I learned BASIC in 1981 on the TRS-80 Model I with 4k RAM (later upgraded to a massive 16k), and it wasn't long before someone showed me EDTASM [1], and I was hooked. My parents couldn't believe me when I asked them to buy "How to Program the Z80" by Rodnay Zaks [2]. They were shocked, it was the first time I asked them to buy a technical book. I was so excited I couldn't sleep for days. I was in High School, and I would carry the book around and read, use the lookup tables, and write Z80 assembly in my spiral-bound 8.5"x11" notebook.

One three-day weekend, I slept about 4 hours while I was disassembling the BASIC ROM to find nuggets I could call in my Z80 programs, and also to learn so much more about the video, the cassette interface, interrupts, etc. My notebook looked like something a madman had scribbled on the walls of an asylum to everyone around me, but to me it was perfectly organized, and I used it to reference things I would use later in my programs. I got to the point where I could read the hex dumps and "see" the op codes in my mind; people would look over my shoulder while I was debugging, and I'd be explaining what the code was doing, but I hadn't disassembled it yet. I didn't even realize I was doing that until one of my classmates pointed it out: "Hey, disassemble that. I'm not following you, how the heck do you see that?"

And all of this because my science teacher had that TRS-80 Model I sitting in the corner of his classroom gathering dust; nobody knew what it was, I didn't either, but I had to figure it out. I've always had this bug, I don't believe in magic, I want to know how everything works, it's been an insatiable thing all my life, that first machine set me on a course of learning for the rest of my life.

Thanks, Mr. Kruzan, you changed my life. I'll never forget you. Oh, and thanks to all the people who created the Z80, the TRS-80 Model I, and paved the path for me to learn computers and never stop learning.

We are truly building on the shoulders of giants; every generation, more giants. It's humbling to look back and think about it forty-five years later...

[1] https://www.trs-80.org/edtasm.html

[2] http://www.z80.info/zip/zaks_book.pdf

PS: Pretty sure the memcpy examples have a stack bug.