Description
1. (20pts) Where (initilized data segment, stack, or heap) are variables
a, b, *b, and c defined in the following code are stored, respectively?
int a;
main()
{
char *b;
char c;
b=(char *)malloc(10);
}
2. (50pts) Suppose there are two jobs, each of which is composed of three
steps as described in the following and are submitted simultaneously
to a computer with a single CPU:
Job 1 is composed of:
step 1 — a computation needing 45 seconds of CPU time,
step 2 — an I/O operation needing 45 seconds of I/O operation time,
and step 3 — a computation needing 45 seconds of CPU time.
Job 2 is composed of:
step 1 — a computation needing 54 seconds of CPU time,
step 2 — an I/O operation needing 54 seconds of I/O operation time,
and step 3 — a computation needing 54 seconds.
Question:
What is the total time needed to complete these two jobs when the computer
executes the jobs with (i) the mono-programming approach, and (ii)
the multi-programming approach, respectively?
Assumptions:
-The time for the CPU to process any interrupt is 0, and the time for job
scheduling (i.e., the time for swapping out the job currently run by
the CPU and loading in another job for the CPU to run) is also 0.
-I/O operations are performed on different I/O devices; hence, multiple
I/O operations can be performed in parallel.
-Interrupted programs will be resumed in the same order as they have
been interrupted.
3. (30pts) Briefly describe how the following types of resources should
be protected?
-I/O devices
-Memory
-CPU
