.NET Windows Forms in a Nutshell

The Common Language Runtime

The Common Language Runtime (CLR) is the environment in which all programs run in .NET, so it affects everything we do as developers. It is therefore important to understand what it does and what that means to our programs, so we will now look at the most important features of the CLR.

All high-level programming languages have a runtime. This is because an OS process provides a fairly low-level set of features, typically just memory, pointers, threads, machine code, and system calls. The job of any language’s runtime is to bridge the gap between these OS facilities and the constructs defined by the programming language. In C++, the runtime provides such features as exception handling, runtime type information, and the standard C++ library. The Visual Basic runtime includes intrinsic handling for COM and automatic memory management. Traditionally, each language has provided its own runtime, such as MSVCRT.DLL for C++, MSVBVM60.DLL for Visual Basic, and the Java Virtual Machine (MSJAVA.DLL, if you’re using Microsoft’s VM) for Java.

In .NET, there is just one runtime, which is used by all languages, the CLR. The fact that all languages use this one runtime is important for a number of reasons. It means components can easily be written in and used from any language because all languages represent types and objects in the same way. (Anyone familiar with COM in C++ will be amazed at how simple it is to write and use .NET components.) Moreover, it means that ...