What are system APIs used for?

System APIs are designed to allow developers to interact with the operating system in a structured and efficient way. They provide a set of routines, protocols, and tools that enable software applications to communicate with the underlying OS, perform tasks like file management, memory allocation, and process control, and utilize system resources effectively. By using system APIs, developers can access the functionality needed to build applications without having to manipulate the hardware directly, which simplifies the development process and enhances software compatibility across various hardware configurations.

While the other options touch on important aspects of computer systems, they do not encapsulate the primary function of system APIs. User interface designs are more related to UI frameworks rather than APIs. Managing hardware components often involves lower-level programming, in contrast to the higher-level abstractions provided by system APIs. Securing network connections, while an important function, typically relies on other types of services or protocols rather than being strictly a function of the system APIs themselves.