MSDN Library was a library of official technical documentation intended for independent developers of software for Microsoft Windows. MSDN Library documented the APIs that ship with Microsoft products and also included sample code, technical articles, and other programming information. The library was freely available on the web, with CDs and DVDs of the most recent materials initially issued quarterly as part of an MSDN subscription. However, beginning in 2006, they were available to be freely downloaded from Microsoft Download Center in the form of ISO images.[4][5][6]