If a file is deleted, say into the recycle bin and then the bin is emptied, what happens to the file? If it is restorable (somehow) from the hard drive, then it must be still there and therefore taking up space on the drive.
Our teachers say it is not there but is recoverable. I say that if it is recoverable, then it must be there. It can't be there and not there at the same time. Is this file taking up space or not? How do I permanently get rid of files I KNOW I won't want to recover?
When a file is deleted, it is moved to the recycle bin. The file is still there and it is still taking up space (it just in a different folder).
When the file is deleted from the Recycle Bin (folder), a couple things happen. First, the file name is removed from the file system. Next the first character of the file is changed. And finally, the allocated space for the file is marked as free.
So at this point, the file is still on the physical disk (only the first character has been changed). A recovery program would scan for that special first character, change it to something that can be read by the file system, and rebuild the file information (allocated space, end of file, etc.) and update the file system.
If a file is overwritten, this becomes harder since you have to read the magnetic remnants of the file. Special processes can do this and there are companies that focus in this area of data recovery. In fact, only after being overwritten over 31 times with specific bit patterns is the data deemed unrecoverable (according to US MilSpec).
Hope this helps.
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This was first published in September 2001