In a state machine diagram, which statement is true about events?

In a state machine diagram, which statement is true about events?

• A. They define a type of occurrence that can trigger a behavior within an operational system
• B. They define the sequence of states
• C. They store data used by transitions
• D. They signal the end of operation

Answer: (A)

Events are occurrences that can trigger transitions between states in a state machine diagram. This captures the idea that behavior in the system is driven when something happens—like a user action, a message arrival, or a timer firing. Transitions are typically labeled with the event that triggers them, sometimes along with a guard condition and an action to execute. Why this is the best fit: the essence of a state machine is to describe how the system moves from one state to another in response to events. An event represents what must occur to cause that movement, enabling the system to respond dynamically to changing conditions. It’s helpful to contrast with the other notions. A sequence of states is defined by how transitions link states, not by the events alone. Data stored or used by the system reside in variables or attributes, not in the events themselves. And signaling the end of operation is indicated by reaching a final state, not by the event concept itself.

Events are occurrences that can trigger transitions between states in a state machine diagram. This captures the idea that behavior in the system is driven when something happens—like a user action, a message arrival, or a timer firing. Transitions are typically labeled with the event that triggers them, sometimes along with a guard condition and an action to execute.

Why this is the best fit: the essence of a state machine is to describe how the system moves from one state to another in response to events. An event represents what must occur to cause that movement, enabling the system to respond dynamically to changing conditions.

It’s helpful to contrast with the other notions. A sequence of states is defined by how transitions link states, not by the events alone. Data stored or used by the system reside in variables or attributes, not in the events themselves. And signaling the end of operation is indicated by reaching a final state, not by the event concept itself.