In this chapter, you have learned many ways to interact with SAS data sets from within the IML environment. You learned how to open and close a SAS data set, how to make it current for input and output, how to list observations by specifying a range of observations to process, a set of variables to use, and a condition for subsetting observations. You also learned summary statistics. You also know how to read observations and variables from a SAS data set into matrices as well as create a SAS data set from a matrix of values.