Trash (computing)
In computing, the trash is a graphical user interface desktop metaphor for temporary storage for files set aside by the user for deletion, but not yet permanently erased. The concept and name is part of Macintosh operating systems, a similar implementation is called the Recycle Bin in Microsoft Windows, other operating systems use other names.

In the Finder or file manager, the Trash or Recycle Bin can be viewed by the user as a special Folder (file directory), allowing the user to browse the files and retain those still wanted before deleting the others permanently (either one by one, or via an 'empty trash' command). It may still be possible using third party software to undelete those that were deleted by mistake. In macOS, the Trash folder links to hidden folders on each mounted drive where the files are actually stored.

Within a trash folder, a record may be kept of each file and/or directory's original location, depending on the implementation. On certain operating systems, files must be moved out of the trash before they can be accessed again.

Whether or not files deleted by a program go to the recycle bin depends on its level of integration with a particular desktop environment and its function. Low-level utilities usually bypass this layer entirely and delete files immediately. A program that includes file manager functionality may or may not send files to the recycle bin, or it may allow the user to choose between these options.

History  
Bill Atkinson began developing the Apple Lisa user interface in late 1978. In March 1982 he reached the stage of changing to an icon-based file manager, and produced a mock-up with a trash can icon (including buzzing flies) for deleting files. The release version of Lisa was launched in 1983 with a "Wastebasket", its icon "an alley-style garbage can [with] vertical lines to indicate a ribbed surface .... an open lid and a handle on the front of the can." Apple advertised "If you can find the trash can, you can run a computer."

Following this, the Magic Desk I ROM cartridge for Commodore 64 presented a primitive representation of office furniture, with a wastebasket or trash bin under the desk. This lacked functionality and was not taken further.

In 1983 Susan Kare designed the core visual design language of Classic Mac OS System 1, launched in January 1984. This incorporated some elements of the Lisa interface, including a refined version of the icon, now labelled Trash, with "a closed lid with a handle on top." An ad supplement in Newsweek introduced the Mac interface, with its "pictures of objects you'll have no trouble recognizing ... Even a trash can." A subsequent update to Lisa renamed its Wastebasket icon "Trash".  In "International English" localizations of Classic Mac OS, Trash was named "Wastebasket".

In early versions of the Macintosh Finder, Trash contents were in volatile memory, and were lost when the computer restarted. From 1987, if anything was in Trash its icon bulged as a reminder to check the contents before shutting down. Following the 1991 introduction of System 7, the Trash folder retains its contents until the user chooses to empty the trash.

The outcome of the lawsuit Apple Computer, Inc. v. Microsoft Corp. (filed in 1988, decision affirmed on appeal in 1994) was that graphical user interfaces similar to Apple's did not infringe rights, but some features including Apple's Trash icon were original and protected by copyright. Non-Apple software could use other metaphors for file deletion, such as Recycle Bin, Smart Eraser, or Shredder.

In 1993 or 1994, Microsoft implemented its first temporary deletion system in MS-DOS 6, under the name Delete Sentry: When a file was deleted, it was moved to a hidden SENTRY folder at the root of the drive.

Microsoft introduced its current trash system in 1995, the Recycle Bin, with Windows 95, as an area to store and review files and folders prior to deletion. Unlike the mac, at default settings Recycle Bin auto-deletion permanently deletes files to free up disk space when it gets low, or deletes files in the Bin over 30 days. In this version, the original location record of the file is stored, but the folder itself didn't allow subdirectories. When a folder is deleted, its containing files are moved into the bin and mixed with other deleted files. The directory structure can only be restored if the batch of files is "undeleted". The current (revised) Recycle Bin allows for subdirectory trees to exist within folders that have been moved there. The icon shows a bin with a recycling symbol on its front.

With the new interface of Mac OS X introduced in 2001, the Trash icon moved from the desktop to a permanent place at the end of the Dock. The International English "Wastebasket" had been dropped at the end of 2009, making the name "Trash" standard. In keeping with the system appearance, the Trash was a shiny wire basket, until with OS X Yosemite in 2014 it became a translucent white container. With macOS Mojave, the Trash was renamed "Bin" in the Australian English localisation, and with macOS Catalina, "Bin" also appeared in the UK localisation.

Implementations 

Recycle bin functionality is usually integrated into a desktop environment and its file manager. Examples include:

 Classic Mac OS and macOS, with Finder, as "Trash" (localised as "Wastebasket", later "Bin")
 MS-DOS 6.x, with Microsoft Undelete, as "Delete Sentry"
 Microsoft Windows, with Windows Explorer (later called File Explorer starting with Windows 8), as "Recycle Bin"
 GNOME and MATE (Linux), with Nautilus and Caja, respectively
 KDE (Linux), with Konqueror and Dolphin
 Xfce (Linux), with Thunar
 Amiga, with Workbench. The Professional File System added trashcan-esque behavior at the filesystem level.
Some implementations may contain "shredding" functionality to counter data remanence.

Linux desktop environments 

The KDE, GNOME and Xfce implementations comply with the freedesktop.org Trash specification, ensuring that any applications written with this specification in mind will be interoperable with any trash can implementation.

Although the various Linux desktop environments such as GNOME, KDE, and Xfce provide a trash mechanism, there is traditionally no simple way to trash something from the command line interface. Some third-party applications, such as trash-cli, provide commands on the command-line to use the trash, compatible with the FreeDesktop.org Trash Specification.

macOS 
Using macOS, a file or folder is deleted in Finder by dragging its icon onto the Trash icon at the right hand end of the Dock, moving the item into the Trash folder, where it can be viewed but not used until it is moved out again. To restore highlighted items from the Trash to their original position, a contextual menu brings up a Put Back option. The keyboard shortcut to move highlighted items to Trash, or Put Back items, is . To finally delete files, clicking on "Empty" brings up a warning that this cannot be undone, and an option to delete.
   
Putting items in the Trash folder moves them to a hidden temporary folder: for the boot disk, a user account has this at /Users/username/.Trash/; each mounted volume such as an external drive has a hidden folder in the root folder named /.Trashes/. When viewing the device's available space the space occupied by the deleted files is shown as occupied. The Trash folder shows deleted files from external drives, including removable media. This does not apply to networked drives, where trying to move an item to Trash brings up a warning that it will be deleted immediately and this cannot be undone.

Since OS X El Capitan, the Trash can be bypassed by pressing  when a file is selected. Since macOS Sierra, the user can enable an option to have the Trash automatically empty after 30 days.

In UK and Australian English localisations, the Trash is known as "Bin".

Apps and iOS
In several macos apps and in the iOS mobile operating system, the trash facility is within apps rather than in the system as a central feature. The standard icon for Trash is a small version of the original Classic Mac OS trash can, and files are moved to a "Recently Deleted" folder within the app, where they remain available for recovery for a stated number of days, then are automatically permanently deleted. Apps where this applies include Photos and Mail. Files may still be recoverable if a computer backup was run before they  were moved to "Recently Deleted".

Microsoft Windows 

Microsoft's Recycle Bin is implemented as a special folder with columns like Date deleted and Original location. Typically only files deleted via File Explorer (but not necessarily other Windows graphical interfaces such as file selection dialogs) will be put into the Recycle Bin; files deleted via the Command Prompt are permanently deleted, as (by default) are files deleted via operating system APIs and applications other than Windows Explorer. Some operating system APIs do, however, allow applications to recycle files rather than delete them. In previous Windows operating systems and in MS-DOS, undeletion was the only way to recover accidentally or intentionally deleted files.

As standard, the Recycle Bin only stores files deleted from hard drives, not from removable media, such as memory cards, thumb drives, or floppy disks, nor does it store files deleted from network drives. There are methods to make it work on network paths, however.

The Recycle Bin has a setting to configure the amount of deleted files it can store. Free disk space allocated for this is not actually used until files are deleted from folders and stored in the Recycle Bin. In versions of Windows prior to Windows Vista, the default configuration of the Recycle Bin is a global setting for all drives to hold 10% of the total capacity of each host hard drive volume to store deleted files. For example, on a volume with a capacity of 20 gigabytes, the Recycle Bin will hold up to 2 gigabytes of deleted files. This can be changed anywhere from 0 to 100%  of the drive space, but will not be allowed to exceed 3.99GB of space, even if the user-indicated % of the drive space is larger than 3.99GB. If the Recycle Bin fills up to maximum capacity, the oldest files will be deleted in order to accommodate the newly deleted files. If a file is too large for the Recycle Bin, the user will be prompted to immediately and permanently delete the file instead.

The actual location of the Recycle Bin depends on the type of operating system and file system. On older FAT file systems (typically Windows 98 and prior), it is located in  Drive:\RECYCLED. In the NTFS filesystem (Windows 2000, XP, NT) it is Drive:\RECYCLER. On Windows Vista and above it is Drive:\$Recycle.Bin folder.

The Recycle Bin can be accessed from the desktop or Windows Explorer, or by typing "shell:RecycleBinFolder" in the Run dialog box (). It is the only icon shown by default on the Windows XP desktop. When accessed from the desktop, the Recycle Bin options and information are different from those of the physical Recycle Bin folders seen on each partition in Windows Explorer. From Windows XP onwards, with NTFS, different users cannot see the contents of each other's Recycle Bins.

Prior to Windows Vista, a file in the Recycle Bin is stored in its physical location and renamed as . A hidden file called info2 (info in Windows 95 without the Windows Desktop Update) stores the file's original path and original name in binary format. Since Windows Vista, the "meta" information of each file is saved as  and the original file is renamed to .

When the user views the Recycle Bin, the files are displayed with their original names. When the file is "Restored" from the Recycle Bin, it is returned to its original directory and name.

In Windows Explorer, files are moved to the Recycle Bin in a number of ways:
 By right-clicking on a file and selecting delete from the menu
 Selecting the file and pressing the delete key
 Selecting delete from the Task pane in Windows XP
 Selecting the file and choosing delete from the File menu (in Windows XP Explorer)
 By dragging and dropping a file into the Recycle Bin icon
 From the Send To menu
 From a context menu command or some other function in a software application (usually configurable)

It is possible to bypass the Recycle Bin and directly delete a file by holding the SHIFT key while performing an action that would normally send a file to the trash.

Other uses 
The 1984 original mac and several of its successors (up to the 1987 Macintosh SE) lacked a (then extremely expensive) hard drive, the system ran from a floppy disk which could be ejected () leaving its contents in memory, ready to transfer to another disk, and its icon was grayed-out ("ghosted"). In Classic Mac OS, dragging the disk icon to Trash (shortcut ) directly  ejected a disk (or CD) without leaving a grayed icon.

Mac OS X removed the transfer option, and dragging a disk or storage volume onto Trash converts the icon to the universal Eject symbol before unmounting and ejecting the disk or volume. This does not place the disk/volume in the Trash folder, nor does it erase the disk/volume.  and  have the same effect, and disk or volume icons in the Finder have an Eject icon beside them giving a simpler way to eject.

The GNOME Human Interface Guidelines cite using a waste basket to eject a removable disk as an example of a metaphor taken beyond its reasonable use.

See also 
 Xerox Alto
 File deletion
 Data erasure
 Temporary folder

References

External links 
 Microsoft Knowledge Base article "How the Recycle Bin Stores Files"

User interface techniques
File system directories

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