Gabriel Paubert wrote:
Really, the inch is by definition 2540µm, not the other way around since over 50 years ago.
As far as I know, 1" = 25400um, but I see your point ;-)
The only practical consideration I see is, that the internal unit of PCB allows handling with integer-arithmetic (makes comparisons a lot faster and safer than floating point). Assuming 32-bit signed numbers with 1/100mil this gives: 254nm resolution and +-545.46m coordinate range 32-bit signed and 1nm gives: 1nm resolution ;-) and +-2.147m coordinate range I don't know, if pcb really uses fix-point arithmetics, but even if not a reasonable internal unit has some importance. AFAIK with floating point, the average internal number should be around 1. HTH, Armin _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user