• When a signal handler begins, the bit in the signal mask for that signal is cleared.

• While in a signal handler for a signal executes, that signal is blocked until the signal handler returns. So 1 or more signals of the same kind are sent to a process while it is in the signal handler, only 1 will be observed.

• If a "slow" system call such as a file read is interrupted by a signal, we would want the read to resume.

The standard signal function to register handlers may work this way. For portability, a wrapper function can be used that is implemented with newer POSIX compliant functions.