If I Delete Something, Is It Gone Forever?

Most of us have heard that when you delete something from your computer it's "not really gone." Which inevitably leads to the question of "How do I make it really gone?" In order to really understand why deleting something doesn't obliterate it, you first need a quick primer on hard drives. If you haven't already read the article on How Do Computers Remember Things, click here to go over it- we'll be building on topics covered in there.

When a hard drive remembers something (aka "saves" it) it doesn't usually write it down in one spot on it's discs. It usually spreads it out and puts different parts in different spots, and creates a sort of mini table of contents so it can quickly find all the spots. It does this so if there's a small problem with one of the discs, it might affect a small part of a file and therefor keep it still usable, whereas if all the parts were together, the entire file would be broken.

When you delete something, it doesn't actually delete the different parts scattered about your drive. Instead, it deletes that table of contents file and thereby forgets it. Eventually the hard drive will put other files in that same space (remember, hard drives are magnetic so it can easily be rewritten), but until then, that part of the file is there as good as new. As time goes on, it becomes harder and harder to read part of a file that's been rewritten, much like if you wrote something on paper with a pencil, erased it, wrote something else over that spot, erased that, and so on. Each time it gets harder to read what was originally there.

There are ways to make things more permanently gone. For example, the Mac has an option called "Secure Empty Trash" that will first delete the parts of the file by re-writing over them seven times with random 1's and 0's (click here if you don't know why 1's and 0's) and then delete the table of contents file. There are similar things on Windows and other types of computers. If you use a method like this, it's highly unlikely that the file would ever be able to be found. (I never say never on these kinds of things!)

Practical Tip of the Day:
While it might be tempting to use one of those permanently delete options like Secure Empty Trash, you don't want to use it frivolously. Just like the paper beign written on and erased in the analogy, extra wear is put on the hard drive when you use these methods, and therefor slightly shortened the lifespan of your drive. My general rule of thumb for when to use this method is this: If this were a physical document, would you put it in the trash or shred it? If shred it, then use that method, otherwise, don't worry.