Днешната сесия за въпроси и отговори ни идва с любезното съдействие на SuperUser - подразделение на Stack Exchange - обединяване на уеб сайтове с въпроси и отговори.
Снимката е предоставена от Светът на Герард (Flickr).
Въпроса
Четец на SuperUser Shea A. иска да знае какво се случва с изтритите файлове на компютър:
Correct me if I am wrong here, but when you delete something from your PC, all your computer does is write over some of the binary with 0’s replacing the 1’s (or something to that effect). So when you send something to the Recycle Bin, it writes over part of the file, then when you delete the file from the Recycle Bin, it writes more?
Как точно работи процесът за изтриване на целия файл и кошчето?
Отговорът
Сътрудниците на SuperUser Boann и Mary Biggs имат отговор за нас. На първо място, Боан:
Neither operation writes over the file. Moving a file to the Recycle Bin does just that, moves the file. Its contents are left completely intact.
Deleting a file from the Recycle Bin (or deleting it directly using Shift+Delete) removes the file name entry from the folder. The part of the disk previously occupied by the file is not modified or overwritten and still contains the file data, but that data is no longer linked to a file name. That spot on the disk is recorded as “free”, however, so future writes to the disk can reuse that space, and if you keep using the disk, the space will almost certainly be overwritten eventually.
In a case where you need to prevent recovery of deleted data, special tools exist to overwrite the data securely. That is not done by default because it is slow and increases wear on the disk.
Последвано от отговора на Mary Biggs:
A file is in two parts:
- A directory entry which records the file name and also contains a list of the blocks on disk which contain the data contents of the file. The operating system then “knows” that these blocks are in use.
- The actual blocks which contain the data contents of the file.
When a file is deleted:
- The list of blocks in the directory entry are marked as “free” and returned to the operating system. The directory entry is deleted, so the file “disappears” from the file system.
- The actual blocks are not touched, so the data contents of the file remain untouched until some other new file overwrites them. This is the reason that file recovery software can often rebuild deleted files (but only if it is used soon after deletion).
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