It is mostly written in C or C++. the work is mostly being done in a lower-level programming language like C or Fortran (Of course, since R is open source, you can take a look at the C or Fortran code as well, if you like.)
Disclimer: PCDS.CO.IN not responsible for any content, information, data or any feature of website.
If you are using this website then its your own responsibility to understand the content of the website