Question

Write a C/C++ program which reads in a list of process names and integer times from stdin/cin and simulates round-robin CPU scheduling on the list. The input is a list of lines each consisting of a process name and an integer time, e.g. ProcessA 4 ProcessB 10 Read the list until end of transmission (^d). You should read the list and represent it in a linked list data structure. You should use the alarm system call to schedule a timer interrupt every 3 seconds. The interrupt handler should pick the next process from the process list, write a message saying how much time it has left to execute, i.e. ProcessA 4 Then update its time left to execute by subtracting 3 seconds and return it to the end of the queue. If the process had no time left to execute, you should write a message saying this i.e. ProcessA Finished And delete this process from the linked list. If there are no processes left to execute, write a message saying No processes left And terminate your program.

Answer 1

// C++ program for implementation of RR scheduling 
#include<iostream> 
using namespace std; 
  
// Function to find the waiting time for all processes

void findWaitingTime(int processes[], int n, 
             int bt[], int wt[], int quantum) 
{ 
    // Make a copy of burst times bt[] to store remaining burst times
    int rem_bt[n]; 
    for (int i = 0 ; i < n ; i++) 
        rem_bt[i] =  bt[i]; 
  
    int t = 0; // Current time 
  
    // Keep traversing processes in round robin manner until all of them are not done. 
    while (1) 
    { 
        bool done = true; 
        // Traverse all processes one by one repeatedly 
        for (int i = 0 ; i < n; i++) 
        { 
            // If burst time of a process is greater than 0 
            // then only need to process further 
            if (rem_bt[i] > 0) 
            { 
                done = false; // There is a pending process 
  
                if (rem_bt[i] > quantum) 
                { 
                    // Increase the value of t i.e. shows 
                    // how much time a process has been processed 
                    t += quantum; 
  
                    // Decrease the burst_time of current process 
                    // by quantum 
                    rem_bt[i] -= quantum; 
                } 
  
                // If burst time is smaller than or equal to 
                // quantum. Last cycle for this process 
                else
                { 
                    // Increase the value of t i.e. shows 
                    // how much time a process has been processed 
                    t = t + rem_bt[i]; 
  
                    // Waiting time is current time minus time 
                    // used by this process 
                    wt[i] = t - bt[i]; 
  
                    // As the process gets fully executed 
                    // make its remaining burst time = 0 
                    rem_bt[i] = 0; 
                } 
            } 
        } 
  
        // If all processes are done 
        if (done == true) 
          break; 
    } 
} 
  
// Function to calculate turn around time 
void findTurnAroundTime(int processes[], int n, 
                        int bt[], int wt[], int tat[]) 
{ 
    // calculating turnaround time by adding 
    // bt[i] + wt[i] 
    for (int i = 0; i < n ; i++) 
        tat[i] = bt[i] + wt[i]; 
} 
  
// Function to calculate average time 
void findavgTime(int processes[], int n, int bt[], 
                                     int quantum) 
{ 
    int wt[n], tat[n], total_wt = 0, total_tat = 0; 
  
    // Function to find waiting time of all processes 
    findWaitingTime(processes, n, bt, wt, quantum); 
  
    // Function to find turn around time for all processes 
    findTurnAroundTime(processes, n, bt, wt, tat); 
  
    // Display processes along with all details 
    cout << "Processes "<< " Burst time "
         << " Waiting time " << " Turn around time\n"; 
  
    // Calculate total waiting time and total turn 
    // around time 
    for (int i=0; i<n; i++) 
    { 
        total_wt = total_wt + wt[i]; 
        total_tat = total_tat + tat[i]; 
        cout << " " << i+1 << "\t\t" << bt[i] <<"\t "
             << wt[i] <<"\t\t " << tat[i] <<endl; 
    } 
  
    cout << "Average waiting time = "
         << (float)total_wt / (float)n; 
    cout << "\nAverage turn around time = "
         << (float)total_tat / (float)n; 
}  
int main() 
{ 
    // process id's 
    int processes[] = { 1, 2, 3}; 
    int n = sizeof processes / sizeof processes[0]; 
  
    // Burst time of all processes 
    int burst_time[] = {10, 5, 8}; 
  
    // Time quantum 
    int quantum = 2; 
    findavgTime(processes, n, burst_time, quantum); 
    return 0; 
}