Contrary to popular belief, the moment you delete a file, it does not magically disappear from the hard drive. In fact, for this particular question, we will only be considering the Windows Operating System. Windows, in particular, keeps track of all files present on the Hard Drive. This is done with the help of things known as “pointers.”
Each file or folder on the Hard Disk has a pointer that tells Windows where the particular file is located on the Hard Disk. When you delete a file, Windows removes the pointer and changes the file location status to available. From the file system point of view, in the Operating System, the file is no longer present on the Hard Drive, and the sector that contained the file is considered free space.
However, there is a catch! Until the Windows OS rewrites new data on the available sectors, the file still exists and is very much recoverable. There are file recovery programs that can scan the hard drive for these deleted files and restore them. Now, the question might arise as to why the computer does not simply go ahead and delete the files directly. Well, the answer to that is pretty simple.
Deleting a pointer is much faster than deleting all the data present in that particular sector. For example, if you’ve ever noticed, deleting a 10 GB file is almost instantaneous, as compared to writing a 10 GB file. Erasing a 10 GB file takes as much time as writing it down. The only time it is truly deleted or erased is when new data is written on top of a sector that does not have a pointer towards it (deleted file).
All of the info above relates to how memory is handled in terms of a hard drive, but Solid State Drives works differently. A memory sector in an SSD is known as a flash cell. When you use an SSD, the files are instantaneously erased, regardless of the operating system involved in it. In an SSD, data cannot be written on top of existing data present within a flash cell. To write down the data, the first thing that must be done is that the data in the flash cell must be erased. Thus, the next time you do delete a file, remember that it’s still lingering around in your hard drive somewhere, unless you have an SSD!