The Data Access Layer

The DAL is responsible for persisting data, which is what programmers call loading and saving it someplace that won’t disappear when the user turns off the computer. (Remember that the actual data stores aren’t part of the layer.) When you separate the DAL from the rest of the application, you can easily change stores at any time. (And data storage technology tends to be pretty volatile--it’s an XML file today, and a SQL Server database tomorrow.)