absread( ) problem

Posted on 2002-05-17
Last Modified: 2010-08-05
i am not able to access the hard disk sectors with the absread() function  of borland turboc C++.
errno states that the function number is not correct.i also tried to use int25h which absread uses but all in vain.please help.thanks
Question by:vinayak_j
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Expert Comment

ID: 7016866
What is the operating system that you are using?  In protected-mode, multithreaded O/Ses like Windows, low-level disk access is disallowed in order to prevent disk corruption.

Sometimes you can lock a disk before attempting low-level access.

-- Dan

Author Comment

ID: 7017780
thanks DanRollins.I am using win98SE can you throw more light on locking disks the way i should access them.
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Accepted Solution

DanRollins earned 50 total points
ID: 7018316
You can look into the DeviceIoControl Win32 API.  It provides access to low-level information about a hard disk.  To access this function, you need to use the CreateFile() API as decribed here (section about physical drives):

And the FSCTL_LOCK_VOLUME Ioctl code that is described here:

The most common use for sector-level disk writing is to cause damage to people's hard disk as part of a virus or trojan horse type program.  So don't expect me to hold your hand.  If you have a real and legitimate interest in low-level disk I/O these links will get you started.

-- Dan
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Expert Comment

ID: 7019668
Your win98SE might have formatted the hard-disk in FAT32 file format.

absread are so old that they don't know anything beyond FAT16. This might be the reason.
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