GPS Chart CD or chip

[Nautically Challenged]

I am buying a Garmin 178C GPS. I would like to buy the chart on CD but I don't know how to download the data on a chip. Can I do it with my computer and how?
Pre-programmed chips sell for the same price but they only have information for a small area. For instance, the chip offered for South Florida contains chart from Jacksonville to Key Largo at the same price as a CD that contains data for the whole US.
What's the best way to go?
Thanks

 

[L Hall]

Yes, that is the case. The CD includes one unlock code. You have to buy additional unlock codes for other areas. And you also need to buy blank cartridges.

 

[Silverton_34]

I have one chip for the West Coast of Fla and another for the entire U.S. East Coast. This works for me. I change chips at Clewiston, Fla where I stay overnight.