When a FILENAME statement is used to assign a fileref to multiple raw data files, the list of files must be enclosed in a single set of parentheses. Each filename specified must be enclosed in quotation marks.

The FILEVAR= option enables you to dynamically change the currently opened input file to a new input file. The FILEVAR= variable must contain a character string that is a physical filename. Like automatic variables, the FILEVAR= variable is not written to the data set.

The DO statement creates the index variable x and assigns it the values of 8, 9, and 10. The assignment statement assigns the name of a raw data file to Readfile using the current value of x and the PUT function, which concatenates the values of x with the text strings c:datamonth and .dat. The COMPRESS function removes blank spaces from the values of Readfile.

The TODAY function returns the current date from the system clock as a SAS date value. The year number is then extracted from the current date using the YEAR function. The value of the current year, 2003, is assigned to y3. The year values 2002 and 2001 are assigned to y2 and y1, respectively. The PUT function concatenates the text string c:dataY with the year values and the text string .dat.

The END= option names a variable whose value is controlled by SAS. The value of the variable is 1 when you read the last record in an input file. Otherwise it is 0. You can test the value of the END= variable to determine if the DATA step should continue processing. Like automatic variables, the END= variable is not written to the SAS data set.

PROC APPEND uses the BASE= and DATA= arguments. BASE=SAS-data-set names the data set to which you want to add observations. DATA=SAS-data-set names the SAS data set containing observations that you want to append to the end of the BASE= data set.

If a DATA= data set contains variables that are longer than the corresponding variables in the BASE= data set, the FORCE option must be used with PROC APPEND. Using the FORCE option enables you to append the data sets. However, some of the variable values may be truncated in the observations that are read in from the DATA= data set.

You must use the FORCE option with PROC APPEND when the DATA= data set contains a variable that does not have the same type as the corresponding variable in the BASE= data set.

When the BASE= data set contains more variables than the DATA= data set, missing values for the additional variables are assigned to the observations that are read in from the DATA= data set.

The FORCE option does not need to be used if the BASE= data set contains variables that are not in the DATA= data set. The FORCE option must be used if