General Reading External File Existing

What is the difference between reading data from an external file and reading data from an existing data set?   

Deepika Kaif
@[email protected] | Updated 23 Dec. 2018

 The main difference is that while reading an existing data set with the SET statement, SAS retains the values of the variables from one observation to the next. Whereas when reading the data from an external file, only the observations are read. The variables will have to re-declared if they need to be used.