As far as I understand all scripting languages and core scientific programs are usually written in C; this renders the implementation messy yet in a way straight to the point.
I understand these people would like to max their performance but is there a real difference between using C strings and C structures to using C++ classes; C++ seems to work the same way, apart from virtual functions, it stores a class function once and every instance of that class calls that one function.
What makes C faster and is it a notable difference in a project such as python or sqlite who have to be the fastest?