共通语言执行平台（Common Language Runtime，简称CLR）是微软为他们的.NET的虚拟机所选用的名称。这是共通语言基础（简称CLI）的微软实现版本，它定义了一个代码执行的环境。CLR执行一种称为微软中继语言的bytecode，这个是微软的共通中继语言实现版本。
CLR执行在微软的窗口操作系统上。查看共通语言基础可以找到该规格的实现版本列表。其中有一些版本是执行在非Windows的操作系统中。
CLR的主要功能如下
基类库支持 Base Class Libray Support
内存管理 Memory Management
线程管理 Thread Management
内存自动回收 Garbage Collection
安全性 Security
型别检查 Type Checker
例外管理 Exceptino Manager
除错管理 Debug Engine
中间码(MSIL)到机器码(Native)编译
类装载 Class Loader
开发人员使用高级编程语言撰写程序。接下来编译器将代码编译成微软的中继语言(MSIL)。执行的时候CLR会将MSIL码转换为操作系统的本地码（Native code）。CLR内置有JITJust In Time）Compiler。
The Common Language Runtime (CLR) is the virtual machine component of Microsoft's .NET initiative. It is Microsoft's implementation of the Common Language Infrastructure (CLI) standard, which defines an execution environment for program code. The CLR runs a form of bytecode called the Common Intermediate Language (CIL, previously known as MSIL -- Microsoft Intermediate Language).
Developers using the CLR write code in a language such as C# or VB.Net. At compile time, a .NET compiler converts such code into CIL code. At runtime, the CLR's just-in-time compiler converts the CIL code into code native to the operating system. Alternatively, the CIL code can be compiled to native code in a separate step prior to runtime. This speeds up all later runs of the software as the CIL-to-native compilation is no longer necessary.
Although some other implementations of the Common Language Infrastructure run on non-Windows operating systems, Microsoft's implementation runs only on Microsoft Windows operating systems.
The virtual machine aspect of the CLR allows programmers to ignore many details of the specific CPU that will execute the program. The CLR also provides other important services, including the following:
Memory management
Thread management
Exception handling
Garbage collection
Security
参考：
(Microsoft MSDN) http://msdn.microsoft.com/en-us/library/ddk909ch(vs.71).aspx
http://en.csharp-online.net/index.php?title=.NET_Common_Language_Runtime_%28CLR%29
