The COLUMNS= suboption places DATA step variables into columns that are defined in the table definition. For instance, the first column-specification specifies that the first column of the output object contains the values of the variable YEAR and that it uses the column definition named char_var. GENERIC= must be set to ON, both in the table definition and in each column assignment, in order for multiple variables to use the same column definition. 
        columns=(
           char_var=year(generic=on)
           char_var=country(generic=on format=$cntry.)
           char_var=type(generic=on)
           num_var=kilotons(generic=on format=comma12.)
           )
        );