What happens to files when we delete them?

Question

When we delete files on a computer where does all the information go. I was wondering how something that exists can completely disappear as if it never existed.

We learned in Chemistry that matter or energy cannot be destroyed or created. Although this is physics, shouldn't this also apply to computers?

Answer 1

well if you draw a line with your pencil....cant you erase it!?!  

Answer 2

The data never exists as such. It is made up of simple on and off signals or when stored is a series of 1s and 0s stored as a magnetic pattern on the disk. They machine keeps a list of all files and knows from this where they are. When you delete them the list marks their original space as unoccupied. Your next save (can be a file you save or a temporary system file) simply modifies all the disk area to its' own pattern. The physical storage area is still there, it has just changed.

Answer 3

When you delete a file from your PC it is not actually deleted. The PC just 'marks' the section of harddrive as available so that something else can be saved there. The data is still there until it is overwritten by something else.

The data only exists in a physical sense in the form of tiny magnetic fields, which don't disappear, they are just reshuffled when that section of harddrive is overwritten.

Answer 4

The go to file heaven where they play happily......

But seriously, what actually happens is the pointer to the file, in the FAT (file allocation table) is removed, but the file contents itself remain on the disk until they are overwritten (the area the former file occupies is marked as available for use).  There are secure programs which will also "remove" the file from your hard drive, but all these do is overwrite the area occupied by the former file when the FAT pointer is removed.

Regarding the second part of your question, the file never "really" exists.  It is an illusion created by a series of binary states (0s or 1s) on the individual elements of the hard drive.  These are like switches, they are either on or off, and are read and interpreted by your computer and displayed as the file contents.  When the file is removed by the secure means, the switches are all set to off (or random settings), so the hard drive hardware isn't physically changed with regard to the energy it contains, only the manifestation/configuration of that energy (0 or 1).

Answer 5

Deleted files are not completely removed from your hard-drive. When delete is requested, the pc writes 0 to the file address, this prevents it from being opened via normal operating methods.

The only way to completely delete files is to "zero write" the hard-drive ie format the hard-drive in such a way that the entire disc information is rewritten with zeros.

This is how it is posible for the police (and crooks) to read files from your PC even though you think that they have been deleted.

Answer 6

Your file is a sequence of 0 and 1 in the hard disk memory.Every memory location can have either 0 or 1 and the file occupied a number of those memory location in the hard disk. When you delete it, it actually copies to the bin folder and can be retrieved later. If you delete the file in the bin folder by clicking the empty bin command, the program is really erased to the user's sense.

However, erasing a file only means that some flags of the memory location is up that indicate the space can be used by other programs or files. It doesn't erase all the file information unless another program writes data into the position of the original file. In the latter case, the original file is completely destroyed and cannot be retrieved.

Erasing the file do not have anything to do with energy conservation. It merely changed the ordered sequence 0 and 1 to an unordered one.