This free book is a collection of tutorial notes and sample codes written by the author while he was learning UML (Unified Modeling Language) himself. Topics include UML, Diagram, Notation, Shape, Class, Object, State, Activity, Action. Main tutorials include: Introduction to UML - UML Class Diagrams - UML Activity Diagrams - UML Sequence Diagrams - UML State Machine Diagrams - UML Use Case Diagrams - Using MS Visio to Draw UML Diagram