INT 19H: Bootstrap Loader

 This vector is taken after the POST in order to attempt to load and
 execute any bootstrap code on diskette or hard disk.

 The data in sector 1 of track 0 of head 0 of the first responding disk
 (diskette or hard disk) is loaded at absolute address 0000:7c00 and
 control is given to that address.  On the oldest IBM-logoed systems,
 control goes to INT 18H (to start ROM BASIC) if all disks fail.

 On a hard disk, the bootstrap code determines which partition is active,
 and then loads and executes the boot sector for that partition.

 See Disk Partition Table for more info on the hard disk boot sequence.
 See Boot Sector Layout for info on the format of the DOS boot sector.

    Note: You can use this service to reboot DOS after changing some values
          in the Equipment List or other variables in the BIOS Data Area
          (be sure 0040:0072 is set to 1234H).

          After a reboot, DOS will notice any changes you made.

See Also: ROM-BIOS Functions
          BIOS Data Area