Render advanced 3D graphics and perform data-parallel computations. Get fine-grained access to the GPU while minimizing CPU overhead. The Metal Framework provides extremely low-overhead access to the GPU, enabling incredibly high performance for your sophisticated graphics rendering and computational tasks. Metal eliminates many performance bottlenecks—such as costly state validation—that are found in traditional graphics APIs. Metal moves all expensive state translation and compilation operations out of the critical path of your most performance sensitive rendering code. It provides precompiled shaders, state objects, and explicit command scheduling to ensure that your application achieves the highest possible performance and efficiency. Graphics, compute, and blit commands can be used together seamlessly and efficiently. Metal is specifically designed to exploit modern architectural considerations, such as multiprocessing and shared memory, to make it easy to parallelize the creation of GPU commands.

Nanopb - protocol buffers with small code size

Protocol Buffers (a.k.a., protobuf) are Google's language-neutral, platform-neutral, extensible mechanism for serializing structured data.

WebKit provides a set of classes to display web content in windows, and implements browser features such as following links when clicked by the user, managing a back-forward list, and managing a history of pages recently visited.

This document describes the Accelerate framework, which contains C APIs for vector and matrix math, digital signal processing, large number handling, and image processing.

The Address Book framework provides access to a centralized contacts database, called the Address Book database, that stores a user’s contacts. Applications such as Mail and Messages use this database to present information about known and unknown persons.

AFNetworking is a networking library for iOS and Mac OS X. It's built on top of the Foundation URL Loading System, extending the powerful high-level networking abstractions built into Cocoa. It has a modular architecture with well-designed, feature-rich APIs that are a joy to use.