Days 22-23 and I worked through getting "Hello World" on the screen using the code from page 81. Part of the reason it took so long to figure out was fighting the environment (both the Devpac Assembler and my understanding of what was supposed to happen). But I finally figured …

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 …

Day 19 and it's time for bitwise arithmetic. I've had many years to learn this, but I love the way Toni Baker addresses what can be a rather challenging topic. Instead of trying to teach decimal to / from binary conversions she instead opts to tackle this with binary and hex …

Day 18 and I played with the looping / comparison in Z80 machine code on the ZX Spectrum. I did the exercise of popping 50 numbers on the stack (reduced to 3 as I didn't want to wait while single-stepping though 50 numbers). Here's the results of my assembly code:

Pretty …

Day 17 started with me looking into the heart of the machine with the jump instructions JP and JR. JP takes a two-byte address and jumps directly to that address. JR is the equivalent, but instead of taking an address it takes a (signed ) byte to jump relative to the …