What makes a boot disk boot?

[ca9mbu]

I love getting way ahead of myself! I've only just started learning assembly, but it got me thinking about producing an operating system! Because everything's at such a low level and .asm is insanely fast in comparison to higher level languages it seems the ideal language to use for a lot of the very low-level OS stuff. So my actual question is how do I make a floppy disk bootable (in that a machine with no OS installed can start from it)?

http://www.slip.net/~galileo/

[Darkwraith]

Because the previous link is down...

http://www.experts-exchange.com/Programming/Programming_Languages/Assembly/Q_20638017.html

[Peter Swinkels]

As far as I can tell any program less than 512 bytes running
independently from any operating system can simply
be written to sector number 0 of a disk which will be loaded and executed when booting from the disk.

One of the easiest ways to experiment with this I can think of
is to use Debug.exe to create a small assembly program and
to then write it to a disk.

The BIOS will load 512 bytes from the first sector on any disk it attempts to boot from and execute it as a computer program.