ndk

Right, but my understanding was that the two-step process is necessary even if there's only one OS, that's why I haven't mentioned it. Right, the bootstrap loader has to load the OS from disk into memory. But isn't the bootstrap loader on disk as well? From what I understand, the BIOS has a tiny program that loads the bootstrap loader into memory and transfers control to it. Then the bootstrap loader loads the OS. My question was why can't the BIOS program load the OS directly. From reading some more, one reason might be that the BIOS program needs to be very small (to conserve ROM space?) - too small to contain all the instructions needed to load the OS, but big enough to load the bootstrap loader (which is much smaller than the OS - typically one disk sector). Is this correct? Are there other reasons? Thanks for the replies so far.

I thought bootstrapping means loading the OS?

From what I understand, when a computer powers up, the instruction register (IR) is loaded with a predefined location, which contains the bootstrap loader. Its job is to load the OS kernel and transfer control to it. 1) Why is this a two-step process? Why isn't it possible to load the address of the OS into the IR directly? 2) In various articles I found, it is mentioned that the bootstrap loader fits in a single disk block. Why is this significant? Thanks in advance.