What does the '@@' line-hold specifier accomplish in SAS?

The line-hold specifier '@@' in SAS is used to retain the values from the current line of data input for subsequent iterations of the DATA step. When you use '@@', SAS does not advance to the next line of the input data until it reaches the end of the current DATA step iteration. This allows you to read multiple records from the same line of input.

For example, if your input data consists of several pieces of information on a single line that you want to process together, using '@@' will let you hold that line and read additional values from it before moving on to any subsequent lines of data. This is particularly useful when working with data in a format where multiple records are supplied on the same line, allowing for efficient data handling.

The other options do not accurately describe the functionality of the '@@' specifier. The line-hold specifier does not release the line at the next iteration, signal the end of input data, or prevent line-holding. Instead, it effectively extends the reading from the same line across multiple iterations, making it a powerful tool for managing data input in SAS.