Gerber format

It began as the control language for Gerber Scientific's photoplotters and was essentially NC code: move here, expose, change aperture. One layer per file. The flaw in the original variant, RS-274-D, was that apertures were defined outside the file — the design shipped with a separate list that the fab keyed in by hand, and one misread line put wrong-sized pads on the entire run.

RS-274X, "Extended Gerber", moved aperture definitions into the file in 1998 and made it self-describing. Gerber X2 added attributes in 2014 that state what each file actually is — solder mask, copper layer, drill data — which until then had been a matter of the filenames happening to be sensible. Ucamco maintains the format, which has outlived both ODB++ and IPC-2581 for the dull reason that everyone already reads it.