What does the PUT statement do in a SAS DATA step?

The PUT statement in a SAS DATA step is primarily used to write data to an external file or to the SAS log. When employed, it determines how the data is formatted during the output process. This can include specifying a particular format for displaying numeric values, dates, or character strings, ensuring that the output is presented in a readable and useful manner.

For instance, when you want to output text or numeric values to a file or log, using the PUT statement allows programmers to customize the way these values are displayed. This can be crucial for clarity and for ensuring that the output meets specific requirements or standards.

In contrast, specifying how data is read into a dataset pertains to other statements like INPUT, which focuses on how raw data is brought into SAS for processing. Similarly, merging datasets does not involve the PUT statement but rather the MERGE statement. Filtering out missing values is typically managed through procedures like DATA step IF statements or using specific SAS functions, rather than with the PUT statement. Thus, the correct choice highlights the role of the PUT statement in defining the output of the generated dataset.