What is the exact role of CLR in dot net framework?

Our book Professional .NET Framework 2.0 would be a very good source to answer a question like this:
http://www.wrox.com/WileyCDA/WroxTit...fContents.html

Here's the explanation of the CLR from chapter 1 of that book, which you can read along with 200 other Wrox books as part of a wrox.books24x7.com subscription:

First, the Common Language Runtime (CLR) is the virtual execution environment — sometimes called a virtual machine — that is responsible for executing managed code. Managed code is any code written in a high-level language such as C#, Visual Basic, C++/CLI, IronPython, and the like, which is compiled into the CLR's binary format, an assembly, and which represents its executable portion using Intermediate Language (IL). Assemblies contain self-descriptive program metadata and instructions that conform to the CLR's type system specification. The CLR then takes this metadata and IL, and compiles it into executable code. This code contains hooks into CLR services and Win32, and ultimately ends up as the native instruction set for the machine being run on. This happens through a process called just-in-time (JIT) compilation. The result of that can finally be run.



Jim Minatel
Acquisitions Director
Wiley Technology Publishing
WROX Press
Blog: http://wroxblog.typepad.com/
Wrox online library: http://wrox.books24x7.com

What about Visual Studio IDE? Is it having built in CLR? When we build the solution, we can execute the application. How does it happen?

Visual Studio is presumably built in .NET. It runs on the CLR. The CLR is not built into Visual Studio. When you "run" a program in Visual Studio, you are really compiling the application using msbuild, starting the program in its own process and attaching the Visual Studio debugger to that process.

-Peter