This section describes alternative signal handling functions derived from BSD Unix. These facilities were an advance, in their time; today, they are mostly obsolete, and supported mainly for compatibility with BSD Unix.
There are many similarities between the BSD and POSIX signal handling facilities, because the POSIX facilities were inspired by the BSD facilities. Besides having different names for all the functions to avoid conflicts, the main differences between the two are:
intbit mask, rather than as a
The BSD facilities are declared in signal.h.