Checkpoint: trace like the exam

You traced a 7-step loop by hand and predicted its output before running anything — the core exam skill. The pattern (i=1 o, i=2 ., i=3 #, i=4 ., i=5 o, i=6 #, i=7 o) came from the divisibility rules, not from luck: multiples of 3 are checked first, so 6 is # even though it is also even. The checkpoint asked you to encode the traced behavior: when you can both predict and reproduce, you own the concept. Next module: scaling this tracing discipline to methods calling methods, with real object state.