An array is a fixed sequence of elements of the same type, laid out back to back in one contiguous block of memory. Because every element takes the same number of bytes, the array only needs to remember its starting address and its length.
The values sit next to each other in order, with no gaps and no pointers linking them. A five-element integer array is just five integers packed tightly, one after another.
Reading nearby elements is fast, since the CPU pulls in whole cache lines at once. The cost is rigidity. The block is one piece, so you cannot cheaply grow it in place when neighboring memory is already taken.
Rewriting in plainer words…
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An array is a fixed sequence of elements of one type, stored back to back in a single contiguous block of memory.
Every element takes the same number of bytes, so the array only has to remember where it starts and how many elements it holds.
Nothing sits between the elements and no pointers link them, so a five-element int array is just five ints packed in a row.
Reading nearby elements is fast because the CPU pulls in a whole cache line at a time, so the next few elements are already loaded.
The cost is rigidity, because the block is one piece and you can't cheaply grow it in place when the memory next to it is already taken.
Weak answers to avoid
Stops at 'a list of values'That skips the memory half of the question. Say it is one contiguous block of same-size elements, tracked by a start address and a length.
Says arrays grow on their ownThat describes a dynamic array. The block itself is fixed, and growing it usually means allocating a bigger one and copying the elements over.
Describes elements linked by pointersThat is a linked list. Array elements sit side by side with nothing linking them, and that is why index math and cache-friendly scans work.
Gives only the upsideLeaving out the cost sounds one-sided. Say that one fixed block can't cheaply grow in place when the memory next to it is taken.
Interview lens
Likely follow-ups, what you can say, and the weak answers to avoid.
