A signal is a small message that notifies a process that an event of some type has occurred. Each signal type corresponds to some kind of system event. Signals provide a mechanism for exposing these low$-$level events to user processes.

a$.(3$ points$)$ What does it mean for a process to $$catch$$ a signal? How is this accomplished?

b$.(3$ points$)$ What does it mean for a signal to be $$pending$?$ How many signals of the same type can be queued?

c$.(3$ points$)$ How does the kernel block pending signals? What are the conditions needed to do this?

d$.(5$ points$)$ How does an application block and unblock signals? What commands does it use? Why would it need to do this?