Thread: Question about sizeof()

I want to implement a package header for a client using a structure.

Code:

typedef struct header
{
        short ID;
        short opt;      //QR(1) Opcode(4) AA(1) TC(1) RD(1) RA(1) Z(3) RCODE(4)
        short QDCOUNT;
        short ANCOUNT;
        short NSCOUNT;
        short ARCOUNT;
} header;

it is posible that sizeof(short) to be different on various boxes? on mine is 2. The structure is always sum of sizes of the components inside the structure ?
Sorry if this question seems dumb!