Common format of Gerber file used in PCB manufacturing:
The standard Gerber file format can be divided into rs-274 and rs-274x
Gerber file and aperture in rs-274 format are separate and different files.
The aperture of rs-274x format is integrated into Gerber file, so there is no need for aperture file (i.e., containing D code).
Data format: integer bit + decimal place
Common use: 3:3 (metric system, 3 integers, 3 decimal places)
2: 4 (English system, 2 integers and 4 decimal places)
2: 3 (English system, 2 integers and 3 decimal places)
3: 3 (English system, 3 integers and 3 decimal places)
Leading zero,trailing zero and non leading zero:
For example: 025690 leading zero becomes 25690 (leading)
025690 leads to zero and then becomes: 02569 (trailing)
025690 becomes: 025690 (none)
ENGLISH（inch or mil）
Gerber description is the circuit layer, and the graphics described are mainly copper parts. Or Gerber description is the solder mask, and the graphic description is mainly the solder mask.
Gerber description is the circuit layer, and the graph described is mainly copper free part. Or Gerber description is solder mask, and the graphics described are mainly non solder mask.
The layers described by Gerber are composed of different polarity layers. It is usually the superposition of excavation layer and positive layer. The polarity of excavated layer is C, which is mainly used for line protection or additional process data.