The "int sem$\_$trywait $($sem$\_$t $*$sem$)"$ operation blocks if

$($a$)$ the semaphore value $>0$

$($b$)$ the semaphore value $=0$

$($c$)$ it never blocks

$($d$)$ None of the above

Which of the following CORRECT about the sem$\_$init function shown below.

int sem$\_$init$($sem$\_$t $*$sem$,$ int pshared, unsigned int value$)$;

$($a$)$ It is used to initialize both named and unnamed semaphores and to assign the value

specified by the "value" parameter to the semaphore.

$($b$)$ It is used to initialized named semaphores only and to assign the value specified by the

"value" parameter to the semaphore.

$($c$)$ the pshared variable is used to specify whether the semaphore can be used within the

calling process only or it can be used by multiple processes.

$($d$)($b$)$ and $($c$)$

$($e$)$ None of the above

In the pseudo$-$code blow, what initial values of the semaphores $S$ and $Q$ will cause the two pro$-$

cesses to alternate in executing their printf statements such that the output is A $,$ B$,$ A$,$ B$,$ A $,$ B$,$ A $,$ B$,...$

$($a$)S=0,Q=0$

$($b$)S=1,Q=1$

$($c$)S=0,Q=1$

$($d$)S=1,Q=0$

$($e$)$ None of the above