The do loop
DO index=1 to 5 by 2;
x=index;
end;
tells SAS to
Assess INDEX at the top of the loop to see whether index satisfies the condition needed to run another iteration.
Increments INDEX by 2 at the bottom of the loop.
So when index=5, the loop runs an iteration (and x=5). At the end of that iteration INDEX is incremented to 7, then SAS goes to the top for assessment of index. It exceeds 5, so the do loops are finished, leaving X=5.
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