做过mp3的朋友指教程序中这句话怎么理解？

mcuhost

The first sector of cluster 2 (the data region of the disk) is computed using the BPB fields for the

volume as follows. First, we determine the count of sectors occupied by the root directory:

RootDirSectors = ((BPB_RootEntCnt * 32) + (BPB_BytsPerSec – 1)) / BPB_BytsPerSec;



以下是BPB_RootEntCnt的说明：



BPB_RootEntCnt  For FAT12 and FAT16 volumes, this field contains the count of 32-

byte directory entries in the root directory. For FAT32 volumes,

this field must be set to 0. For FAT12 and FAT16 volumes, this

value should always specify a count that when multiplied by 32

results in an even multiple of BPB_BytsPerSec. For maximum

compatibility, FAT16 volumes should use the value 512.





大家看看RootDirSectors = ((BPB_RootEntCnt * 32) + (BPB_BytsPerSec – 1)) / BPB_BytsPerSec;是怎么得出来的？望指教！谢谢！！


-----此内容被mcuhost于2007-06-07,10:18:48编辑过

blackcafe

RootDirSectors = ((BPB_RootEntCnt * 32) + (BPB_BytsPerSec – 1)) / BPB_BytsPerSec

BPB_RootEntCnt:根目录入口项数，每项32字节

BPB_BytsPerSec:每扇区(sector)字节数

所以根目录占用扇区数(RootDirSectors)=

RootDirSectors = ((BPB_RootEntCnt * 32) + (BPB_BytsPerSec – 1)) / BPB_BytsPerSec



+ (BPB_BytsPerSec – 1)是为了扇区数向上取整，即不足一扇区时也要分配1个扇区

mcuhost

多谢指教！！