Part 1 of the Schneiderware DIY series from Peter Richter released by german magazine CPC Schneider International contained some theoretical background on the DIY projects that followed in the next issues.
The introduction explained basic questions - like "what is a data bus? what is an addresss bus? what are control signals? what are AND and OR gates?" and so on.
- Schneiderware 1 - Intro.pdf - Theory - 6/1986 page 62-67, plus preface from 5/1986 page 21, final notes from 11/1987 page 97-99
About the Schneiderware Series
Whilst the series was aimed at beginners, the DIY schematics could have been a bit less cryptic: They often only showed only low-level details like "Pin 123 wired to Pin4 of IC6" - some additional comments with signal & chip names would have made it much easier to see that, for example, "/IOREQ is wired to an OR gate". One could eventually extract that info from other sections of the article, and, when doing that, one may have really learned something.
Some articles also contained barely described jumpers, undocumented I/O addresses, and example programs in machine code (as hex dumps since printing the complete source code would require more pages), which meant that one needed to do some reverse engineering to understand the software and hardware. For some projects, the source code was released on the magazines Databoxes that could be purchased optionally (instead of entering the type-in listings).