March 15, 2010

Send That File To Hell, Part I

Filed under: Main — admin @ 12:01 am


Deleting a file isn’t what you think it is.

I suppose it’s pretty common knowledge how to zap a file out of existence: You click to select the file’s icon, then press the Delete key in Windows or Command+Delete on a Mac. Or you can be all graphical and drag the icon to the Recycle Bin or Trash. Simple.

What happens next depends on the operating system.

In Windows, the file is compressed and stored in a Recycle Bin archive. Information about the file’s folder location is also kept, so that it can be restored to its original spot later.

On the Mac, the file is merely moved to the Trash folder.

So a deleted file isn’t really deleted; it’s moved to another location, out of sight. This operation came about because early operating systems really did take efforts at removing the file; the end result of a file delete operation was that you couldn’t get the file back, no matter how hard you hit the computer’s monitor.

Peter Norton made a fortune by crafting the first popular un-erase utility back in the early 1980s. Obviously people were hasty with deleting files and there was widespread need to get them back.

Eventually the operating system developers caught on, and today you have things like the Recycle Bin or Trash.

(Poor Peter lost his monopoly when DOS gained an UNDELETE command.)

For those time when you want to really delete a file, you can use special file-deleting commands. In Windows, it’s Shift-Delete, which zaps a file and doesn’t put it into the Recycle Bin for recovery.

The Mac doesn’t seem to have a permanent delete command specifically. You can, however, choose the option Secure Empty Trash from the Finder menu, which utterly zaps deleted files.

Now you can understand how deleting a file doesn’t really delete it. In fact, deleting a file in the old days didn’t really delete it, either. That secret was how Norton was able to work his magic in the un-erase program. I’ll describe more of the behind-the-scenes part of deleting a file in Wednesday’s blog post.

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