GDSII
Beginner
The standard file format that holds the drawing of every layer of a chip.
Novice
The standard file format for a chip’s layout, from Calma (1978). It is binary (written for programs, not people) and hierarchical: named cells hold shapes and references to other cells, and every shape carries a layer number and a datatype.
Expert
A stream of records, each with a 2-byte length, a record type and a data type. Coordinates are 4-byte integers in database units set by the UNITS record; reals use an excess-64 base-16 format, not IEEE 754. The original spec limits layers and datatypes to 0–255 and boundaries to 200 points.