Data Air

Discussion in 'Programmer's Corner' started by tahir51214, May 9, 2013.

  1. tahir51214

    Thread Starter New Member

    Nov 11, 2011
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    My question is lil funny but Let me ask it. Where does this data go, Which is deleted by us from our computers or phones? I know it is not matter but still ...........
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
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    When you delete data from a compter, it goes in the "Recycle Bin". You can go there and retrieve the data if needed. However, occasionally you empty the Recycle Bin. That data is simple erased from your disk. It just vanishes.
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    Depends. If it is data saved on a server, cloud, Facebook, Linkedin, Twitter, YouTube, forum, email, etc. when you delete your data the information is still backed up somewhere. It potentially never goes away.
     
  4. tahir51214

    Thread Starter New Member

    Nov 11, 2011
    29
    1
    I created a file in MS word. I uploaded it no where. Im deleting it now. Even from my hard drive permanently, Now where it went away?????????????
     
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  5. MrChips

    Moderator

    Oct 2, 2009
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    If it is a file on your hard drive, the information was written as patterns of 0's and 1's on the magnetic disk. When you delete the file, all you have done is to set a check mark to tell the operating system not to look for that file any longer.
    The information is still on the disk and may be recovered later.
     
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  6. vpoko

    Member

    Jan 5, 2012
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    That's actually a very interesting question. In order to clear a bit from memory - a bit that's represented by some voltage (with reference to ground), we have to sink that bit. The energy that was formerly stored there is radiated away. That's the reason processors get hot, and why reversible computing, where every change in a bit from a 1 to a 0 is paired with a corresponding change from a 0 to a 1 (and vice versa), is an active area of research.

    There are reversible logic gates that have been shown to be universal: namely the Fredkin gate and the Toffoli gate. Other than their importance for energy efficiency purposes (because they allow reversibility), they're critical in quantum circuits, which *must* be reversible because quantum systems are unitary.
     
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  7. vpoko

    Member

    Jan 5, 2012
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    The file is bits. If not right away, then later (when you try to write over the same area of the disk where the file was), those bits will be replaced by other bits - some bits will remain the same, and others will be flipped. It will no longer encode the information that made up your file, once the specific sequence of bits that made up your file no longer exists, then neither does your file. Unless files have a soul, of course.
     
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  8. MrChips

    Moderator

    Oct 2, 2009
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    What?

    Processors get hot because they consumer electrical power, P = I x V.
     
  9. vpoko

    Member

    Jan 5, 2012
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    Yeah, but why does a processor consume electrical power? The goal is information processing. When you store a bit in a processor register, you've created potential with regard to ground. Once that register is shorted to ground (and the bit is cleared), then the circuit is complete, power is "consumed", and the processor has done what we wanted it to do. Of course there is resistive loss as electrons (and holes) move through the semiconductor, by the whole reason for the processor being powered is to read and write bits.
     
  10. MrChips

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    I think you are getting a bit carried away here. You don't have to get involved with reading and writing bits. That is a completely different issue.

    The reason a digital circuit consumes power is because when a transistor switches state from on to off or off to on, it needs to move the charge from one place to another. Moving the charge is what takes energy.
     
  11. vpoko

    Member

    Jan 5, 2012
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    I don't think we really disagree here.

    But why do reversible computers offer the potential improvement in energy efficiency (and they do)? It's because every time you've sunk a bit, if you want a new 1, you have to source more current. If the same bits were "recycled", you'd still be using power, like you said, to power transistors, and from resistive losses, but you would use less power (and dissipate less heat) than with non-reversible computers.

    See: http://www.technologyreview.com/view/422511/the-fantastical-promise-of-reversible-computing/
     
  12. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Think of your hard drive as a huge whiteboard. When you create a file and save it to disk, it gets written on the whiteboard. If you delete the file, it gets crossed out, but you can still read it and hence get it back.
    If your whiteboard gets full (no more white space), the system will go back and start erasing and writing over the deleted files. At this point, you cannot get the information back (normally without expensive equipment) There may be other cases based on individual programming of operating systems, but ignore them for this example, please.
    So where does the data go? One could say into little dust bits of the erased ink, like the lost charges used to store the original data. But once erased, it's gone.
     
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  13. MrChips

    Moderator

    Oct 2, 2009
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    Here is another analogy. Have you ever played a game of GO, Othello or Checkers?

    Imagine a checker board where all the squares are covered with a checker piece. In this case, all the pieces are Othello pieces, i.e. white on one side and black on the other.

    Now arrange the pieces in any way you wish, with the white or black side showing.
    Let us imagine that on the first row you have created a pretty pattern of your choice. That represents your data on the computer file.

    Now you tell the operating system you no longer want that row and you are going to use a new pattern on row #2. You have "deleted" your data on row #1 but it is still there.

    It is not until when you or someone else alters the pattern on row #1 does the information becomes changed and hence the previous pattern is lost.

    The data on a computer disk or memory works in exactly the same way.
     
  14. WBahn

    Moderator

    Mar 31, 2012
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    Of course, not all systems behave this way. Instead of just setting a flag telling the file system that a file is no longer valid, systems intended for highly classified data use utilities that immediately randomize (many times, usually) data that is deleted. Then, on top of that, the drive that the data was once on became classified as soon as that data was first put on there. So the only way to get rid of the drive is to physically turn it into itty bitty chunks of this and that with a mongo shredder. I don't know if they still magnetically degauss the entire drive before sending it to the secure shredding facility or not.
     
  15. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I believe it was back in the 1960's or 70's that semiconductor manufactures first investigated this problem as it dealt with shift registers. As you may know, a simple shift register is a series of flip flops where data enters one flip flop and comes out further down the chain. In the middle the data is passed from flip flop to the next, but what about the last flip flop? Where does THAT data go?

    It was determined this data (and eventually all digital data) goes into a bit bucket. The bit bucket contains all data once no longer needed.

    That sucker must be getting HUGE these days.
     
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