Comp111 - Quiz 1 Answers
Oct 7, 2015 - closed book
Please fill in the blanks. Each blank is worth 5 points.
Blanks with the same number have the same answer.
- In ____round-robin____ scheduling, the goal is to allot
equal amounts of time to all runnable processes, while in
____batch____ scheduling, the goal is to accomplish as
much computation as possible. In ____real-time____
scheduling, the goal is to respond to external events as quickly as
- The ____fork_______ system call creates an exact copy
of a process, that differs only in the ____return value_______ of
____fork____. The execl system call runs a
new process; it erases current ____memory____ but
preserves ____environment variables____ and open
____files____. After a child process ends, the parent
can call ____wait____ to reap the exit code from the
process. This can be done in response to the signal
- More generally, a process communicates with the operating system
via system calls, that in turn communicate with device
____drivers____ when necessary. These, in turn, manage
device ____state____. When a device needs attention
from a process, it sends a ____signal____ to the
- Processes can communicate via ____pipes____ that
are essentially first-in, first-out character queues. These are
____preserved____ when a process duplicates itself, and
one can use the ____dup____ system call to remap the
standard input and output for the process. To do formatted I/O, one
can use ____fdopen____ to obtain a file pointer from
each file descriptor. A common danger in using file pointers is to
forget to ____flush____ a file pointer, leading to
output never being sent. This is not a problem for file descriptors,
because writes to them are not ____buffered____.
- The state code ____D____ in status
corresponds to "uninterruptable" wait, which is different than
sleeping only because the scheduler is not permitted to stop it.
- (Extra Credit) When the operating system doesn't want to know
about a type for any reason, it declares variables of that type as
____void *____ in system calls.