Days 20 and 21 saw me finish up the bitwise operators (RL,, RR, RLC, RRC, SLA, SRA, SRL, and SET). Intersting to see the bredth of shifting and rotating operations, although I'm not 100% clued-in on which ones to use for which occasions. I'm pretty sure they'll become more apparent as I press onward in the book.
The next chapter in Mastering Machine Code on your ZX Spectrum deals with outputting to the screen. The fist example shows how to output an asterisk to the screen. That's about as far as I got for today. From what I gather there are some routines that we'll be using to do proper printing onto the screen in the upcoming sections. Can't wait. :)