>Gerber comes from the old machine that used to produce the films. It was
>a Gerber photoplotter. I'm not sure if they are still around or not. The
>old machines had an apeture wheel with various sized apetures, such as
>.030 round, .050 square, etc. The gerber format gives x,y coordinates
>and a tool number, with directions to "flash", or to "draw" to another
>set of x,y coordinates. Typically it has a corresponding apeture list
>equating tool numbers to physical apeture shape/size. Newer units still
>use this information, but rasterize it all like a laser printer and
>transfer the image to a film. There is also a newer, more sophisticated
>Gerber format, (I forget the number), that can contain "macros" or symbol
>blocks of instructions for repeating patterns. Check out IPC's site,
>I think
http://www.ipc.org for more info. Most pcb design packages produce
>Gerber files, this is what you send to your board house to get boards
>made, along with an Excellon file of drill information. At one time
>there was and add-on for AutoCad that allowed one to do these type of
>things, and several years ago, before I got a real pcb package, I wrote a
>set of macros for Generic Cadd, and a conversion program that would allow
>some primitive pcb design functionality.
>
>Stew Benedict
>
>
