Inspecting the CLR

The CLR is the core of the .NET Framework. It provides key runtime services to managed code (code written for the CLR), such as memory allocation, garbage collection, security, verification, class loading, just-in-time (JIT) compilation, and so on. The CLR execution model is similar to that of a Virtual Machine. Applications written in .NET-supported programming languages are compiled into an intermediate programming language, Microsoft Intermediate Language (MSIL), which is then JIT compiled to actual machine code on execution.

Key components of the CLR are shown in Figure 2.1. They include the following:

• Verifier verifies whether all executing code is type safe and contains well- formed metadata.

• Class loader is responsible for finding and loading .NET classes.

• The JIT compiler converts IL code into native code for execution on a target operating system. Because the compilation process is done at the execution time, it can be optimized for the target machine processor and its instruction set.

• Because the JIT compiler is used to create an actual executable for the underlying platform, a .NET application can execute on multiple platforms ”from a desktop or workstation to PDA and Smartphone devices to a full-blown enterprise server ( illustrated in Figure 2.2).

  Figure 2.2. .NET applications on many platforms.

  

• Garbage collector provides automatic management of .NET objects, detecting nonreferenced objects.

Figure 2.1. Key components of the CLR.

.NET COMPACT FRAMEWORK

.NET Compact Framework is a subset of the .NET Framework class library, which runs .NET applications on a large set of mobile devices, including PDAs and Smartphones.