Which attribute controls the format of a variable during a PROC step?

The correct choice relates to the specific scenario in which various attributes can be applied to variables during a PROC step. In SAS, while several attributes can influence how data is represented, attributes that specifically control the format of a variable within a PROC step are ones assigned during that particular PROC execution.

When working with PROC steps, formatting can directly impact how output is displayed, such as controlling the decimal places for numerical values or defining the appearance of date variables. This formatting can be done on-the-fly, meaning it is applied specifically for that PROC step and will not change the underlying dataset or persist outside that particular execution of the PROC.

In contrast, other answer choices do not properly capture this nuance. Attributes that are permanently assigned will affect how variables are handled across different data steps and PROC steps. Temporarily assigned attributes in a DATA step don't carry over into PROC steps unless explicitly defined there. Lastly, attributes assigned in the data set descriptor portion pertain to the overall structure of the dataset rather than focusing specifically on the nuances of output formatting during individual PROC operations.