Very much looking forward to this series. I'm especially interested in where IGS sits technically in relation to other early approaches to visual representation languages like NAPLPS, ReGIS, VT36, and various ANSI expansions, etc. Back when data transmission was glacially slow and memory astronomically expensive, transmitting visual information as the instructions to re-draw it locally was so clearly the right idea, I think almost every major 8-bit and 16-bit platform had disparate hobbyist efforts to implement some form of this. Of course, due to platform fragmentation virtually none gained enough adoption to leave any lasting legacy.
While largely forgotten today, these were the primordial ancestors of the more advanced implementations that would go on to change the world, from Postscript, X11 and Flash to OpenGL and, of course, HTML and CSS.
Code for some of its commands is fairly readable, but others (particularly the `&` Loop command) can be nearly inscrutable.
Though presumably v.44 protocols would compress ANSI graphics text reasonably well?