Computers take Shortcuts
To a computer, any file is nothing more than a long series of ones and zeros. A single file, even a small one, contains a large number of ones and zeros. So many, that it would take a very long time to actually get rid everything. Instead, it takes a shortcut… it doesn’t actually erase the file, it just erases the very beginning of the file. Doing this makes that space on your disk look as though it is available for a new file to live once one is created.
Because of this shortcut whenever you delete a file, it isn’t truly gone at first. It will only be gone for good when 1) you create a new file and 2) the computer decides that the deleted file is a good place to write it down. Still, even when this happens, the file can still exist partially if, for example, the new file is smaller than the older file.
How Data Recovery Works
Data recovery scans your disk for data that has lost its “beginning” point. Then it tries to figure out what kind of file it used to be. Once it knows that, it adds back the parts that were removed and the file lives again!
When Data Can No Longer Be Recovered
The age of a deleted file has nothing to do if it is recoverable. The real reason files become unrecoverable comes down to how many new files the computer is making. If you download large files, if you make new files often, the computer is going to need somewhere to write the file’s data – and sooner or later it’ll pick the space an old deleted file used to be. When that happens, the file loses the ability to be fully recovered. Is it too late to recover a file? Maybe not! It depends on how much new data is created on your computer – so if you do not add new things to your computer it might be very easy to recover a deleted file.
Recovering from Re-Formated Disks
Reformatting a disk doesn’t usually erase its contents. To erase a disk, your hard drive has to write millions, billions, or even trillions of zeros, and this process can take hours or even days. Instead, reformatted disks do a “quick format” and erase its record of files, not the files themselves. Data recovery software can still work, however the life of a deleted file is shorter because the computer is not very pick about where to make its new files.