# API Reference

This chapter documents the functions and data structures that make up
the _NNG_ programming interface.

> [!NOTE]
> Interfaces not documented here are not considered public or stable,
> and they may be removed or altered in incompatible ways at any time.

We have organized the reference material along general functional areas.
They are:

- [Asynchronous I/O](aio/index.md)
- [Asynchronous I/O for Providers](aio_provider/index.md)
- General Utility Functions
- Scalability Protocol Sockets
- Scalability Protocol Contexts
- Concurrency / Multi-threading
- HTTP Server
- HTTP Client
- Streaming API
- Statistics API
- Legacy Compatibility