that introduced improved performance, better multicore support, and background garbage collection to help apps run smoother Why You Should Be Wary of ".rar" Files When you see the framework offered as a file on file-sharing sites, proceed with extreme caution. Download .NET Framework 4.0
The number is the specific build version for the initial release of .NET Framework 4 .
Building a "deep" blog post about net framework 4.0.30319.rar