Data Sets SAS data sets are made up of two parts, the descriptor and data portions of the set. The descriptor portion has attribute information about the data set, such as the number of observations, the size and name of the variables, et al. The data portion contains the data described in the descriptor portion. Data sets are arranged in rectangular tables, where the vertical columns are called variables , and the horizontal rows are called observations . Each intersection provides the value of a variable, for that observation.
Variables are either numeric or character.
Character variables can be from 1 to 200 characters long. Missing values for character data are displayed as a space and missing values for numeric data are displayed as a period in any output generated by various SAS operations. In directory-based systems, such as UNIX and Windows, a library is defined as a collection of SAS files stored in a specific directory. Non-SAS files may exist in this directory. In directory-based operating systems, SAS assigns all file extensions automatically.