When you install Composite C1 you have your data (content) persisted in XML files by default. You can easily migrate to SQL Server, but XML should work fine for your sake.
You can manipulate data from code - see http://docs.composite.net/Data/Adding-pages-with-Csharp as an example and http://docs.composite.net/Data in general. All content in Composite C1 can be read and updated via the data API, including data types you create yourself.
You can also use C1 Packages to roll in data - see http://www.composite.net/Add-on-Market/Packages/Composite.Tools.PackageCreator - this would allow you to add data to a package which you then then install on a new site. Our starter sites are packaged using this thing.
You could also go directly on the XML data files or SQL Server tables, but using the APIs is definitely a better call.
You can manipulate data from code - see http://docs.composite.net/Data/Adding-pages-with-Csharp as an example and http://docs.composite.net/Data in general. All content in Composite C1 can be read and updated via the data API, including data types you create yourself.
You can also use C1 Packages to roll in data - see http://www.composite.net/Add-on-Market/Packages/Composite.Tools.PackageCreator - this would allow you to add data to a package which you then then install on a new site. Our starter sites are packaged using this thing.
You could also go directly on the XML data files or SQL Server tables, but using the APIs is definitely a better call.