Use sizeof. That's what it's there for! Bearing in mind that structs often incorporate padding, it's not easy to find their size. I suppose you could initialise an area of memory to 0x00, write a struct over it, and see which bytes contain bits that have changed; then do the same but initialising to 0xff; then deduce the size of the struct from the results. But it's much easier and more reliable to use sizeof.
David
