Autosave

Autosave is a function in many computer applications or programs which saves an opened document automatically, helping to reduce the risk or impact of data loss in case of a crash or freeze. Autosaving is typically done either in predetermined intervals or before a complex editing task is begun.

It has traditionally been seen as a feature to protect documents in an application or system failure (crash), and autosave backups are often purged whenever the user finishes their work. An alternative paradigm is to have all changes saved continuously (as with pen and paper) and all versions of a document available for review. This would remove the need for saving documents entirely.^[1] There are challenges to implementation at the file, application and operating system level.^[2]

For example, in Microsoft Excel 2003, this option is called AutoRecover and, by default, saves the document every ten minutes in the temporary file directory. Restarting Excel after crashing prompts the user to save the last recovered version. However, this does not protect users who mistakenly click "No" when asked to save their changes if Excel closes normally.

Mac OS 10.7 Lion added an autosave feature that is available to some applications, and works in conjunction with Time Machine-like functionality to periodically save all versions of a document. This eliminates the need for any manual saving, as well as providing versioning support through the same system. A version is saved every five minutes, during any extended periods of idle time, or when the user uses "Save a version", which replaces the former "Save" menu item and takes its Command-S shortcut. Saves are made on snapshots of the document date and occur in a separate thread, so the user is never paused during this process.^[3] Applications need to be updated to take advantage of this functionality, and a number of Apple's built in programs were updated with the release. Auto Save cannot be disabled in Lion.

Autosave is common in video games. Many video games have an autosave feature that saves progress during a session. For example, in an adventure game, it may auto save after completing a level or mission, or in fighting games, it might save after winning a match. Some games use autosave as the only method of saving data, and the player must complete a set amount of the game before saving takes place. Still another use of auto saving is as an anti-cheating device; for example in all MegaMan Battle Network games (except the first), the chip trader machines auto save upon giving out a new battle chip so the player can't cheat by soft resetting after each try of the chip trader until the desired chip is received.

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