I am reading a calculator book again, this time an electronic copy. Pity it's only available in German!
"Programmierbare Taschenrechner - selbst gebaut" does what the title says: it teaches the lost art of building a homebrew programmable pocket calculator.
My German is rusty, but I can still appreciate the value of this book. Starting with the simple (a four-function calculator using only two chips on a breadboard) it demonstrates through progressively more difficult designs how a programmable calculator can be constructed.
I especially like it that the designs are not limited to "cookbook" solutions that only teach the reader how to wire together custom calculator chips. Starting in chapter 4, the author demonstrates a programmable calculator that is implemented in BASIC, using a BASIC Stamp. Now that's what I call a real design! OK, so he doesn't build his own processor using just TTL chips, but this really is the next best thing: through the BASIC code, the logic of the calculator's operation is clearly presented to the interested reader.
I must say I am almost ready to reach for my soldering iron. (A while back, I was thinking about implementing a minimalist programmable calculator using a PIC chip. This is almost like that.)
"Programmierbare Taschenrechner - selbst gebaut" can be obtained online at http://www.elektor.de/products/books/computer/programmierbare-taschenrechner---selbst-gebaut-(e.503602.lynkx. The BASIC Stamp software is downloadable from the same site.