Prolog interpreter with OO extensions - implemented in C++, started in 1992 (my first C++ program). Based on simple algorithm ABC, now ported to 64 bit (just to be used as test case for github publishing).
Originally hosted in MFC based IDE, now survive just the console part. See mini_console.pro Qt project for a simple way to start the REPL.
The interpreter is structured as independent engines, each with a separate memory space.