| > What popular languages fall into this category ? Not all, but many. Going down the list of most popular languages from https://www.tiobe.com/tiobe-index/ - Python - CPython, PyPy, MicroPython C - numerous (gcc, clang, msvc, tcc, etc.) Java - https://en.wikipedia.org/wiki/List_of_Java_virtual_machines C++ - gcc, clang, msvc, etc. C# - Microsoft's version and mono Visual Basic - probably only one implementation JavaScript - https://notes.eatonphil.com/javascript-implementations.html SQL - assorted dialects, not sure that counts PHP - probably only one implementation ASM - assorted dialects, not sure that counts Classic Visual Basic - probably only one implementation Go - only one version that matters, AFAIK MATLAB - probably only one implementation R - probably only one implementation Groovy - probably only one implementation Ruby - https://opensourcelibs.com/lib/ruby-implementations (Why are there so many in Go?) Swift - probably only one implementation Fortran - https://fortran-lang.org/compilers/ Perl - probably only one implementation Delphi/Object Pascal - there are a decent number of Pascals historically, and FPC and Delphi are the big modern options |