Filter is a device or process that removes from a signal some unwanted component or feature.

Filtering is a class of signal processing, the defining feature of filters being the complete or partial suppression of some aspect of the signal. Most often, this means removing some frequencies and not others in order to suppress interfering signals and reduce background noise. However, filters do not exclusively act in the frequency domain; especially in the field of image processing many other targets for filtering exist.


  1. It also has uses in flow compilers.

    (We can parse input language into data structure, apply flow net [perhaps with filters] to transform it then generate output in target language).

  2. Crossbreeding software (making complex part [atomic operation consisting of few operations] from many filtered parts) is an option.