I wrote an AI Expert article on a similar theme ("Simulating Intelligent Interacting Objects in C", AI Expert, January 1989) about using C for OO programming of

I wrote an AI Expert article on a similar theme ("Simulating Intelligent Interacting Objects in C", AI Expert, January 1989) about using C for OO programming of a robot simulator -- where the first argument is a pointer to a data structure representing the object. I prefixed all the function names with the class name, like Robot_move(robot, x, y). I was inspired by IIRC Eric Schildt's previous article elsewhere on how OO is an attitude. Looks like a very comprehensive book though compared to just some short articles (even if it does not cite those as previous work). In general, this idea of opaque handles was (and is) very common in C programming, like with file operations. So, the question is what conventions we use or what convenience superstructure we build around that basic idea of handles.