Common Intermediate Language (CIL)

Unlike the C and C++ compilers which compile source code down to the machine code understood by the target microprocessor, the C# compiler compiles to an intermediate byte code format known as the Common Intermediate Language (CIL). This code can, in theory, be taken to any system where there is a CLI compliant Virtual Execution System (VES) and executed. There is, therefore, no need to compile an application for each and every target platform.

The word Common in Common Intermediate Language is used because this format is common to more than just the C# programming language. In fact any programming language may target the CIL allowing libraries and code modules from different languages to execute together in the same application. Typical languages for which CIL compilation is available include Visual Basic, COBOL, SmallTalk and C++.