In 2018 we have 50 Years of Forth. When I looked for a new project for an eBook I realized that one area is not very well covered: How do the Forth internals work?How can you build a Minimal Processor executing Forth directly?How do you write an Assembler in Forth?When I looked around for some documentation, I remembered this series of articles again. They seems to fit very well together.I contacted Brad and asked for permission to publish them as part of the Forth Bookshelf.He liked the idea so I started formatting. I did not change any of the original material.The only part I added was an appendix, where I redid some of the pictures, so I could understand them better.As in many cases, additional material can be found on the Forth-eV.de Wiki, and we will start with the appendix added here, and what else we might come up.I have to thank Brad Ridriguez for the copyright to publish this documentation.Enjoy reading and any feedback please send to [email protected] Brad: Everyone in the Forth community talks about how easy it is to port Forth to a new CPU. But like many "easy" and "obvious" tasks, not much is written on how to do it! So, when Bill Kibler suggested this topic for an article, I decided to break with the great oral tradition of Forthwrights, and document the process in black and white. Over the course of these articles I will develop Forths for the 6809, 8051, and Z80. I'm doing the 6809 to illustrate an easy and conventional Forth model; plus, I've already published a 6809 assembler [ROD91, ROD92], and I'll be needing a 6809 Forth for future TCJ projects. I'm doing the 8051 Forth for a University project, but it also illustrates some rather different design decisions. The Z80 Forth is for all the CP/M readers of TCJ, and for some friends with TRS-80s gathering dust.