if-else and else-if Chains

A grade calculator needs an else-if chain because a score should land in exactly one bucket. If you write four separate if statements, each one gets checked independently, with no memory of what the others decided. A score of 95 is ≥ 90, but it's also ≥ 80 and ≥ 70, so all three of those separate ifs would fire, printing A, B, and C. Chaining them with else if links the branches together: once one condition is true, the rest of the chain is skipped entirely.

Here's the mechanism: the chain tests its first condition. If true, it runs that branch and jumps past everything else in the chain, including the final else. If false, it moves to the next else-if condition and asks again. This repeats top to bottom until something is true, or until every condition has failed, in which case control falls into the final plain else. Order matters enormously, because the chain commits to the FIRST true condition, not the most specific one. Put loose conditions first and tighter ones become unreachable dead code.

This topic sits right next to loops in the unit for a reason: both are about control flow that a trace table can capture one decision at a time. Where a loop re-asks the same condition pass after pass, an else-if chain asks a sequence of different conditions exactly once each, then stops. Tracing a chain means walking down the list, marking each condition true or false, and noting which single branch actually executes.