Assignment in Computer Science and Operating Systems
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ASSMNT_1538603725_1.docxImplement a Dispatcher for an OS. It will react to events and
change states of processes admitted to the system respectfully, as described in lecture notes and
the textbook. Events will be simulated. The sequence of events will be given in the standard
input (one event per line). Empty line will signify the end of the input. Format of one line is
as follows:
<time> <event> {<process id>}
where
<time>
is an integer number denoting local time in milliseconds measured from 0 (time will be strictly increasing from line to line);
<event>
is one of the following:
{
C - create
{
E - exit
{
R N - request resource number N
{
I N - interrupt from resource number N (request accomplished)
{
T - timer interrupt
<process id>
is a nonnegative integer, unique for each process (system idle process has <process id>= 0);
Here is an example of possible several first lines of the input (comments are here for explanation only):
100 C 1 \\ process 1 is created
200 C 2 \\ process 2 is created
250 R 3 2 \\ process 1 requests resource 3
300 C 3 \\ process 3 is created
400 T \\ timer interrupt
500 R 2 3 \\ process 3 requests resource 2
1000 C 4 \\ process 4 is created
1050 T \\ timer interrupt
1100 I 2 3 \\ interrupt from resource 2 (request of process 3 is accomplished)
1150 I 3 1 \\ interrupt from resource 3 (request of process 1 is accomplished)
2000 E 4 \\ process 4 exits
2100 R 2 2 \\ process 2 requests resource 2
2200 E 3 \\ process 3 exits
2300 R 2 1 \\ process 1 requests resource 2
3000 I 2 1 \\ interrupt from resource 2 (request of process 1 is accomplished)
1
3050 T \\ timer interrupt
3450 T \\ timer interrupt
3500 E 1 \\ process 1 exits
4000 I 2 2 \\ interrupt from resource 2 (request of process 2 is accomplished)
5000 E 2 \\ process 2 exits
Your Dispatcher will have to keep track of events and changes in the state of the processes,
taking into account the following additional conditions:
1) there are 5 dfÆerent kinds of resources in the system and requests can be serviced out of order
of arrival;
2) there is time sharing, so the process which is in running state is to be preempted as the resultof the timer interrupt if there are other ready processes in the system;
3) running process can also exit or get blocked because of request for a resource;
4) if there are no ready user processes, then process number 0 (system idle process) is running;
5) if process 0 is running and new process is created, or as the result of an event one of the blocked processes becomes ready (unblocked), this process will get CPU immediately.
When all lines of the input are processed, Dispatcher will print the following cumulative
information about all processes admitted to the system during simulation:
<process id> <total time Running> <total time Ready> <total time Blocked>
For the system idle process print only
<total time Running>
and assume that process 0 was created at time 0. The output is one line per process in the increasing order of process IDs.
For example for the input
100 C 1
200 C 2
250 R 3 1
300 C 3
400 T
500 R 2 3
1000 C 4
1050 T
1100 I 2 3
1150 I 3 1
2000 E 4
2100 R 2 2
2200 E 3
2300 R 2 1
3000 I 2 1
3050 T
3450 T
3500 E 1
4000 I 2 2
5000 E 2
2
expected output is
0 1300
1 750 1050 1600
2 1800 1100 1900
3 200 1100 600
4 950 50 0
