[Freedos-kernel] about boot sector

[cstarter]

%define bsOemName       bp+0x03      ; OEM label %define bsBytesPerSec   bp+0x0b      ; bytes/sector %define bsSecPerClust   bp+0x0d      ; sectors/allocation unit %define bsResSectors    bp+0x0e      ; # reserved sectors %define bsFATs          bp+0x10      ; # of fats %define bsRootDirEnts   bp+0x11      ; # of root dir entries %define bsSectors       bp+0x13      ; # sectors total in image %define bsMedia         bp+0x15      ; media descrip: fd=2side9sec, etc... %define sectPerFat      bp+0x16      ; # sectors in a fat %define sectPerTrack    bp+0x18      ; # sectors/track %define nHeads          bp+0x1a      ; # heads %define nHidden         bp+0x1c      ; # hidden sectors %define nSectorHuge     bp+0x20      ; # sectors if > 65536 %define xsectPerFat     bp+0x24      ; Sectors/Fat %define xrootClst       bp+0x2c      ; Starting cluster of root directory %define drive           bp+0x40      ; Drive number I read the boot code many times , the "bp+xxx" puzzled me . not value specified , how to calculate . I wonder the bsSectors's(nFATs ,...) value , and how to  calculate . Thanks .