For an example-based introduction to using ODBC from C, refer to the Easysoft tutorial ODBC from C Tutorial Part 1.
Easysoft also recommend that you refer to the ODBC Programmer's Reference and other ODBC documentation provided on the Microsoft Web site.
A full Easysoft ODBC-ODBC Bridge installation includes some example ODBC applications written in C, PHP and Perl — see the ODBC-ODBC Bridge examples directory.