This book comprehensively documents essential concepts for SAS features, the DATA step, and SAS files. Topics include basic SAS concepts such as SAS processing, SAS names, missing values, expressions, time and date values, WHERE-expression processing, SAS output, and error processing and debugging; SAS DATA step concepts such as DATA step processing, reading rawdata, combining and modifying SAS data sets, BY-group processing, array processing, and creating and using stored compiled SAS programs; and SAS file concepts such as SAS data libraries, SAS data sets (SAS data files and SAS data views), indexes, file protection, SAS I/O engines, SAS file management, and external files.