What command is used to trigger or start an event in a program?

The correct term used to start or invoke an event in a program is "broadcast." In programming, particularly in event-driven architectures, broadcasting is the process of sending a signal to all relevant listeners or participants within a system, indicating that a certain event has occurred. This method allows different components of a program to respond to various events efficiently, without the need for direct communication between them.

Broadcasting is often used in scenarios where multiple objects need to react to an event, such as user interactions or changes in data. When an event is broadcasted, it can be caught by any listener that has expressed interest in that specific event type, which facilitates a modular design in applications.

While other terms such as "invoke," "call," and "trigger" may be used in specific contexts in programming, they do not encompass the broad capability of notifying multiple parts of a system simultaneously, as broadcasting does. "Invoke" and "call" typically refer to executing functions or methods, while "trigger" might suggest initiating a process rather than sending out notifications broadly.