This document discusses different number systems used in digital techniques. It defines analog and digital signals, with analog having continuous values and digital having a finite set of discrete values. Four main number systems are covered: decimal with base 10, binary with base 2, octal with base 8, and hexadecimal with base 16. Each system's base, symbols used, examples of representations, and how place values determine a number's value are explained. The document aims to introduce students to number systems and their applications in digital contexts.