【正文】 ations that run on the .NET Framework. You can use C to create traditional Windows client applications, XML Web services, distributed ponents, clientserver applications, database applications, and much, much more. Microsoft Visual C 2020 provides an advanced code editor, convenient user interface designers, integrated debugger, and many other tools to facilitate rapid application development based on version of the C language and the .NET Framework. The Visual C documentation assumes that you have an understanding of basic programming concepts. If you are a plete beginner, you might want to explore Visual C Express Edition, which is available on the Web. You can also take advantage of any of several excellent books and Web resources on C to learn practical programming skills. C syntax is highly expressive, yet with less than 90 keywords, it is also simple and easy to learn. The curlybrace syntax of C will be instantly recognizable to anyone familiar with C, C++ or Java. Developers who know any of these languages are typically able to begin working productively in C within a very short time. C syntax simplifies many of the plexities of C++ while providing powerful features such as nullable value types, enumerations, delegates, anonymous methods and direct memory access, which are not found in Java. C also supports generic methods and types, which provide increased type safety and performance, and iterators, which enable implementers of collection classes to define custom iteration behaviors that are simple to use by client code. As an objectoriented language, C supports the concepts of encapsulation, inheritance and polymorphism. All variables and methods, including the Main method, the application39。s types, version, culture, and security requirements. When the C program is executed, the assembly is loaded into the CLR, which might take various actions based on the information in the manifest. Then, if the security requirements are met, the CLR performs just in time (JIT) pilation to convert the IL code into native machine instructions. The CLR also provides other services related to automatic garbage collection, exception handling, and resource management. Code that is executed by the CLR is sometimes referred to as managed code, in contrast to unmanaged code which is piled into native machine language that targets a specific system. The following diagram illustrates the piletime and run time relationships of C source code files, the base class libraries, assemblies, and the CLR. Language interoperability is a key feature of the .NET Framework. Because the IL code produced by the C piler conforms to the Common Type Specification (CTS), IL code generated from C can interact with code that was generated from the .NET versions of Visual Basic, Visual C++, Visual J, or any of more than 20 other CTSpliant languages. A single assembly may contain multiple modules written in different .NET languages, and the types can reference each other just as if they were written in the same language. In addition to the run time services, the .NET Framework also includes an extensive library of over 4000 classes anized into namespaces that provide a wide variety of useful functionality for everything from file input and output to string manipulation to XML parsing, to Windows Forms controls. The typical C application uses the .NET Framework class library extensively to handle mon plumbing chores. 。 it is a stackallocated type that can implement interfaces but does not support inheritance. In addition to these basic objectoriented principles, C facilitates the development of software ponents through several innovative language constructs, including: method signatures cal