In this lecture, we discuss how data sets are stored in libraries. There are two main types of libraries: temporary and permanent. Temporary libraries are located in a temporary folder in the computer's memory and the data stored there is lost once the session is closed. Permanent libraries are stored on the computer or server and the reference to the data is retained even after the session is closed. SAS provides sample permanent libraries, such as SAS Help and SAS User, which contain pre-made data sets that can be used for the coursework. To view the contents of a data set in a permanent library, it can be opened by double clicking on it. The data set's variables and observations will be displayed in a table, with character variables indicated by an icon and numeric variables indicated by a different icon. If a data set spans multiple pages, it can be accessed by clicking on the arrows at the bottom of the table.