There are two variables that SAS automatically creates in the program data vector when processing a data step. One is _N_ and the other is _ERROR_. These are useful to know about when programming in SAS. Watch this video to learn about these variables, but only after you have learned about the program data vector and SAS' built in loop.

Although knowing about _N_ and _ERROR_ is useful, you don't need to know about these automatic variables to be an effective SAS programmer. So you can skip this video on your first trip through this learning module. There are some examples in this course where _N_ is used, so when you encounter those, you may wish to come back and watch this video.