@Tacoma66 wrote: Thanks for the reply.   Yes, those are the basics,   but why why would a programmer save x from y and then turn around and create a new y (same name) from the x you just created.   y is already in the work library...   I've seen this done in several legacy programs I am working on, and I don't know why the programmer is doing it. I've seen it with work lib only sets. There are people out there that create a new data set every time they do a calculation or add a variable instead of moving the code (once tested) to an earlier data step.   You will find dozens of examples on this forum of people with code like: data temp; set sashelp.class; run; proc print data=temp; run; instead of Proc print data=sashelp.class; run; Normally I consider it behavior of new programmers that just haven't learned better. There are some things I see that make me think there are class Instructors that just never learned better because of some recurring code with same named variables/datasets and code like you are asking about that we see here every fall and spring. ... View more