When I used ExpressPCB, you had to add the parts to the board yourself. EAGLE (and other, more-expensive, professional design programs) automatically build a schematic and a board at the same time. You have two windows open; and when you add a part to the schematic, it automatically adds it (off to the side) to the board as well.

Related, EAGLE (and other software) uses “ratlines” on the circuit board to indicate connections that exist on the schematic but still need to be routed on the board. Again, as soon as you add a connection on the schematic, EAGLE adds a ratline on the PCB directly from endpoint to endpoint, kind of a like a rubber band that’s connected to the two ends and will stretch a straight line from one to the other as you move them around..

You select the “routing” tool and click on a ratline you want to turn into a trace, and you can start clicking point to point to route it. You can leave off mid-way through and the ratline runs from the end of your routed section to wherever it’s supposed to go.

Also, automatically after certain operations and manually on demand, EAGLE will recalculate ratlines and move them to the shortest path between two nets. So it won’t always be your preferred path; but it’s pretty handy that you’re visually seeing a preview of the shortest set of connections that would get the job done.

Finally, EAGLE does have design and error check tools that will guarantee that the PCB matches the circuit, doesn’t have any yet-to-be-routed traces, and meets certain design rules such as minimum distance between traces, traces to pads, traces and pads to the edge of the PCB, etc.

I think that addresses everything you were asking; but if you have more questions, I’ll be happy to give them a shot.

I really like the ExpressPcb netlist schematic-to-board checker. Using this tool I never had an electrically incorrect board.

Do programs such as Eagle have this type of netlist check function. If not, what do they do to ensure your schematic compares electrically with the pcb?

Thanks,
Kip

Of course, another answer is to breadboard the circuit before you draw it, and build a prototype board afterward to see whether you drew it right . .&nbsp.