Consider a simple vending machine that can be in one of three states: "Idle," "Dispensing," or "Out of Stock." The vending machine transitions between these states based on the insertion of money and the selection of an item. The state transition diagram for this vending machine is shown below.
State Transition Diagram:


Which of the following sequences of events will result in the vending machine transitioning from the "Idle" state to the "Out of Stock" state?

Correct option is E

The correct answer is (e) Insert Money → Select Item. This sequence transitions the vending machine from the Idle state to the Dispensing state and then to the Out of Stock state, as shown in the diagram.
Important Key Points:
1. State Transition Flow: The vending machine starts in the Idle state. Upon inserting money, it moves to the Dispensing state. Once an item is selected, the machine transitions to Out of Stock.
2. The machine reaches the Out of Stock state after an item is dispensed if no further items are available, indicating that it can no longer serve requests until restocked.
Knowledge Booster:
· Restock Event: When the machine is in the Out of Stock state, the Restock event transitions it back to the Idle state, indicating that items have been replenished.
· Incorrect Sequences:
· Insert Money → Select Item → Restock: This sequence returns the machine to the Idle state after restocking, without remaining in the Out of Stock state.
· Insert Money → Select Item → Insert Money: Once the machine is in the Out of Stock state, inserting money will not change its state until restocked.
· Insert Money → Select Item → Select Item: After selecting an item and reaching the Out of Stock state, a second "Select Item" action is not possible.
· Select Item → Insert Money → Select Item: The sequence is incorrect as the machine must be in the Idle state before money is inserted.