Drivers are the components that process ODBC requests and return data to the application. If necessary, drivers modify an application’s request into a form that is understood by the data source. You must use the driver’s Setup program to add or delete a driver from your system.
Data sources are the databases or files accessed by a driver. You use the ODBC Administrator to add, configure, and delete data sources from your system. The following types of data sources can be used:
| Data source | Description |
| User data sources | These are local to a computer, and can only be used by the current user. User DSNs are registered in the HKEY_CURRENT_USER registry subtree. |
| System data sources | These are local to a computer, rather than dedicated to a user. The system, or any user having privileges, can use a data source set up with a system data source. System DSNs are registered in the HKEY_LOCAL_MACHINE registry subtree. |
| File data sources | These are file-based sources that can be shared between all users that have the same drivers installed, and so have access to the database. These data sources need not be dedicated to a user or local to a computer. File data sources do not have a data source name, as user or system data sources do; they are identified by a file name with a DSN extension. |
User and system data sources are collectively known as machine data sources because they are local to a computer.
Each of these data sources has a tab in the ODBC Administrator that is dedicated to that type. For more information about data sources, see “Data Sources” in Chapter 3, “ODBC Architecture,” in the ODBC Programmer’s Reference.