You are going to see a difference starting with the second time through the loop. When you use DO UNTIL ( total ge 200) the value of total does not change from the end of one iteration of the loop to the start of the second. But when you use DO TOTAL=100 to 200 (note that the increment amount will be 1 since it is not specified) the value of TOTAL is increased by 1 at the start of each new iteration.   Year Total In Total Out   Total In Total Out 1 100 103.75   100 103.75 2 103.75 107.6406   104.75 108.6781 3 107.6406 111.6771   109.6781 113.7911 4 111.6771 115.865   114.7911 119.0957 ... View more