[This self-explanatory example was sent to be by Bill Finke.]
#define Ob(x)  ((unsigned)Ob_(0 ## x ## uL))
#define Ob_(x) (x & 1 | x >> 2 & 2 | x >> 4 & 4 | x >> 6 & 8 |		\
	x >> 8 & 16 | x >> 10 & 32 | x >> 12 & 64 | x >> 14 & 128)

#define PORT_SYSCTLA  0x092         /* PS2 system control port A         */
#define SYSCTLA_DSK   Ob(10000000)  /* lights the fixed dsk activity led */
#define SYSCTLA_DSK0  Ob(01000000)  /* also lights fixed disk actvty led */
#define SYSCTLA_TMOT  Ob(00010000)  /* watchdog timer has timed-out      */
#define SYSCTLA_LOCK  Ob(00001000)  /* CMOS password area is locked      */
#define SYSCTLA_A20   Ob(00000010)  /* alternate address line 20 gating  */
#define SYSCTLA_RST   Ob(00000001)  /* alternate hot reset               */
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