看看是什么问题,说的有理送100分!急

函数名: biosdisk
功 能: 软硬盘I/O
用 法: int biosdisk(int cmd, int drive, int head, int track, int sector
int nsects, void *buffer);
程序例:

#include <bios.h>
#include <stdio.h>

int main(void)
{
int result;
char buffer[512];

printf("Testing to see if drive a: is ready\n");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Ready\n")) :
(printf("Drive A: Not Ready\n"));

return 0;

}
这个程序在win2k server下运行是正确的但在dos下会出错
我把biosdisk(4,0,0,0,0,1,buffer);改为biosdisk(4,7,0,0,0,1,buffer); 也就是对H盘进行操作,却报错,H盘是非32M的flash card 请问哪里有错误?