GDS II (also called "Stream" format) is used as an interchange between design systems and fabrication facilities. For information on reading and writing GDS, see Section 3-9-2 and Section 3-9-3, respectively. In GDS files, there are no names for each layer, just a pair of numbers (the layer number and type). It is important that Electric know how these values correspond with layers so that it can properly read and write GDS files. You can set the correspondences by using the GDS Map File... command (in menu File / Import) to read a GDS map file. You can also use the GDS Project Settings (in menu File / Project Settings..., "GDS" tab) to edit the GDS numbers and control other aspects of GDS input and output.
Figure 7.17

In the GDS Project Settings dialog, the list on the left shows all of the Electric layers in the current technology. By clicking on a layer name, its GDS numbers are shown in the top-right and can be edited. In addition to GDS numbers to use for layout, there are also two other types of GDS numbers: pin (for exports) and text (for export names).

Figure 7.27

These dialog elements apply to writing GDS:

You can also use the GDS Preferences (in menu File / Preferences..., "I/O" section, "GDS" tab) to control GDS input and output. For the difference between Preferences and Project Settings, see Section 6-3.
Figure 7.12

These dialog elements are available in the GDS Preferences: