A macro that squares a number — what could go wrong? Everything, because the preprocessor doesn’t square numbers; it pastes text. This question from our C Programming Quiz App is the canonical macro trap, the one that turns SQ(2 + 3) into something that isn’t 25 — and the reason every style guide screams “parenthesize …

Two variables, one name, one program. When an inner block declares its own x, what happens to the outer one — replaced, modified, or just… hidden? This question from our C Programming Quiz App tests variable shadowing, the scope rule that decides which x each printf can see. The Quiz Question int x = 5; …

The switch matched case 5 — so it runs case 5’s code and leaves, right? Not in C. This question from our C Programming Quiz App is about fallthrough, the single most surprising rule of the switch statement, responsible for decades of bugs and one legendary telephone-network outage. The Quiz Question int x = 5; …

continue and break both bail out of something — but out of what, exactly? Mixing them up changes a loop that skips one item into a loop that abandons everything. This question from our C Programming Quiz App pins down what continue skips, what it doesn’t, and the one loop where it behaves differently than …

The loop starts at 0 and the condition says “less than 3” — so it prints 0, 1, 2. Right? Wrong, and by two different one-off errors at once. This question from our C Programming Quiz App puts a post-increment inside a while condition, where its when-does-it-happen semantics decide both the first value printed and …

x is 10 — clearly not zero — yet this if doesn’t do what it looks like it does. One missing = turns a comparison into an assignment, and it’s arguably the most famous typo in C. This question from our C Programming Quiz App checks whether you can spot it — and whether you …