What does the LENGTH statement accomplish in a DATA step?

The LENGTH statement is used in a DATA step to define the storage length of a variable. This is important because it controls how much memory is allocated for that variable. For numeric variables, the default storage length is typically 8 bytes, but the LENGTH statement allows you to change this to optimize memory usage or manage data more efficiently. For character variables, you can specify the maximum number of characters the variable can hold. This can help in reducing the overall file size and improving performance when dealing with large datasets.

When you specify a length for a variable, it does not affect the data values that are stored; rather, it influences how much space is used in the data set. Proper use of the LENGTH statement can lead to more efficient data processing and faster execution of SAS programs, especially when working with large datasets.

The other options relate to different functionalities within SAS. For instance, setting display formats is handled by the FORMAT statement, adding new variables is accomplished through assignment statements or the SET statement with the OUTPUT statement, and specifying conditions for data exclusion would typically be done using WHERE or IF statements.