What is size_t in C?

Question

I am getting confused with size_t in C. I know that it is returned by the sizeof operator. But what exactly is it? Is it a data type?

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Answer 1

Since nobody has yet mentioned it, the primary linguistic significance of size_t is that the sizeof operator returns a value of that type. Likewise, the primary significance of ptrdiff_t is that subtracting one pointer from another will yield a value of that type. Library functions that accept it do so because it will allow such functions to work with objects whose size exceeds UINT_MAX on systems where such objects could exist, without forcing callers to waste code passing a value larger than "unsigned int" on systems where the larger type would suffice for all possible objects.