[Shapelib] Mapping latitude and longitude to shapefile

[Yasir Malik]

Hello,
We are making a GPS device for the Game Boy Advance.  We plan to have 
auto mapping.  Our ESRI shapefiles are downloaded from MapShots.com. How 
can we (1) use longitude and latitude coordinates to select the proper 
shapefile and (2) map the latitude and longitude coordinates 
onto the shapefile?

Thanks,
Yasir