UML State Diagram Notation

(1) Rounded rectangle,A system state — a mode the system is in, optionally with an action performed in that state

(2) Labeled arrow between rounded rectangles,A stimulus (event) that causes a transition from one state to another

(3) do: [action] inside a rounded rectangle,An action performed by the system while it is in that state

(4) Filled circle,The start state — where the system begins

(5) Filled circle inside a larger circle,End state — the system has finished processing

Explanation

UML state diagram notation: rounded rectangles = states (may include 'do: action' describing what the system does in that state); labeled arrows = transitions triggered by stimuli/events; filled circle = initial state; filled circle inside larger circle = end state. The labels on arrows represent the stimuli that force a transition.

Symbol	Notation Title	Meaning & Description
	Filled circle	Represents the initial state, marking the default starting point of the system before any transitions occur.
	Rounded rectangles	Represents states that the system can occupy. These blocks may optionally include internal behavior details, such as a do: action label describing the ongoing work the system executes while remaining in that specific state.
	Labeled arrows	Represents transitions between states. The text label on the arrow explicitly indicates the external stimulus or event that triggers and forces the system to move from the source state to the target state.
	Filled circle inside larger circle	Represents the end state (or final state), indicating that the state machine has reached the conclusion of its lifecycle processing loop.