CLI, CLR, MSIL, JIT, .NET, C#, CLS and CTS ....

To most .NET programmers, there will be nothing new in this particular post. But, it only seems fitting that the initial post to this blog should be this simplified overview, just to make sure we're all on the same page.

The Common Language Infrastructure (CLI) is an international standard defined in ECMA-335. The CLI specifies the common mechanics for high-level, CLI-compliant programming languages. This standard is neither language specific nor platform specific.

The Common Language Runtime (CLR) is Microsoft's implementation of the CLI standard. The CLR executes a type of bytecode known as the Microsoft Intermediate Language (MSIL). At run-time, that MSIL bytecode is turned into native, executable code by the Just-In-Time compiler (JIT compiler). In theory, any CLI-compliant programming language is supported on any platform with the appropriate compiler and runtime.

The term ".NET" refers to a Microsoft product that includes the CLR, JIT compiler, source code compilers, and an entire framework of CLI-compliant components targetted for the Windows platform.

C# is a CLI-compliant programming language defined by the C# Language Specification (C#LS) known as ECMA-334. C#.NET is Microsoft's implementation of the C#LS for use with the Microsoft CLR, JIT compiler and framework components on Windows platforms. Since C#.NET is the only real implementation of the C# programming language (aside from the Mono open source project), the terms "C#" and "C#.NET" are often used interchangeably.

There are several .NET languages, including C#.NET and VB.NET. Even though both of those languages are CLI-compliant, the languages themselves have different capabilities. The Common Language Specification (CLS) is a Microsoft specification that defines the guaranteed subset of common functionality that is useable by all .NET programming languages. For example, the CLS defines the Common Type System (CTS), and the CTS does not include unsigned integers because the VB.NET programming language does not support unsigned integers.