2.3 Language Concepts and the CLR

2.3 Language Concepts and the CLR

Managed code runs with the constant maintenance of the Common Language Runtime. The CLR provides memory management, type management, security and threading. In this respect, the CLR is a runtime environment. However, unlike typical runtime environments, managed code is not tied to any particular programming language.

You have most likely heard of C# (pronounced See-Sharp). C# is a new programming language built specifically to write managed software targeting the .NET Framework. However, C# is by no means the only language that you can use to write managed code. In fact, any compiler developer can choose to make their compiler generate managed code. The only requirement is that their compiler emits an executable comprised of valid IL and metadata.

At this time Microsoft is shipping five language compilers/assemblers with the .NET Framework. These are C#, Visual Basic, C++, Java Script, and IL. (Yes, you can write managed code directly in IL, however this will be as uncommon as it is to write assembly language programs today). In addition to the five languages shipping with the framework, Microsoft will release a Java compiler that generates managed applications that run on the CLR.

In addition to Microsoft’s language compilers, third parties are producing language compilers for over 20 computer languages, all targeting the .NET Framework. You will be able write managed applications in your favorite languages including Eiffel, PERL, COBOL and Java amongst others.

Language agnosticism is really cool. Your PERL scripts will now be able to take advantage of the same object libraries that you use in your C# applications. Meanwhile, your friends and coworkers will be able to use your reusable components whether or not they are using the same programming language as you. This division of runtime engine, API (Application Programmer Interface), and language syntax is a real win for developers.

The CLR does not need to know (nor will it ever know) anything about any computer language other than IL. All managed software is compiled down to IL instructions and metadata. These are the only things that the CLR deals with. The reason this is important is because it makes any computer language an equal citizen from the point of view of the CLR. By the time JIT compilation occurs your program is nothing but logic and metadata.

IL itself is geared towards object oriented languages. However, compilers for procedural or scripted languages can easily produce IL to represent their logic.