In our daily life, we occasionally have such experiences:combine pdfs for free windows a data file that was downloaded with great difficulty is accidentally deleted by mistake, or the computer is straining on the keyboard and the screen suddenly goes black.
In this case, don't worry because the real data is still in the computer.
If you want to get back the mistakenly deleted files,convert scanned pdf to word online free large files you must first understand where the computer files go after we click delete.
How do computer files do data saving?
Before that, we need to understand some concepts.
All computer files, including the operating system, are stored on the hard disk. Generally speaking, no matter what kind of mechanical hard disk, it consists of disks, heads, disk spindles, control motors,pdf editor online head controllers, data converters, interfaces, caches, and so on.
Disks are formatted into many concentric circles called tracks.
The same track on all disks forms a platen, often called a cylinder, and the heads on each platen are numbered from top to bottom starting at "0".
The operations management system stores information on the hard disk in the form of sectors, each of which consists of 512 bytes of data and some other related information. A sector has two main important parts, the identifier of the location where the spatial data is stored and the data segment where the technical data is stored.
Considering the above concepts, we briefly describe the process of reading and writing files.
First of all, when the operating system stores a file on a disk, it does so in a columned, head and sector fashion, i.e., all sectors under the first head of the first track are stored first, and then the next head of the same columned surface is stored. And so on, when a platen is full, it advances to the next platen until all the file contents are written to the disk.
What is the process of deleting a file?
Now that you know the general principles of file reading and writing, let's talk about today's topic - file deletion.
The physical formalism of file storage is to save some binary information data on disk, if necessary we want to delete a file, just like a we write homework with an eraser or correction fluid to erase the existing text is also the same.
However, as you know, reading and writing computer files is above all high-speed and frequent. Copying a movie usually takes at least ten seconds. On the other hand, if you want to delete a movie from your hard disk, if we follow the principle of modifying the operation with correction fluid, we have to overwrite it with new data. If that's the case, wouldn't it take a few seconds to delete a movie? This is not reasonable for the computer itself or for the computer user.
So the computer's operating system (such as the commonly used windows 10) generally only deletes references to files, logically freeing up the physical space on the disk that the file once occupied. If there is a new data store later, a direct overwrite on this basis is sufficient. So let's be clear here, if your files are accidentally deleted or corrupted, stop any write operations immediately.
On the hard disk, there is a FAT file allocation table, which records the specific location of each file stored on the disk, we can understand it as a new Chinese dictionary directory, indicating the corresponding page number of each text, the fat works in roughly the same way.
When we delete a file, the operating system only modifies the first two codes of the file name of this file, and at the same time, the file name in the table corresponding to it is marked for deletion.
For this, we can understand that the file area on the hard disk is marked as "demolished" and its coordinates are erased from the map, but it is still there.
When we need new space for storage, any area that has been marked "demolished" can be used to store new data, i.e. be overwritten by the new data.
So naturally, as long as no new data has been written to the sectors where the original file information was stored, all the original file content is still there.
So, it is clear: the deleted files in your computer still exist on your hard disk until they are overwritten by new data.
Can deleted files be recovered?
Here we have almost understood the general situation of file deletion, can we reverse the principle of file recovery?
In fact, it is very simple, the idea of file recovery is to find and analyze the file header on the disk, find out which files have been marked for deletion and try to rewrite their rewritten two code, and then data recovery.
Currently on the market file recovery software principle is basically the same, the difference is the scanning file header and the ability to recover fragmented file data is different.
If you want to really delete a file, what should you do? You can use professional tools and software to write all the zeros in the binary in the deleted file area, or you can manually overwrite the hard disk operation with other junk files.