(
J sharp) A programming language from Microsoft based on Java that included most of the features of the discontinued Visual J++ due to litigation from Sun. J# compiled into the Microsoft Intermediate Language (MSIL) for the .NET platform. It supported COM objects and the J/Direct interface to Windows. J# was dropped in Visual Studio 2008.
Why the Number Sign?
Because the # symbol is similar to the sharp music notation symbol. See
.NET Framework,
C# and
F#.