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Concept Explainer
The ideas that are hard to picture from text alone, made visible. Pick one, change the inputs, and step through it.
Pointers and memory allocation: what it shows
The Concept Explainer has 6 explanations; pick one above and it opens on its own page.
Every variable is a box at an address. Step through a small C program and watch pointers point at boxes, malloc hand out blocks on the heap, and free give them back, including what goes wrong when a block is never freed or used after it was.