第一个段为安装程序，负责将第二个段写入第一扇区，第三个段写入2-17扇区；



2、第二个段是主引导程序，存在于软盘第一扇区，由BIOS的19h中断读取到0:7c00开始的内存单元中，并执行0:7c00的第一行代码。这一段的任务是将软盘2-17扇区的数据读入内存，并执行。（这里读入到了2000：0开始的内存中）



3、第三个段是系统程序，存放所有引导所需的程序和子程序-The first segment of the installer, is responsible for writing the first sector of the second paragraph, the third paragraph is written 2-17 sectors　2, the second segment is the master boot program, there is a floppy disk first fan area by the BIOS interrupt 19h to 0:7 c00 start reading memory unit, and performs 0:7 c00 first line of code. The task of this section is to floppy 2-17 sector data is read into memory and executed. (Here read into the memory beginning 2000:0) 3, the third segment is the system program stored all the required programs and subroutines guide