[JoeAltmaier]

Embedded can be almost anything, C/C++/java and so on. I've seen microcontrollers with 8K of program space, written in C++. Why? Because it optimizes better than the 'C' programmer does.

Unions are used for interpreting any kind of record stream. Reading serialized binary objects from a file? Use a union. Network packets? A union.

[MereInterest]

When reading from a binary source, I've seen that, instead of unions, the char pointer will be cast to a pointer to the appropriate data structure. What is the advantage of using a union instead of casting?

[theseoafs]

Well, for one, unions have defined behavior in C, while passing pointers around and casting them randomly doesn't.

I don't know if this is the best example. Generally you see unions in C to cover "tagged unions", I.e. Those things that would be subsumed by algebraic data types in other languages.

[MereInterest]

Ah, got it. I am used to C++, where accessing the non-active member of the union is undefined behavior. Thank you.

[stephencanon]

The usual way to do this via memcpy, rather than either a union (requires some non-portable extension like "packed") or pointer casting (invokes undefined behavior if alignment isn't satisfied).