<P> The element pc consumes ten blocks of memory of the size of pointer to char (usually 40 or 80 bytes on common platforms), but element pa is only one pointer--sizeof pa is usually 4 or 8--and the data it refers to is an array of ten bytes (sizeof * pa = = 10). </P> <P> A union type is a special construct that permits access to the same memory block by using a choice of differing type descriptions . For example, a union of data types may be declared to permit reading the same data either as an integer, a float, or any other user declared type: </P> <P> The total size of u is the size of u.s--which happens to be the sum of the sizes of u.s.u and u.s.d--since s is larger than both i and f . When assigning something to u.i, some parts of u.f may be preserved if u.i is smaller than u.f . </P> <P> Reading from a union member is not the same as casting since the value of the member is not converted, but merely read . </P>

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