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DMcCunney is correct, though I'd caution that just because you didn't save it on the hard drive, doesn't mean that it wasn't on your hard drive (as a temporary file saved by the program working with the data or RAM that was swapped to disk). You might want to secure delete your temp folder and secure overwrite all empty space now and then. Also, SSDs change the game a lot because they logically remap the physical space to do wear balancing and overwriting a file in place to do a secure wipe doesn't guarantee that it's actually overwritten. For this reason many SSDs provide a secure wipe mechanism, but they usually (AFAIK) only wipe the entire drive, not just the free space. A periodic wipe of free space by creating a HUGE file that fills all empty space can help with that, **BUT** most hard drives (both SSD and mechanical) also reserve an area to use as the drive starts detecting errors, remapping bad sectors into the reserve space. Any data that was in the areas marked as bad is potentially still laying around. Again, the reason why drive manufacturers provide a secure wipe functionality for the drive because the internal details of that remapping and bad space are hidden from the operating system -- only the drive knows about it.
If you care that much about your data security you MUST use an encrypted filesystem from day one and destroy it when you're done with it.
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