Overview

Forward annotation is the process of updating a layout to reflect changes made in the schematic. This process is used when, for example, a new component is added to a schematic and needs to be included in the layout. This section describes how to forward annotate changes in a gEDA schematic to a Pads PowerPCB layout.

Pads implements forward annotation through the use of an ECO (Engineering Change Order) file. The ECO file describes the differences between a current design and the desired design. Pads generates the ECO file by performing a netlist comparison between a new netlist file and the netlist contained in the current layout.