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Comments on Program coding:
In the program coding given earlier, basically we are proceeding to perform the following tasks step by step:
- dinfo points to the diskinfo_t structure that contains the information of parameters required by the operation performed by the _bios_disk function.
- Since we want to read first sector of the disk therefore the location of the sector will be as follows:
Parameter |
What it means |
dinfo.drive = 0x00 |
It indicates the drive 0 that is floppy disk drive (a:) |
dinfo.head = 0 |
It points to head number 0 |
dinfo.track = 0 |
It points to track 0 |
dinfo.sector = 1 |
First sector of the floppy that is sector 1 |
dinfo.sector = 1 |
Number of sectors to consider for read operation = 1 |
dinfo.buffer = dbuf |
Data buffer for the operation |
- Open a file stream of user given file name and path to store the boot image information of exact 512 bytes. The file name and path is stored in the character array fname.
- Initialize the disk system using the interrupt 13H (function 00h) where regs.h.ah = 0x00 points to the function 00 H and regs.h.dl = 0x00 is used for a: floppy. And int86(0x13, ®s, ®s) invokes MS-DOS interrupt service INT 13 H.
- _bios_disk(_DISK_READ, &dinfo) reads the specified sector of the floppy disk.
- The status returned is stored in result that is used to display the message for successful operation or to display an error message on the screen if any error occurs.
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