What is a IL? What is MSIL or CIL , What is JIT? Dot Net Interview Questions.

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(IL)Intermediate Language is also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code is compiled to IL. This IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In- Time (JIT) compiler.

(B)What is a CLR?

Full form of CLR is Common Language Runtime and it forms the heart of the .NET framework.All Languages have runtime and its the responsibility of the runtime to take care of the code execution of the program.For example VC++ has MSCRT40.DLL,VB6 has MSVBVM60.DLL , Java has Java Virtual Machine etc. Similarly .NET has CLR.Following are the responsibilities of CLR

1. Garbage Collection :- CLR automatically manages memory thus eliminating memory leakes. When objects are not referred GC automatically releases those memory thus providing efficient memory management.

2.  Code Access Security :- CAS grants rights to program depending on the security configuration of the machine.Example the program has rights to edit or create a new file but the security configuration of machine does not allow the program to delete a file.CAS will take care that the code runs under the environment of

machines security configuration

3. Code Verification :- This ensures proper code execution and type safety while the code runs.It prevents the source code to perform illegal operation such as accessing invalid memory locations etc.

4. IL( Intermediate language )-to-native translators and optimizer’s :- CLR uses JIT and compiles the IL code to machine code and then executes. CLR also determines depending on platform what is optimized way of running the IL code.

B)What is a CTS?
In order that two language communicate smoothly CLR has CTS (Common Type System).Example in VB you have “Integer” and in C++ you have “long” these datatypes are not compatible so the interfacing between them is very complicated. In order that two different languages can communicate Microsoft introduced Common Type System. So “Integer” datatype in VB6 and “int” datatype in C++ will convert it to System.int32 which is datatype of CTS.CLS which is covered in the coming
question is subset of CTS.

If you have undergone COM programming period interfacing VB6 application with VC++ application was a real pain as the datatype of both languages did not have a common ground where they can come and interface , by having CTS interfacing is smooth.