uses 0-9 with a base of 10. Hexadecimal uses 0-9 and A-F, with a base of 16. A table compares and contrasts the number systems.