Creating a c++ database program

I need to make a database program that doesn't rely on other DB engines like msjet so it can run on different platforms. It will mainly run on windows OSs. Is there any samples or if need be books on DB engine or algorithm
that manages its own file reading and writing to it the data entered and storing it in its own file. The file will just store text information. One question that i been wondering is if the program deletes an entry in the DB file will there be a "whole" there so the pogram has to shift all entries after the one deleted up one to fill it in so a file read next time  won't prompt an error in the file like corrupt. It seems DB files use one file and then add more data to it when creating a new record under that DB if so wouldn't the file get to big after a while. I came up with an idea that for the
DB file it would just be a directory and the "table" would be another directory in the DB directory. Under each table
will be individual files for each record that has the actual data. The header of the file will contain fields data that says how many fields and how far each field entry will be when reading out the file. Does this sound reasonable?