The .NET Framework - CLR and Managed Code

The Common Language Runtime is responsible for executing applications and runtime services such as language integration, security enforcement, memory management, and thread execution. The CLR provides metadata, which is a consistent method for describing code.

The Common Language Specification (CLS) and the Common Type System (CTS), fundamental parts of the CLR, define the types and syntax that can be used with many .NET languages. The CTS is a standard that defines how CLR represents and manages types. The CLS is a subset of the features that programming languages must support in order to execute in the context of CLR.
 
The code that executes under control of CLR, such as C#, is called managed code, while the code that executes without requiring CLR, such as C++, is called unmanaged code. Prior to Visual Studio .NET 2002, all applications used unmanaged code. Applications such as MFC, ATL, and Win32 are unmanaged applications. When you are using managed code, the .NET Framework handles any interaction with the operating system, and you just concentrate on the application itself.

The .NET Framework - CLR and Managed Code

Server-side Programming

• Server Side Programming can store and execute program on Web server, link from Web page
• more complex, requires server privileges, but can still be (mostly) secure
• Common Gateway Interface (CGI) programming
• programs can be written to conform to the CGI
• when a Web page submits, data from the page is sent as input to the CGI program
• CGI program executes on server, sends its results back to browser as a Web page
• good if computation is large/complex or requires access to private data
• see http://hoohoo.ncsa.uiuc.edu/cgi/
• Active Server Pages (ASP), Java Servlets, PHP, Server Side Includes, Ajax
• some of these are vendor-specific alternatives to CGI (such as ASP)
• provide many of the same capabilities but using HTML-like tags
• some of these technologies might require functionality to be enabled in the client’s browser (e.g. Ajax generally requires the use of Javascript)

Server-side Programming

Client-Side Programming

• JavaScript
• a scripting language for Web pages, developed by Netscape in 1995
• uses a C++/Java-like syntax, so familiar to programmers, but simpler
• good for adding dynamic features to Web page, controlling forms and GUI
• requires users to have this technology enabled on their browsers
• see http://www.w3schools.com/js/

• Java applets
• can define small, special-purpose programs in Java called applets
• provides full expressive power of Java (but more overhead)
• good for more complex tasks or data heavy tasks, such as graphics
• see http://java.sun.com/applets/

Client-Side Programming