Basic operations with the SharePoint .NET client object model

When you create an App for SharePoint 2013 project in Visual Studio 2012, references to the .NET Framework assemblies,Microsoft.SharePoint.Client.Runtime.dll and Microsoft.SharePoint.Client.dll, are automatically added to the project.

The files are located on any SharePoint 2013 server at %ProgramFiles%\Common Files\Microsoft Shared\web server extensions\15\ISAPI.