sizeof bit-fields

[Massimiliano Cialdi <cialdi@xxxxxxxxxxx>]

I tried to declare a bit-filed in this way:

struct rec
{
	unsigned short a : 10;
	unsigned short b : 10;
	unsigned short c : 10;
	unsigned short d : 10;
};

40 bits = 5 byte.
but sizeof(struct rec) is 8.

How can I obtain a 5 bytes long structure (if it is possible)? 

thanks
-- 
Massimiliano Cialdi
cialdi@xxxxxxxxxxx
m.cialdi@xxxxxxxx