§7.3继承与构造函数、析构函数 单继承举例 磁盘 DISK name Sides tracks sectors byte per sector FLOPPY DISK HARD DISK write protect controller type§7.3 继承与构造函数、析构函数 单继承举例  磁盘 DISK name sides tracks sectors byte per sector FLOPPY DISK write protect HARD DISK controller type