Reverse engineering Microsoft BASIC
This video is a bit of a continuation from my last video. At the end of the last video, I mentioned wanting to be able to print a string to the LCD using a single BASIC instruction. That required figuring out how to extract a string (or other expression). Not knowing much about the way BASIC worked under the hood, I looked at the PRINT instruction to see how it works and figured things out from there. This video walks through what I learned.
As always, let me know if you see anything that's overly confusing or wrong. And thanks as always for your continued support!
-Ben
Comments (11)
One question; one request: Q: did MSFT Basic originally have only a char/string and a float data type where integers were stuck with the overhead thus limiting the # of digits? Request: Would love to see a video on how the expression evaluation function works. It had to capably support nesting and paren evaluation not to mention a fair amount of math vs. logic (embedding formula to evaluate to boolean for if/thens). This has always been a mystery to me. Good sleuthing thus far.
Top notch like always! Love your videos, they are super inspiring and interesting!
Another fantastic video. Really interesting.
Thanks for the video. Watching this makes me wonder what happens when you hit data type limits, say trying to use a string > 256 bytes.
Same for the numerical values. This is presumably not IEEE 754 floating point but something custom. How does it work and what is the supported range?
Hi Ben, yet another nice video, just one question popped in my head during watching. What else can be printed with PRINT and immediately numeric variables came on my mind. I suppose it will work, but I sort of miss it in your tests during the video.
Another fine video. Thanks. I would be very interested in a video about how both fixed point and floating point work. Thanks again.
If it's not too much bother, would you mind adding the youtube video URL in your post? When I tap the video from the patreon app it redirects to a barren "login to youtube to prove you're not a bot" page, preventing me from reaching the "open in youtube app" button.
Here's the direct link: https://youtu.be/mfT4T1pUGSY
Nice one Ben! I'm following along on FPGA. Struggling with UART flow control as the devboard doesn't have HW flow control pins connected. Tried XON/XOFF but the FTDI part has too large buffers and it doesn't stop in time! Hoping you interface the video card to the machine!
Did you ever publish the schematic of this version of the computer? I think the one on the website is missing flow control?