Question

As I know C enum is unsigned integer, but this may vary by implementation.
What type should I use for the enum in binary representation?

*PS
‘binary representation’ means byte-array. I want to serialize enum values to socket to inter-operate with other programs.

Answer 1

It’s up to the compiler to use an int to represent an enum type, or a long if an int is not sufficient to hold all the values of the enum.

If you know that all your enum values can be represented by an int, then you can safely use int as the binary representation of your enum values.