For each process, the operating system maintains 2 integers with the bits corresponding to a signal numbers.

The two integers keep track of:

• pending signals
• blocked signals

With 32 bit integers, up to 32 different signals can be represented.

In the example below, the SIGINT ( = 2) signal is blocked and no signals are pending.

Pending Signals
31	30	29	28	...	3	2	1	0
0	0	0	0	...	0	0	0	0

Blocked Signals
31	30	29	28	...	3	2	1	0
0	0	0	0	...	0	1	0	0