How to calculate average waiting time of Round robin scheduling

did you understand the partial solution (the actual schedule) you have posted?

Waiting time of a process = finish time of that process - execution time - arrival time

Once you have this for all process then just take the average. That would give you the avg waiting time of the scheduling algorithm for this instance

More details:

Here process p1 did not wait for the first 8 seconds. Then at t=9 it was preempted. It was in wait mode from time t=9 to t=29 while process p3 was executing. So p1 had waited for 21 seconds while p3 was executing. At t=29, p1 started again and completed at t=33. In total, p1 had waited for 21 seconds. As per the formula we get waiting time as 33-12-0=21. Basically for each process we look at the time between when it arrived and when it finished. Any time between this interval when it is not executing is a wait time

I'm sure there are many bugs (starting with not caring if the user wants to enter 11 or more processes even though your array of processes is limited to 10).

However; I spent 10 minutes trying to decipher your code and still don't really know what it thinks it's doing - there's no comments at all and the variable names and function names don't help (e.g. no is not a boolean "yes/no" variable, checkprocess() doesn't check one process but checks all processes to see if all processes have finished, etc). Mostly, if I were being paid to fix this code I'd simple throw it out and rewrite it from scratch to save time. I thought about rewriting it from scratch and just posting the resulting code; but that's not going to help you with your homework.

My advice is, rewrite it from scratch instead of fixing it.

It should have a global currently_running_process variable, a global current_time variable, one function to increase the current time, and one function for the scheduler itself.

The function to increase the current time would:

• for each process on the scheduler's linked list, increase the waiting time
• do current_time++
• find any processes that should be started (current_time == arrival_time) and append any started processes to the end of the scheduler's linked list

The scheduler function should:

• remove the first process from the scheduler's linked list
• determine how much time that process should use (the time slice length or the process' remaining time, whichever is lower)
• subtract that amount of time from the process' remaining time
• call the increase_time() function in a loop, until that amount of time has passed
• if the process' remaining time is not zero; put the process back onto the end of the linked list
• if the process` remaining time was zero, check if the scheduler's linked list is empty and exit the program if it is

Note: I'd start with current_time = -1; and call the function to increase the current time once before calling the scheduler function; so that any processes with arrival_time == 0 would be added to the scheduler's linked list before the scheduler starts working (and so that the scheduler function doesn't see an empty list as soon as it's started).