Boolean Variables and Flags

A loop only sees one element at a time, so it has no memory of what happened three iterations ago unless you give it one. A flag is a boolean variable, often started as false, that you flip to true the instant the condition you care about becomes true. Once it is true it just stays true, quietly carrying the answer forward through every remaining pass of the loop, until you finally ask about it with an if statement after the loop finishes.

The mechanism is just an assignment sitting inside an if inside the loop. Each pass checks the current element; if it matches what you are watching for, the flag gets set to true. Nothing resets it on the next pass, because reaching into the past is exactly the point. If you are only checking for one occurrence, you never need to set it back to false inside the loop.

This connects directly to the rest of unit 2 because a flag is really just a condition's result given a name and a lifespan longer than one line. Where you declare and reset the flag matters as much as where you set it true: initialize it before the loop that tracks it, and only reset it if you genuinely want to forget the past, such as starting a fresh check on a new array. Mixing this up is the most common source of logic bugs with flags, and it sets up later topics like nested loops and string processing, where a flag often reports back on an entire inner loop at once.