[1] The system records user actions and infers a generalized program that can be used on new examples.
Many PbE systems have been developed as research prototypes, but few have found widespread real-world application.
PbE is used in two independent clients for the BioMOBY protocol: Seahawk and Gbrowse moby.
The usual distinction in literature between these terms is that in PbE the user gives a prototypical product of the computer execution, such as a row in the desired results of a query; while in PbD the user performs a sequence of actions that the computer must repeat, generalizing it to be used in different data sets.
For final users, to automate a workflow in a complex tool (e.g. Photoshop), the most simple case of PbD is the macro recorder.