Microsoft .NET Framework!!

The .NET Framework allows you to : 

• Apply common skills across a variety of devices, application types, and programming tasks.
• Integrated with other tools and technologies to build the right solution with less work.
• Build compelling applications faster.

The .NET Framework is :

• Common Language Runtime - provides an abstraction layer over the operating system.
• Base Class Libraries - pre-built code for common low-level programming tasks.
• Development frameworks and technologies - reusable, customizable solutions for larger programming tasks.  

Download link :

Link : .NET Framework 1.0

Link : .NET Framework 1.1

Link : .NET Framework 2.0

Link : .NET Framework 3.0

Link : .NET Framework 3.5

• Part 1
• Part 2
• Part 3

Link : .NET Framework 4.0