This page is about Eagle¹⁾ Cadsoft, a computer program which helps designing schematic diagrams (schematics) and circuit boards (pcb)²⁾.

During a design process it is sometimes necessary to add components which are not available in the ready supplied libraries. For this, components can be created manually and imported in the design. The method for this requires some fundamental understanding how components are organized in Eagle, both in the application itself as on the file structure. Guidelines about library design and some criteria about a consistent nomenclature should help a user to successfully manage such components, upgrade or extend them with other packages, ultimately to keep a good overview.

In the Control Panel within Eagle, one or more library folders may contain libraries with a long list of IC manufacturers, group of generic components or group specific symbols which can be browsed through.
When opening an existing library³⁾, one will observe that an item in such a library has for each device breed (i.e. equivalent components sharing the same functions but having different packages and/or symbols) three entities primarily:

• device: The real component, residing in a specific package with a specific symbol
• package: Footprint in the layout
• symbol: Drawing in the schematic

Each of these three entities characterize a specific aspect of a component residing in a library, either directly or within a group of a component breed.