ASP (Active Server Pages) and ASP.NET are web-programming applications used to create web pages. Both programs were developed by Microsoft and can only function on a Microsoft Operating System, like Windows 7, Windows Vista, Windows XP Pro or Windows XP Home Edition. Unfortunately, this web programming software is not compatible with any other operating system. They also have some major differences.
The classic ASP version is Microsoft ‘s first version of server side scripting. It is used to create dynamic web pages that are saved with the .asp extension. ASP.NET files on the other hand are saved with the .aspx extension.
One of the major differences though, between ASP and ASP.NET is the compatibility with other programming languages. In ASP you are limited to Visual Basic Script (VB Script) or JavaScript. ASP only interprets them, but not compile them. With ASP.NET you can work with and compile CLR (Common Language Runtime) Computer Languages found on the .NET framework. These languages include C#(sharp), F#(sharp), Visual Basic.NET, and C++, but it does not support VBScript like ASP. Instead, it supports VB.NET (Visual Basic.NET).
Another difference is in the programming. In ASP, the code is written in a single file but in ASP.NET there are 2 parts, the aspx file, where html codes are written, and then there is the aspx.vb file where all the programming is done.
Code execution also operates differently. In ASP, code is executed from the top to the bottom, using functions, sub routines, and classes. ASP.NET though, executes code, using OOP (Object Oriented Programming) where an event driven model is used to execute events using mouse clicks or page loads.
ASP and ASP.NET operates under the IIS(Internet Information Services) for Windows Server, but ASP uses the inetinfo.exe option whereas ASP.NET uses the aspnet_wp.exe option.
These major differences are just a few to help you differentiate between the two and help you simply understand how they function. It is also important to note that ASP.NET is pretty much an upgrade of ASP, with additional features. Even though there are differences, as long as you understand the concepts of ASP, you will be able to easily transition to ASP.NET.
Chiranjiv ‘The Hustler” Choudhary, Differences between ASP.NET and ASP, Code Project