Tight Language Interoperability

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The core of the .NET Framework is the common language runtime. Tight language interoperability is what "common language" means. The real language of the common language runtime is MSIL, a stack-based intermediate language. C#, VB, managed C++, and all other .NET languages compile to MSIL instead of native machine code.

NOTE

For a list of other source code languages and compilers that support the .NET Framework, see http://msdn.microsoft.com/vstudio/ partners /language/default.asp.

MSIL was designed to be generally language agnostic . However, some computer languages have notions that other languages do not understand. For instance, unsigned integers are not supported by all languages. To get around this problem, the .NET Framework defined the common language specification (also known as the CLS).

The CLS rules define what all .NET languages have to support, and it provides for two levels of support ”consumers and producers. All .NET languages must be CLS consumers. That is, they must be able to understand and use assemblies produced by other languages. CLS producers must be able to emit assemblies that conform to all CLS rules. Not all .NET languages are required to be CLS producers .

NOTE

CLS rules cover numerous language features such as naming and use of pointers, arrays, and exceptions. For a list of full CLS compliance rules, see the .NET Framework SDK at http://msdn.microsoft.com/net.

When CLS compliance is guaranteed , .NET languages can inherit from and use classes from other languages. Using special calling conventions or code packaging, language interoperability in the past was generally limited to modules written in other languages. Allowing inheritance between languages is relatively new to mainstream software design.

The language interoperability benefits of the .NET Framework provide a lot of potential for programmers and organizations. Features provided by development environments should no longer be locked into one programming language such as VB or Java. Languages such as COBOL that have "gone out of style" are not obsolete. It is easier to adjust existing code bases written in different languages to use the .NET Framework than it is to completely rewrite them in a different language.

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