使用 int 13h 读取的扇区数量多于磁道上的扇区数量

顺序是什么int 13h with ah=02h会读19部门起始于(C, H, S) = (0, 0, 1)提供了 2 个磁头、每磁道 18 个扇区、每面 80 个磁道的（软盘）磁盘几何结构。

或者，更一般地说，当它到达磁道 0 的末尾、磁头 0 时会发生什么？它转到磁道 1 还是磁头 1？在这种情况下它还能正常工作吗？

编辑：等等..这实际上就像小时、分钟、秒吗？如果我们到达轨道末端（S大于18），那么H会增加吗？

Modern BIOSes support the concept of multitrack¹ reads and writes. If you read or write past the end of a track it will continue on with the following track. To be most compatible with the widest array of BIOSes (old and new) you may wish to consider not reading or writing across a track boundary.

对于每磁道 18 个扇区/2 个磁头/80 个柱面的驱动器几何结构（3.5 英寸 1.44MB 软盘），CHS(0,0,18) 之后的扇区是 CHS(0,1,1)。在到达 CHS 处的扇区后(0,1,18) 下一个是 CHS(1,0,1)。在某种程度上，这类似于 HH:MM:SS。

根据您的驱动器几何形状，总共有 2880(80*2*18) 个扇区。如果将扇区编号为 0 到 2879（含），则它们称为逻辑块地址 (LBA)。

INT 13小时/ah=2 http://www.ctyme.com/intr/rb-0607.htm takes CHS价值观。您可以转换LBA to CHS具有以下公式（或等效公式）的值：

C = (LBA ÷ SPT) ÷ HPC
H = (LBA ÷ SPT) mod HPC
S = (LBA mod SPT) + 1

HPC = Heads per cylinder (aka Number of Heads)
SPT = Sectors per Track, 
LBA = logical block address

"mod" is the modulo operator (to get the remainder of a division)

我已经写了更多关于LBA to CHS在这个其他的计算堆栈溢出答案 https://stackoverflow.com/a/45495410/3857942在该部分LBA 到 CHS 的翻译。如果您使用这些计算创建了一个表，则编号将如下所示：

LBA =    0:   CHS = ( 0,  0,  1)
LBA =    1:   CHS = ( 0,  0,  2)
LBA =    2:   CHS = ( 0,  0,  3)
LBA =    3:   CHS = ( 0,  0,  4)
LBA =    4:   CHS = ( 0,  0,  5)
LBA =    5:   CHS = ( 0,  0,  6)
LBA =    6:   CHS = ( 0,  0,  7)
LBA =    7:   CHS = ( 0,  0,  8)
LBA =    8:   CHS = ( 0,  0,  9)
LBA =    9:   CHS = ( 0,  0, 10)
LBA =   10:   CHS = ( 0,  0, 11)
LBA =   11:   CHS = ( 0,  0, 12)
LBA =   12:   CHS = ( 0,  0, 13)
LBA =   13:   CHS = ( 0,  0, 14)
LBA =   14:   CHS = ( 0,  0, 15)
LBA =   15:   CHS = ( 0,  0, 16)
LBA =   16:   CHS = ( 0,  0, 17)
LBA =   17:   CHS = ( 0,  0, 18)
LBA =   18:   CHS = ( 0,  1,  1)
LBA =   19:   CHS = ( 0,  1,  2)
LBA =   20:   CHS = ( 0,  1,  3)
LBA =   21:   CHS = ( 0,  1,  4)
LBA =   22:   CHS = ( 0,  1,  5)
LBA =   23:   CHS = ( 0,  1,  6)
LBA =   24:   CHS = ( 0,  1,  7)
LBA =   25:   CHS = ( 0,  1,  8)
LBA =   26:   CHS = ( 0,  1,  9)
LBA =   27:   CHS = ( 0,  1, 10)
LBA =   28:   CHS = ( 0,  1, 11)
LBA =   29:   CHS = ( 0,  1, 12)
LBA =   30:   CHS = ( 0,  1, 13)
LBA =   31:   CHS = ( 0,  1, 14)
LBA =   32:   CHS = ( 0,  1, 15)
LBA =   33:   CHS = ( 0,  1, 16)
LBA =   34:   CHS = ( 0,  1, 17)
LBA =   35:   CHS = ( 0,  1, 18)
LBA =   36:   CHS = ( 1,  0,  1)
LBA =   37:   CHS = ( 1,  0,  2)
LBA =   38:   CHS = ( 1,  0,  3)
LBA =   39:   CHS = ( 1,  0,  4)
LBA =   40:   CHS = ( 1,  0,  5)
LBA =   41:   CHS = ( 1,  0,  6)

... [snip] ...

LBA = 2859:   CHS = (79,  0, 16)
LBA = 2860:   CHS = (79,  0, 17)
LBA = 2861:   CHS = (79,  0, 18)
LBA = 2862:   CHS = (79,  1,  1)
LBA = 2863:   CHS = (79,  1,  2)
LBA = 2864:   CHS = (79,  1,  3)
LBA = 2865:   CHS = (79,  1,  4)
LBA = 2866:   CHS = (79,  1,  5)
LBA = 2867:   CHS = (79,  1,  6)
LBA = 2868:   CHS = (79,  1,  7)
LBA = 2869:   CHS = (79,  1,  8)
LBA = 2870:   CHS = (79,  1,  9)
LBA = 2871:   CHS = (79,  1, 10)
LBA = 2872:   CHS = (79,  1, 11)
LBA = 2873:   CHS = (79,  1, 12)
LBA = 2874:   CHS = (79,  1, 13)
LBA = 2875:   CHS = (79,  1, 14)
LBA = 2876:   CHS = (79,  1, 15)
LBA = 2877:   CHS = (79,  1, 16)
LBA = 2878:   CHS = (79,  1, 17)
LBA = 2879:   CHS = (79,  1, 18)

脚注：

¹Multitrack support doesn't mean a disk access can cross cylinders. A multitrack disk access must start and end on the same cylinder.