So what is C# or C++ ?
How does it differ to BASIC ?
C# and C++ are a different family of language, both being descendants of the original C language. This means that the syntax and keywords are both totally different than BASIC. The C family of languages let you work at a lower level of the computer hardware than BASIC, say for manipulating the content of memory, or messing about with network connections, and that kind of thing.
C# and C++ are also object oriented languages, which means you create code modules (classes) which model real world entities. E.g. you could have have a Car class that models both the properties of a car (make/model/colour), and actions that a car can take (accelerate/brake/change gear). You've also got fun stuff like inheritance which allows you to build classes on top of each other..
BASIC is more of a procedural language, meaning that you can create procedures (subroutines) to separate out and reuse common sequences of commands. These subroutines can be called from the "main" program to perform individual tasks, and then return control to the main program.
Here's a comparison table of languages for a laugh:
https://en.wikipedia.org/wiki/Comparison_of_programming_languagesI'd say that there's very little commercial development done these days using BASIC, compared to C/C++/Java/C#.