What is the function of the line-hold specifier '@' in SAS?

The line-hold specifier '@' in SAS serves the purpose of holding the current line of data for multiple iterations of the DATA step. This means that when the line-hold specifier is used, SAS does not automatically advance to the next line of data after processing the current line; instead, it retains the contents of the current line for further processing.

Using the line-hold specifier is particularly useful when you need to parse or manipulate multiple variables from the same line across several statements. For instance, when reading data that spans multiple lines or when performing conditional logic that depends on the same line's values over various iterations, the line-hold specifier enables this type of functionality. Continuing to hold the line allows the programmer to extract or perform calculations on variables without moving to the next record.

In scenarios where you might want to check additional conditions or make calculations based on the same set of data, the line-hold specifier is invaluable. This functionality aligns perfectly with the behavior of holding onto the line data, showcasing its critical role in data manipulation and control flow within the SAS programming environment.