Re: DOS 3.3 Nibble Encoding

[vandry@CAM.ORG (Phillip Vandry)]

dempson@swell.actrix.gen.nz (David Empson) writes:

>ProDOS's boot sector reads the second sector belonging to block 0,
>then the pair of them attempt to read the file called PRODOS into
>memory and transfer control to it.

I've always been amazed that it is possible to read a file into memory
from a program less than 512 bytes long. There's a lot to do! You need to
read block 2 (which is a nontrivial task -- you can't just make a ReadBlock
call, you need to implement one!). You may need to read more directory
blocks. Then you need to handle the sapling storage type. You also have
to convert tracks/sectors to blocks!!

How can this possibily be done in 512 bytes? Is there some secret to it?

-Phil