### Sizeof() Operator Data Type

The sizeof() operator returns the size of a variable or type in bytes. The data type of this size is size_t, which the compiler declares in the file stddef.h. If your source code assumes that sizeof() returns a number of type int, it might not work correctly.

NOTE The compiler evaluates the value returned by sizeof() only at compile time, not runtime.

NOTE The sizeof() operator is not intended to work in preprocessor #if/#elif directives.