The Excellon format is a format used to drive CNC drilling and routing machines in electronics manufacturing of printed circuit boards (PCBs). It is a variant of the EIA RS-274-C standard.
It is an ASCII format consisting of commands to drill holes of specific diameters at specific locations on a PCB. A sample file:
The name Excellon format is derived from the Excellon Automation Company, which was market leader in PCB drilling and routing machines during the 1980s, and whose NC format became widely used.
The IPC organization defined a standard for NC files, the IPC-NC-349 format, which is similar to the Excellon format.
Read more about Excellon Format: Usage, Excellon-like Files