It's sad that most of these "bootloader" guides don't take you into actualy boot-loading something. No searching a file system. No loading another binary. No setting up 32 mode. Nothing, just printing text. That's what most of these are on.
He uses bios calls , thats what you need to learn to be able to write a bootloader, the rest is just reading up some documentation about what you are going to load. You can't fit a filesystem parser into 1 sector and have anything other sensible in there... from bootloader you load sectors from disk, using bios generally (on x86 atleast). and you can understand how to do it from this tutorial.
That documentation is usually.... lacking
> You can't fit a filesystem parser into 1 sector and have anything other sensible in there
You don't use a single sector. You use a 2 stage bootloader that uses a reserved FAT sector. In FAT12 (at least) you can specifiy how many reserved secotrs on formatting. A reserved sector comes directly after the first sector. You can do a full FAT12 implementation in assembly in two sectors.
> using bios generally (on x86 atleast). and you can understand how to do it from this tutorial.
You're going to need to do a lot more reading. Even just looking up the interrupts you need is a task. I've found nothign that does a good job explaining the 1, 2, and 3s of how to get all the way to booting from a formated disk.