|"csharp is not recognised as internal or external command operable program or batch file"|
I'm not surprised. Csharp is a programming language which is part of Microsoft Visual Studio. It is usually written C#, the '#' being the musical notion for a sharp key. What that has to do with programming I have no idea, but that's Microsoft for you.
To write any programme all you need is a text editor. Once you have your code written you then need a compiler or an interpreter to turn your code into something the computer can understand.
The only interpreter built into the Cmd prompt is for batch files. To write a programme in Java you need either a Java interpreter or compiler.