no, it isn't. you have to write "zero" to make sure all data is actually GONE. otherwise its there. imagine it like this. the table is the keystone. it tell where EVERYTHING is, how to access it, so on and so on. when you format you are esentially telling it that this information is available for use. you remove the keystone, or the directory. ALL the information is there and can STILL be accessed with the proper tools and deep enough pocket book. there is no refernce now on HOW to get the data. BETTER YET! It's like you got amnesia and can't remember how to get home. Does that mean home doesn't exist? No, its there. You just dont know where. No if home was destroyed, then that would be writing a zero... or making it into nothing.
Say I tell you to goto Greshem, Oregon. No map, no street signs, no nothing. Or anywhere for that matter. How will you find it? Good luck. The table would be like me giving you a map. Here is where it is and here is how to get there, here is what to get, and here is where to go next if not home. You can format over and over, all it will do is maybe bring your MTF closer (HD failure). Now, writing zeroes would be like me nuking the whole place. No map. Hell, Greshem just DOESN"T exist anymore. Weird analogy, but if the above didn't get you (and I think his was much better
), then try looking online for hard drive mechanics or engineering. It'll give more indepth on the physical workings.