How to create web interpretator

Hello everyone!

I have a project written on C++. The core of it is a built-in language which allows users to manipulate the system and make some calculations. I need adapt this project to web. Namely, I have to make a web design for command prompt/editor. Users should put their commands and then the core would interpret them and make some calculations.
So I need to develop web design for the editor only and then use C++ libraries to make all calculations.
What instrument is the best in my case?
It should be relatively simple but allow to call and get results from C++ procs.