IL: The Common Language Run time manages the execution of .NET code. Here is how it works: When you compile a C# program, the output of the compiler is not executable code. Instead, it is a file that contains a special type of pseudo-code called Microsoft Intermediate Language (MSIL). MSIL defines a set of portable instructions that  are independent of any specific CPU. In essence, MSIL defines a portable assembly language. One other point: although MSIL is similar in concept to Java’s byte code. CLR to Translate the Intermediate code into Executable code. Thus, any program compiled to MSIL can be run in any environment for which the CLR is implemented.