According to Wikipedia is a contingency option, meaning something is used when your original choice is not available by some reason.

This is a generic definition that is good for computing. Of course in each context it may have a more specific meaning. But it always has that basis. And it is used in a very diverse context (general infrastructure, project management, software development, configurations, algorithms, data structures, tests, specific technologies, etc.), some are even in technology specifications.

The translation is just contingency or plan B .

There is not much secret, no rules, nothing. It is only to have an option chosen automatically when the principal is not present or available for some reason. Note that the unavailability may be momentary or even selected by some specific criteria according to the will of the software maker, probably following certain requirements.

Note that this is different from having a default option where you have something chosen and only if it is explicitly chosen is another that changes the option. The fallback occurs automatically and the noun is the opposite of default , which is not the default.

Examples

An example is a running environment that tries to use a native option, not having it available it tries to emulate execution (rendering something, compiling, etc.).

There are cases where the term can be used for backup options, such as a database that takes action when another fails, but this usage is less common.

There is a lot of talk about fallback when using web technologies where a feature may not be available in a browser. You can even marking to indicate contingency .

But it can be extended to any technology. It has use when multiple versions are available and one is preferred, but others may suit as well.

I will not mention examples of hardware, networks, etc. because it is not our focus, but it is where it occurs very often to give more reliability.

Rollback

The only relationship is that the two end with back . This term is the action of going back, undoing what has been done and returning to the original state. Usually because of a crash, but can be by choice.

Fallback is an option to use if the preferred option is not available.

The role of fallback is to increase the reliability and availability of systems.

In the case of software, it is a structuring scheme that allows the processing of program, data or process errors. Usually (but not exclusively) involves data restoration, state restoration, or continuation of execution. Some practical examples:

• Rendering 3D graphics via software if your computer does not have video accelerator, graphics card, or Library Library
• The Android Environment APIs Contingency System (applications written for modern APIs can run on devices older)

On the other hand, Rollback (or restore )) is one of the possible actions to take in the case of a fatal environment error, given or status. It means restoring the state of your application to an earlier, more stable and functional one.

Fallback means "plan B" or emergency plan, ie if the configuration set by the programmer fails there will still be a default option that will assume a valid value.

It has no correspondence with the term rollback.

The very description in English responds.

  

| The fallback locale The locale to use when the current   one | is not available. You may change the value to any   of | the language folders that are provided through your application.

As described, a custom sewing may not be possible, so it "falls back" to the default seam.

An example, when trying to get the user's browser language and may not be able to get the value, a default fallback is made.

Fallback specifies which file to use if it tries to access a file that is not stored.

Fallback is different from Rollback .

Rollback is a term used to restore data to a condition that was previously saved, such as a restore from a backup.
Fallback is somewhat more comprehensive, as it is a term used to designate the planning with the procedures required to restore a system back to operational condition.
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Fallback is not, in general, a technical term in computing. It is used according to its general meaning, "contingency" or "secondary alternative."

Rollback is a well-established technical term, especially in database, when you have a transaction and at the end commit or the rollback .