What bootsect. s does

1. Move yourself (512b) to 0x90000 and continue executing in a new place.

 

2. Copy the setup module of the four sectors starting from the second sector of the disk to 0x90200, that is, after bootsect

 

3. Save the maximum number of sectors per track to the variable sectors, and use init 0x13 to judge the file system. In Step 5

 

4. Load the system module at 0x10000,

 

5. Confirm the device Number of the root file system and save it to root_dev for use by the setup module.

 

6. Jump to the setup module and execute