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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 l

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.

gravypod 10y ago
> the rest is just reading up some documentation about what you are going to load 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.
- johnnycarcin 10y ago
  You sound pretty well versed in this area, would you be interested in writing something up? Don't take this as a dig, I know the value of free time and how much that free time is lacking for most of us, I just thought I'd toss it out there.
  - gravypod 10y ago
    The best I can do is load up a second stage. Searching for the COM file is where I get lost. I've also been trying to do it in C for months and I haven't been able to finish for various reasons.
- sigjuice 10y ago
  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. There is unlikely to be a single thorough body of documentation on this sort of thing. IMHO, the best resource would be the numerous open source bootloaders that are available.
- upofadown 10y ago
  There isn't a lot there to document. At this point it counts as a part of our civilization. It's even on Wikipedia: * https://en.wikipedia.org/wiki/Master_boot_record https://en.wikipedia.org/wiki/Master_boot_record * https://en.wikipedia.org/wiki/BIOS_interrupt_call https://en.wikipedia.org/wiki/BIOS_interrupt_call There isn't much call for FAT12 these days...

gravypod 10y ago

> the rest is just reading up some documentation about what you are going to load 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.

johnnycarcin 10y ago
You sound pretty well versed in this area, would you be interested in writing something up? Don't take this as a dig, I know the value of free time and how much that free time is lacking for most of us, I just thought I'd toss it out there.
- gravypod 10y ago
  The best I can do is load up a second stage. Searching for the COM file is where I get lost. I've also been trying to do it in C for months and I haven't been able to finish for various reasons.
sigjuice 10y ago
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. There is unlikely to be a single thorough body of documentation on this sort of thing. IMHO, the best resource would be the numerous open source bootloaders that are available.
upofadown 10y ago
There isn't a lot there to document. At this point it counts as a part of our civilization. It's even on Wikipedia: * https://en.wikipedia.org/wiki/Master_boot_record https://en.wikipedia.org/wiki/Master_boot_record * https://en.wikipedia.org/wiki/BIOS_interrupt_call https://en.wikipedia.org/wiki/BIOS_interrupt_call There isn't much call for FAT12 these days...