The DOS file which contains the permanent SAS data set is named and written automatically by SAS when the DATA statement is executed. SAS gives the physical file the DOS name datasetname.sd2 . The SET statement is used after the DATA statement. It employs exactly the same data set naming conventions as the DATA step and can be used for any combination of permanent or temporary SAS data sets. A SAS variable name must begin with a letter and can be no more than eight characters long.
Numeric variables represent numbers and can be input only as numerals.
Numeric is the SAS default data type. Character variables contain letters or other non-numeric data or numeric data to be treated as characters. To indicate a variable's column location, write its first possible column, a dash, and its last column. Another method of entering raw data is by listing variable values without their respective column locations. It is called list-format input.