Four-valued logic

Four-valued logic, also known as "many-valued logic," is a type of logical system that extends traditional two-valued logic (true and false) by introducing additional truth values. In four-valued logic, the four truth values are typically represented as: 1. **True (T)** 2. **False (F)** 3. **Unknown (U)** or **Indeterminate**, which represents a state where the truth value is not known.