Monday, September 6, 2010

Where do things go on your computer when you delete them?

Where do things go on your computer when you delete them?

When you delete a file on your computer it will likely end up in the recycle bin. So in that case, a bunch of associated bits making up the file have been moved from an application folder to the recycle bin. They are still located somewhere on your computer's hard drive in a recoverable format at this point. I am not going into any details other than to say that computer files (applications) consist of lots of 'bits' linked in special sequences to make up a file. But then I ask myself, what is a 'bit' of information? Now I am going to answer this question by saying that a 'bit' or binary digit is simply a 'single state of being', that is, it represents a 1 or 0 state. If so, how? In a bubble memory chip the state depends on magnetic orientation. In a read only memory chip (ROM) the state might be either an electrical path in the ROM that exists or it doesn't. I sure don't want to get into different types of ROM's, PROMS, RAMS, SRAMS, DRAMS and all sorts of their mutations. Just remember that one 'bit' of information can be stored in any fashion that enables you to determine its state when you want to check it. An empty glass could be a 0 state and a full glass could be a 1 state. Somehow I don't think that would be a very useful way to store information in a desktop computer. The whirling thing we call a 'hard drive' stores most of the information we use on a computer. We come back to the 'state of being' that I talked about earlier. That is, the something that represents a 1 or 0 (it is or it isn't) state. It is really easy to get off track talking about this subject of "Where do things go when you delete them." In a most simplistic manner of speaking, the 'hard drive' stores 'bits' on a spinning magnetic platter. The record head directionally magnetizes the ferromagnetic material on the spinning platter to represent a 'bit' (1 or 0) state. The read head reads the state back by detecting the magnetization at a particular location on the platter. Before going to a new paragraph I hate to do this but I must introduce the term 'Byte' which is just an ordered collection of 'bits'. Let me point out that each 'bit' within a 'byte' still has a binary value of 1 or 0. Think about it. In order to encode a single text character (A, B, C,?,/ and so forth) it takes an ordered collection of 'bits' to do so. So lets call that a 'byte' of information. Please don't ask how many 'bits' there are in a 'byte'. The modern de facto standard is 8 but most current digital processors use larger values and I don't want to talk about that here. Wow, I am glad we got through this part.

Well this is all and good but I go back to my original question of where do things go when you delete them on your computer? Its easier for me to visualize not having something if I know where it went after having been disposed of. For instance if throw a rotten potato in the garbage I have physically moved it from one place to another. When the garbage man picks up the trash it is again moved and I really don't care where it ends up at this point. I just know its not around stinking up the house and that was likely the reason for me putting it in the garbage in the first place. OK, I got off track. Lets say I no longer need a file or program on my computer and I move it to the recycle bin. So far I have only moved the file or program from one place to another and can restore the file from the recycle bin. Now I decide to empty the recycle bin to free up more space on my hard drive. So now, where did that file or program go? Is there some little pipe connected to the computer where the 'bits and bytes' fly out of my computer to places unknown? I have checked and haven't located a pipe. I will try to retrace my actions from when I first loaded the program on my computer. The program may have been downloaded from the Internet or it might have received on a CD or DVD. In the case of a CD or DVD I would have loaded or installed the program via my CD/DVD drive. So maybe what I did was copied the bits and bytes from the CD/DVD somehow to my hard drive. Now I see. Somehow little magnetic directional markers must have been created on my hard drive platter to represent the program material coming from the CD/DVD. So now I am understanding this better. The hard drive platter is made of magnetic material and the write head simply arranged the magnetic platter material to represent the data stream of 'bits' & 'bytes' being sent to it from the source CD/DVD. Wow, now that I kind of understand this I can see that to delete something is not actually throwing something out of my computer but rearranging it on the hard drive platter so it no longer represents the original data stream. So if I generalize, which is usually not a good idea, maybe I could say that things don't really go anywhere, like physically move, when I delete something from my computer. I might further say that the pattern and sequence of 'bits' & 'bytes' that originally represented a file or program has simply been randomized and the sophisticated pointers in the computer that did tell the computer where to look for a file no longer point to where the 'bits' & 'bytes' were once located.

Since I used the term 'pointer' I just want to say that the computer/drive maintains a road map of sorts that always knows where things are located on the hard drive (until a crash.) And if I kept on writing I might say that most of the time the 'bits' & 'bytes' are not randomized as in full security erasing but the pointer is simply reset. In a physical sense, sort of like loosing track of where you put your glasses from the night before.