When using the PUT function, which option is required?

The PUT function in SAS is used to convert a variable's value into a formatted character string. The source variable is essential because the function requires an input value to begin the formatting process. Without a source variable, the PUT function cannot perform its intended operation since it has no value to convert into a string format.

While options related to the output dataset name, numeric format, or character length may be relevant in other contexts or advanced usages, they are not required by the PUT function itself. The fundamental purpose of the function is to take a source variable, apply a specified format (if needed), and produce a formatted character string. Thus, having a source variable is the foundational requirement for the successful operation of the PUT function.