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 an example conversion. The binary system uses 0 and 1 and has a base of 2. Octal uses 0-7 and has a base of 8. Decimal uses 0-9 and has a base of 10. Hexadecimal uses 0-9 and A-F, with a base of 16. In the last section, it provides a comparison table of the number systems.