What does an application programming interface (API) do?

An application programming interface (API) is a set of rules and protocols for building and interacting with software applications. The primary function of an API is to facilitate communication between different software systems or components, allowing them to share data and functionalities seamlessly.

In the context of GIS, an API plays a crucial role in moving data between systems, enabling a variety of applications to access geographical data or GIS services. This data transfer capability promotes data reuse, as developers can use these APIs to integrate mapping capabilities or geospatial data into their own applications without needing to build extensive back-end systems from scratch.

The other options, while related to data handling or GIS processes, do not accurately describe the fundamental purpose of an API. For instance, storing large datasets pertains to database management rather than the function of an API, calculating raster values is a specific analytical function that may happen within GIS software but is not the role of an API, and creating user interfaces is a part of software design unrelated to the standard definition of an API.