The Digital Antiquarian‘s website contains a wealth of information, but rather than let my works get too gummed up in describing it all right now, here’s is one page from 2012, on the creation of ZIL, the Zork Implementation Language, and the virtual machine that runs it, the Z-Machine.
When we left off last time, Marc Blank and Joel Berez were considering how to bring Zork to the microcomputer. Really, they were trying to solve three interrelated problems. At the risk of being pedantic, let me lay out them for you:
1. How to get Zork, a massive game that consumed 1 MB of memory on the PDP-10, onto their chosen minimum microcomputer system, an Apple II or TRS-80 with 32 K of RAM and a single floppy-disk drive.
2. How to do so in a portable way that would make it as painless as possible to move Zork not only to the Apple II and TRS-80 but also, if all went well, to many more current and future mutually incompatible platforms.
3. How to use the existing MDL source code to Zork as the basis for the new microcomputer version, rather than having to start all over again and implement the game from scratch in some new environment.
The Digital Antiquarian
The Digital Antiquarian: ZIL and the Z-Machine