Forward compatibility
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Forward compatibility is the ability of a system to accept input from later versions of itself.
Forward compatibility is harder to achieve than backward compatibility, since, in the backward case, the input format is known whereas a forward compatible system needs to cope gracefully with unknown future features. An example of forward compatibility is the stipulation that a web browser should ignore HTML tags it does not recognise.
Software applications attempting to provide backward compatibility with older operating system versions must pay close attention to the logic used in version detection. Often, a programmer will provide backward compatibility by detecting the earlier operating system version and providing special behavior for each version. Some applications error out when the operating system version cannot be detected, rather than default to the behavior corresponding to the most recent version. If the application has no tolerance for unexpected behavior, this may achieve the desired result at the expense of forward compatibility. If, however, the benefit of forward compatibility is greater than the risk of it not working, it is typically better not to error out in this case and to give the operating system a chance even if the version cannot be detected. The job of backward compatibility is often so difficult for operating systems that virtual machine emulation is often considered a solution for applications that have a dependency on prehistoric operating system versions.
- This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.