You can decrement a DO loop by specifying a negative value for the BY clause. For example, the specification in this iterative DO statement decreases the index variable by 1, resulting in values of 5, 4, 3, 2, 1.

                                  V
     DO index-variable=5 to 1 by -1;
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     END;

When you use a negative BY clause value, the start value must always be greater than the stop value in order to decrease the index variable during each iteration.

                     start stop
                       V    V
     DO index-variable=5 to 1 by -1;
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     END;

Specifying a Series of Items

You can also specify how many times a DO loop executes by listing items in a series.

     DO index-variable=2,5,9,13,27;
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     END;

When the DO loop executes, it executes once for each item in the series. The index variable equals the value of the current item. You must separate each item in the series with a comma.

To list items in a series, you must specify either

• all numeric values

     DO index-variable=2,5,9,13,27;
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     END;

• all character values, with each value enclosed in quotation marks

     DO index-variable='MON','TUE','WED','THR','FRI';
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     END;

• all variable names.

     DO index-variable=win,place,show;
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     END;

Variable names must represent either all numeric or all character values. Do not enclose variable names in quotation marks.