Basics

Introduction to .NET

The platform (ecosystem) for building anything.

• Software Development Framework: .NET is a platform developed by Microsoft that provides a comprehensive environment for building, deploying, and running applications across various platforms, including web, desktop, mobile, and cloud.

• Cross-platform: It supports multiple operating systems, including Windows, Linux, and macOS, allowing developers to create applications that can run on different environments.

• Multi-language Support: .NET supports several programming languages such as C#, F#, and VB.NET, giving developers flexibility in choosing the language best suited for their projects.

• Unified Programming Model: It offers a unified API for different application types, whether you're developing a web application (ASP.NET), desktop application (Windows Forms or WPF), or cloud services.

• Strong Ecosystem: .NET has a rich ecosystem of libraries, tools, and frameworks, along with strong support for modern software practices such as dependency injection, asynchronous programming, and testing.

Common Language Runtime (CLR)

Converts the program into native code. It acts as an interface between the framework and operating system. It does exception handling, memory management, and garbage collection. 

Source Code Compile --> Intermediate Language (IL) --> CLR load & JIT compiles --> Execute of native code

• Memory Mangement

• Code Access security

• Garbage Collection

• JIT Compilation

• Thread Support

• Debug Engine

• Exception Handling 

Framework Class Library (FCL)

Consisting of a vast collection of reusable, object-oriented classes, interfaces, and value types. Contains thousands of classes to access Windows APIs and common functions like string manipulations, Data structures, stream, IO, thread, security, etc.

Just in Time Compilers (JIT)

It compiles IL code into native executable code (exe or dlls). Once the code is converted to IL then it can be called again by JIT instead of recompiling that code.

Summary 

.NET Framework is the overarching platform that provides the entire ecosystem for application development.

CLR is the runtime component within the .NET Framework that executes the code.

FCL is the class library within the .NET Framework that provides reusable classes and functions to simplify programming tasks.