What allows developers to communicate with an application or operating system using a set of universal commands?

The correct answer is Application Programming Interface (API). An API serves as an intermediary that allows different software applications to communicate with one another. It defines a set of rules and protocols for building and interacting with software applications. This means developers can use a standardized set of commands to request specific functionalities or data from an application or operating system without needing to understand its internal workings.

APIs are essential in modern software development, as they allow for the creation of web services, integration between systems, and the use of third-party functionalities within applications. This standardized approach streamlines development and promotes interoperability between different technologies, which is crucial for building complex systems or services.