Humans seem to have a need to do things that aren’t practical. Make the biggest ball of twine. Engrave the Declaration of Independence on a grain of rice. We want to make things bigger, smaller, faster, or whatever. That might explain why [nanochess] put out bootBASIC.
The 8088 (or later) assembly code gives you a very restricted BASIC interpreter that you can boot up. That means it has to fit in the 512-byte boot block that the hardware loads to get an operating system running. How restricted? Keep in mind it fits in 512 bytes. Each line can only have 19 characters or less. Backspace works, but doesn’t update the screen. Line numbers range from 1 to 999 and there are only 26 integer variables named a through z that hold 16 bits. All statements are in lower case.
While that’s pretty draconian, it still isn’t bad for less than 1K of space. Not only are the four common math operators available, but they obey standard precedence rules (that is, multiply and divide before add and subtract). You can even use parenthesis.
This isn’t going to replace VisualBasic or anything else, of course. But that really isn’t the point. It looks like [nanochess] is using this to promote a book about developing for the boot sector, but that’s not something everyone needs to know how to do. The readme implies the code comments are only in the book, but we glanced through the code on GitHub and it seemed well commented if you are interested in learning a little assembly language.