Comments on coding:
The structure geometry is used by getdrivegeometry function using INT 13H Extension, Function Number 0x48 to get the various parameters of the disk.
The structure diskaddrpacket is for Disk Address packet format, to be used by the writeabsolutesectors Function.
The Function getdrivegeometry (int drive) is to get Drive Parameters of the disk specified physical drive number drive. buffer [61440] is the data buffer of 61440 bytes, Equivalent to 120 Sectors.
(char) peekb(0x0040, 0x0075) is used to find the number of hard disks connected to the computer, stored at memory location represented by segment 0040H:offset 0075H. If total number of hard disks attached is less then two Display Error Message and Exit.
writeabsolutesectors ( 0x81, loop, 120, buffer ) function is used to write the data of data buffer on 120 sectors at a time starting from the absolute sector number specified by loop.
I chose ‘\0’ (NULL character, ASCII code 0) to write on the sectors to overwrite the data. However you can use random characters to overwrite the data.
For detailed description on Functions writeabsolutesectors and getdrivegeometry refer the chapters given earlier in this book.
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