Control Structures: IF, SELECT, DOW, DOU, and FOR

Every branch and loop in a program is built from five patterns: choose among a few conditions, choose among many discrete values, repeat while a condition holds, repeat until a condition is reached, and repeat a known number of times. This lesson covers the RPG structure for each —…

What you'll be able to do

1. 1Write branching logic using IF/ELSEIF/ELSE, and select the appropriate number of branches for a given business rule.
2. 2Use SELECT/WHEN as a clearer alternative to a long ELSEIF chain when testing a single value against multiple discrete conditions.
3. 3Distinguish DOW (pre-test) from DOU (post-test) loops, and choose the correct one based on whether the loop body must execute at least once.
4. 4Construct a FOR loop with explicit start, end, and step values, and identify when it is the more appropriate choice over DOW or DOU.
5. 5Apply LEAVE and ITER to control loop flow explicitly, and weigh the readability trade-offs of using them against restructuring the loop condition.