experiment2.c

//Write a C program to simulate multi-level queue scheduling algorithm considering the following scenario. All the processes in the system are divided into two categories - system processes and user processes. System processes are to be given higher priority than user processes. Use FCFS scheduling for the processes in each queue.


#include <stdio.h>

struct Process {
    int pid;           
    int arrivalTime;   
    int burstTime;     
    int waitingTime;
    int turnaroundTime;
};

void calculateFCFS(struct Process p[], int n, int startTime) {
    int totalWaiting = 0, totalTurnaround = 0;
    int currentTime = startTime;

    for (int i = 0; i < n; i++) {
        if (currentTime < p[i].arrivalTime)
            currentTime = p[i].arrivalTime;

        p[i].waitingTime = currentTime - p[i].arrivalTime;
        currentTime += p[i].burstTime;
        p[i].turnaroundTime = p[i].waitingTime + p[i].burstTime;

        totalWaiting += p[i].waitingTime;
        totalTurnaround += p[i].turnaroundTime;
    }

    printf("\nPID\tArrival\tBurst\tWaiting\tTurnaround");
    for (int i = 0; i < n; i++) {
        printf("\nP%d\t%d\t%d\t%d\t%d",
               p[i].pid, p[i].arrivalTime, p[i].burstTime,
               p[i].waitingTime, p[i].turnaroundTime);
    }

    printf("\nAverage Waiting Time: %.2f", (float)totalWaiting / n);
    printf("\nAverage Turnaround Time: %.2f\n", (float)totalTurnaround / n);
}

int main() {
    int n1, n2;
    printf("Enter number of System processes: ");
    scanf("%d", &n1);
    struct Process systemP[n1];

    for (int i = 0; i < n1; i++) {
        systemP[i].pid = i + 1;
        printf("\nEnter Arrival Time and Burst Time for System Process P%d: ", i + 1);
        scanf("%d %d", &systemP[i].arrivalTime, &systemP[i].burstTime);
    }

    printf("\nEnter number of User processes: ");
    scanf("%d", &n2);
    struct Process userP[n2];

    for (int i = 0; i < n2; i++) {
        userP[i].pid = i + 1;
        printf("\nEnter Arrival Time and Burst Time for User Process P%d: ", i + 1);
        scanf("%d %d", &userP[i].arrivalTime, &userP[i].burstTime);
    }

    printf("\n===== SYSTEM PROCESSES (HIGH PRIORITY) =====");
    calculateFCFS(systemP, n1, 0);

    
    int totalSystemTime = 0;
    for (int i = 0; i < n1; i++)
        totalSystemTime += systemP[i].burstTime;

    printf("\n===== USER PROCESSES (LOW PRIORITY) =====");
    calculateFCFS(userP, n2, totalSystemTime);

    return 0;
}