What is the difference between Managed Code and Unmanaged Code?


Unmanaged code is the code that is directly executed by the Operating System. The unmanaged code is architecture specific it can be run only in the machine where it has been complied, the complier transforms the code into the machine language which is then executed, in case it needs to be run in a different machine it needs to be complied again. In unmanaged code the developer needs to take care of the security, memory management etc. Few e.g. are VB 6.0, C++, C etc.

On the other hand the Managed Code is the code that is not targeted directly to the Operating System rather to the Managed Runtime Execution Environment. For the .NET Framework it is known as CLR (Common Language Runtime). When a managed code is complied it is transformed into MSIL (Microsoft Intermediate Language, currently known as CIL (Common Intermediate Language)) and an executable is created and also the meta data is created which describes the characteristics of the methods and properties. The CLI specifies the rules as to how this meta data is exposed. When the executable is run by the user the CLR’s JIT (Just In Time Compiler) complies the MSIL into the native code specific to the underlying architecture.
 
Since the managed code is complied into an intermediate language it is machine independent and takes the services of the managed environment for e.g. security checks, garbage collection, exception handling etc.

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