Windows 9x
Windows 9x provides a vxd called vwin32.vxd using which msdos functions including absolute disk read/write can be performed. A handle to vwin32.vxd must be first created using the CreateFile function. After creating the handle DeviceIoControl function must be used with the correct control code to read or write from the disk drives. The control code depends on the type of the function you want to perform.
The control codes for vwin32.vxd are ...
Code |
Description |
VWIN32_DIOC_DOS_IOCTL (1) |
Interrupt 21h Function 4400h through 4411h |
VWIN32_DIOC_DOS_INT25 (2) |
Performs the Absolute Disk Read command (Interrupt 25h) |
VWIN32_DIOC_DOS_INT26 (3) |
Performs the Absolute Disk Write command (Interrupt 25h) |
VWIN32_DIOC_DOS_INT13 (4) |
Performs Interrupt 13h commands |
VWIN32_DIOC_DOS_DRIVEINFO (6) |
Interrupt 21h Function 730X commands |
The lpvInBuffer & lpvOutBuffer params of DeviceIoControl function must point to addresses of DIOC_REGISTERS structures . This structure contains the state of the processor registers before ioctl and after ioctl.
Windows NT/2K/XP
In Windows NT/2K/XP the CreateFile function can be used to open a disk drive or a partition on it. After getting a handle to the disk drive using CreateFile function the ReadFile function can be used to read sectors and the WriteFile function can be used to write to the drive.If you want to open a logical drive give the filename param of the CreateFile function as "\\\\.\\a:" or "\\\\.\\c:" ... etc. and if you want to open a physical drive for raw reading/writing give the filename param as "\\\\.\\PhysicalDrive0" or "\\\\.\\PhysicalDrive1" ... etc
Code to read disk sectors from win 9x/NT/2K/XP
Reads [numberofsectors] disk sectors from [drive {0=A, 1=B, 2=C, ...}] drive starting from [startinglogicalsector]
To read sectors from win 9x int 21h's 7305h extention is used (Extended Absolute Disk Read/Write). For more info about int 21h's 7305h extention refer Ralf Brown's interrupt list.
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