Priority scheduling

 

// Priority scheduling 

#include <stdio.h>

struct Process { int pid, arrival, burst, priority, completion, turnaround, waiting, response;};

void sortProcesses (struct Process p[], int n) {

for (int i = 0; i<n-1; i++) {

for (int j=0; j < n - i – 1;j++) {

if (p[j].arrival > p[j + 1] .arrival ||

(p[j].arrival == p[j + 1] .arrival && p[j].priority > p[j+1].priority))

struct Process temp = p[j];

p[j] = p[j + 1];p[j+1]= temp;   }}}}

void calculateTimes(struct Process p[], int n) {

int currentTime = 0, completed = 0, visited[n];

for (int i=0; i < n; i++) visited[i] = 0;

while (completed < n) {

int idx = -1, minPriority=1e9;

for (int = 0; i < n; i++) {

if (!visited[i] && p[1].arrival <= currentTime && p[i].priority < minPriority){ 

idx = i;            minPriority = p[i].priority;   }}

if (idx != -1) {   visited[idx] = 1;

if (currentTime < p[idx].arrival) currentTime = p[idx].arrival;

p[idx].response = currentTime - p[idx].arrival;

p[idx].completion = currentTime + p[idx].burst;

p[idx].turnaround = p[idx].completion - p[idx].arrival;

p[idx].waiting = p[idx].turnaround - p[idx].burst;

currentTime += p[idx].burst;

completed++;   } else {

currentTime++;   }}}

void printTable ( struct Process p[], int n) {

float totalTAT = 0, totalWT=0, totalRT = 0;

printf("\nPID\tArrival\tBurst\tPriority\tCompletion\tTAT\tWT\tRT\n");

for (int i = 0; i < n; i++) {

totalTAT += p[i].turnaround;

totalWT += p[i].waiting;

totalRT += p[i].response;

printf("%d\t%d\t%d\t%d\t\t%d\t\t%d\t%d\t%d\n",

p[i].pid, p[i].arrival, p[i].burst, p[i].priority, p[i].completion, p[i].turnaround, p[i].waiting, p[i].response);  }

printf("\nAverage Turnaround Time: %.2f", totalTAT / n);

printf("\nAverage Waiting Time: %.2f", totalWT / n);

printf("\nAverage Response Time: %.2f\n", totalRT / n);   }

int main() {   int n;

printf("Enter number of processes: ");   scanf("%d", &n);

struct Process p[n];

for (int i = 0; i < n; i++) {

p[i].pid=i+1;

printf("\nProcess %d Arrival Time: ", i + 1);  scanf("%d", &p[i].arrival);

printf("Process %d Burst Time: ", i + 1);          scanf("%d", &p[i].burst);

printf("Process %d Priority (lower is higher): ", i + 1);  scanf("%d", &p[i].priority);  }

sortProcesses(p, n);

calculateTimes (p, n);

printTable(p, n);         return 0;  }