With the release of Visual Basic 2.0, developers were introduced to a new method for accessing data,known as Data Access Objects (DAO). This was Microsoft’s first attempt to create a data consumer API.Although it had very humble beginnings, and when first released only supported forward-only operations against Odbc data sources, it was the beginning of a series of libraries that would lead developerscloser to the ideal of Universal Data Access. It also helped developers using higher-level languages such as Visual Basic to take advantage of the power of ODBC that developers using lower-level languagessuch as C were beginning to take for granted.

DAO was based on the Jet Engine, which was largely designed to help developers take advantage of the desktop database application Microsoft was about to release, Microsoft Access. It served to provide another layer of abstraction between the application and data access, making the developer’s task simpler.
Although the initial, unnamed release with Visual Basic 2.0 only supported ODBC connections, the release of Microsoft Access 1.0 marked the official release of DAO 1.0, which supported direct communication with Microsoft Access databases without using ODBC. Figure below shows this relationship.

DAO 2.0 was expanded to support OLE-DB connections and the advantages that come along with it. It also provided a much more robust set of functionality for accessing ODBC data stores through the JET Engine. Later, versions 2.5 and 3.0 were released to provide support for ODBC 2.0 and the 32-bit OS introduced with Windows 95.

Drawback

The main problem with DAO is that it can only talk to the JET engine. The JET engine then communicates with ODBC to retrieve the data. Going through this extra translation layer adds unnecessary overhead and makes accessing data through DAO slow.