.NET Runtime and Libraries

.NET (formerly .NET Core) is a free, open-source, cross-platform development platform created by Microsoft. Originally launched as .NET Core 1.0 in June 2016 (led by Scott Hunter, Immo Landwerth, and the Microsoft .NET team) as a complete rewrite of the proprietary .NET Framework, .NET unifies the platform under a single runtime that runs on Linux, macOS, and Windows. The current version is .NET 9 (released November 2024). Key features: runtime: CoreCLR is the core execution engine (JIT compiler via RyuJIT, garbage collector, type system, exception handling). CoreRT/NativeAOT compiles .NET assemblies ahead-of-time to native machine code, eliminating the JIT at runtime. Mono runtime for mobile and WebAssembly targets. Base Class Library (BCL): the foundational libraries providing collections, file I/O, networking, threading, cryptography, JSON, XML, HTTP, and more. The BCL is shared across all .NET implementations. C#: the primary language for .NET. C# 13 (2024) adds features like params collections, lock statement improvements, and escape character. F#: functional-first language. VB.NET: legacy support. CLR features: generational garbage collector (Gen 0, Gen 1, Gen 2) with background GC for low-latency server scenarios, SIMD acceleration via System.Numerics, hardware intrinsics. Performance: tiered compilation (JIT methods at two optimization levels), dynamic PGO (profile-guided optimization), crossgen2 for ready-to-run images. Cross-platform: Linux (x64, ARM64), macOS (x64, ARM64/Apple Silicon), Windows (x64, x86, ARM64). Container support: optimized for Docker and Kubernetes with minimal base images. ASP.NET Core for web apps and APIs. Entity Framework Core for data access. ML.NET for machine learning. C#. MIT.