Why CLS ?

CLS is responsible to provide language interoperability

• This is achieved in 2 ways 1) Managed Code 2)Unmanaged code 

Language Interoperability

• Providing code execution support that has been written in other programming language interoperability
• Language Interoperability is achieved using Managed and Unmanaged

Managed Code

• Code for which MSIL is generated after Language Compiler Compilation is directly executed by  the CLR, known as managed code

• The code execution process is known as managed code execution

• CLR will provide all the facilities and features of .Net to the Managed Code Execution like Language Interoperability, Automatic Memory Management, Common Data Type System, Exception Handling Mechanism, Code Access Security etc

Unmanaged Code

• Code that has written before development of .Net for which MSIL is not available is not executed by the CLR directly, rather CLR redirects the code to OS for Execution, which is known as unmanaged code

• The code execution process is known as Unmanaged code execution

• CLR does not provide any facilities and features of .Net to the Unmanaged Code Execution like Language Interoperability, Automatic Memory Management, Common Data Type System, Exception Handling Mechanism, Code Access Security etc

• Examples for Unmanaged Code are COM Components, Win32APIs etc