MIT-Curricular/OS/C/Week6/menudriven.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

# define MAX 4

	typedef struct {
		char pid[5]; // Process ID (string)
		int at; // Arrival Time
		int bt; // Burst Time
		int priority; // Priority (lower value = higher priority)
		int ct; // Completion Time
		int tat; // Turnaround Time
		int wt; // Waiting Time
		int rt; // Response Time
		int remaining_bt; // Remaining Burst Time (for preemptive sjf)
		int is_completed; // completion flag
	} Process;

	void swap(Process *a, Process *b) {
		Process temp = *a;
		*a = *b;
		*b = temp;
	}

	// Function to calculate Completion Time, Turnaround Time, and Waiting Time
	void calculate_times(Process processes[], int n) {
		for (int i = 0; i < n; i++) {
		processes[i].tat = processes[i].ct - processes[i].at;
		processes[i].wt = processes[i].tat - processes[i].bt;
		}
	}

	// Function to calculate average times
	void calculate_averages(Process processes[], int n, float *avg_ct,
		float *avg_tat, float *avg_wt, float *avg_rt) {
		*avg_ct = 0;
		*avg_tat = 0;
		*avg_wt = 0;
		*avg_rt = 0;

		for (int i = 0; i < n; i++) {
		*avg_ct += processes[i].ct;
		*avg_tat += processes[i].tat;
		*avg_wt += processes[i].wt;
		*avg_rt += processes[i].rt;
		}

		*avg_ct /= n;
		*avg_tat /= n;
		*avg_wt /= n;
		*avg_rt /= n;
	}

	// Function to display the Gantt chart
	void display_gantt_chart(Process processes[], int n, int timeline[], int timeline_index) {
		printf("\nGantt Chart:\n");
		printf("-----------------------------------------------------------\n");
		int last_process = -1;
		for(int i = 0; i < timeline_index; i++) {
			if(timeline[i] != last_process) {
				printf("%s ", processes[timeline[i]].pid);
				last_process = timeline[i];
			}
		}
		printf("\n-----------------------------------------------------------\n");
	}

	// Function to display the process table
	void display_table(Process processes[], int n) {
		printf("--------------------------------------------------------------------"
		"------\n");
		printf("| PID   | AT  | BT  | CT  | TAT | WT  | RT  |\n");
		printf("--------------------------------------------------------------------"
		"------\n");
		for (int i = 0; i < n; i++) {
		printf("| %-5s | %-3d | %-3d | %-3d | %-3d | %-3d | %-3d |\n",
		processes[i].pid, processes[i].at, processes[i].bt,
		processes[i].ct, processes[i].tat, processes[i].wt,
		processes[i].rt);
		}
		printf("--------------------------------------------------------------------"
		"------\n");
	}

	// Preemptive SJF
	void preemptive_sjf(Process processes[], int n){

	// process sort by AT
	for (int i = 0; i < n -1; i++){
		for(int j = 0; j < n - i - 1; j++){
			if(processes[j].at > processes[j+1].at){
				swap(&processes[j], &processes[j + 1]);
			}
		}
	}

	//remaining BT + completion flag
	for (int i = 0; i < n; i++){
		processes[i].remaining_bt = processes[i].bt;
		processes[i].rt = -1;
		processes[i].is_completed = 0;
	}

	// init for values of relevant variables, shortest=-1 to indicate no process is selected
	int current_time = 0;
	int completed = 0;
	int shortest = -1;

	int *timeline = (int *)malloc((n*100)*sizeof(int));
	if (timeline == NULL) {
		perror ("MemAlloc Error");
		return;
	}

	int timeline_index = 0;
	int last_process = -1;

	// setting to large values to prevent issues
	while (completed != n)
	{
		shortest = -1;
		int min_bt = 9999;

		for (int j = 0; j < n; j++) {
			if (processes[j].at <= current_time && processes[j].remaining_bt > 0 && processes[j].remaining_bt < min_bt){
				min_bt = processes[j].remaining_bt;
				shortest = j;
			}
		}

		if (shortest == -1){
			current_time++;
			continue;
		}

		if(processes[shortest].rt == -1) {
			processes[shortest].rt = current_time - processes[shortest].at;
		}

		if(shortest != last_process) {
			timeline[timeline_index++] = shortest;
			last_process = shortest;
		}

		processes[shortest].remaining_bt--;
		current_time++;

		if (processes[shortest].remaining_bt == 0) {
			completed++;
			processes[shortest].ct = current_time;
			processes[shortest].is_completed = 1;
		}
	}

	calculate_times(processes, n);

	float avg_ct, avg_tat, avg_wt, avg_rt;
	calculate_averages(processes, n, &avg_ct, &avg_tat, &avg_wt, &avg_rt);


	printf("\nPreemptive SJF Scheduling:\n");
	display_table(processes, n);


	printf("\nAverage Completion Time: %.2f\n", avg_ct);
	printf("Average Turnaround Time: %.2f\n", avg_tat);
	printf("Average Waiting Time: %.2f\n", avg_wt);
	printf("Average Response Time: %.2f\n", avg_rt);


	display_gantt_chart(processes, n, timeline, timeline_index);
	free(timeline);
}

	void round_robin(Process processes[], int n, int quantum) {

			for (int i = 0; i < n; i++) {
				processes[i].remaining_bt = processes[i].bt;
				processes[i].rt = -1;
				processes[i].is_completed = 0;
			}


	int current_time = 0;
			int completed = 0;
			int i = 0;
			int *timeline = (int *)malloc((n * 100) * sizeof(int));

	if (timeline == NULL) {
				perror("Failed to allocate memory for timeline");
				return;
				}

	int timeline_index = 0;
	int last_process = -1;

			while (completed != n) {
				if (processes[i].remaining_bt > 0 && processes[i].at <= current_time) {
					if (processes[i].rt == -1) {
						processes[i].rt = current_time - processes[i].at;
					}

					if(i != last_process) {
						timeline[timeline_index++] = i;
						last_process = i;
					}

					int execute_time = (processes[i].remaining_bt > quantum) ? quantum : processes[i].remaining_bt;
					processes[i].remaining_bt -= execute_time;
					current_time += execute_time;

					if (processes[i].remaining_bt == 0) {
						completed++;
						processes[i].ct = current_time;
						processes[i].is_completed = 1;
					}

				} else if (processes[i].at > current_time) {
					current_time++;
				}

				i = (i + 1) % n;
				if (current_time > 1000) break;
			}

			calculate_times(processes, n);

			float avg_ct, avg_tat, avg_wt, avg_rt;
			calculate_averages(processes, n, &avg_ct, &avg_tat, &avg_wt, &avg_rt);

			printf("\nRound Robin Scheduling (Quantum = %d):\n", quantum);
			display_table(processes, n);

			printf("\nAverage Completion Time: %.2f\n", avg_ct);
			printf("Average Turnaround Time: %.2f\n", avg_tat);
			printf("Average Waiting Time: %.2f\n", avg_wt);
			printf("Average Response Time: %.2f\n", avg_rt);

			display_gantt_chart(processes, n, timeline, timeline_index);
			free(timeline);
	}

	void non_preemptive_priority(Process processes[], int n) {
			for (int i = 0; i < n - 1; i++) {
				for (int j = 0; j < n - i - 1; j++) {
					if (processes[j].at > processes[j + 1].at) {
						swap(&processes[j], &processes[j + 1]);
					}
				}
			}

			int current_time = 0;
			int completed = 0;
			int *timeline = (int *)malloc((n * 100) * sizeof(int));

	if (timeline == NULL) {
				perror("Failed to allocate memory for timeline");
				return;
			}

	int timeline_index = 0;
	int last_process = -1;

			while (completed != n) {
				int highest_priority = -1;
				int min_priority = 9999;

				for (int j = 0; j < n; j++) {
					if (processes[j].at <= current_time && processes[j].bt > 0 && processes[j].priority < min_priority) {
						min_priority = processes[j].priority;
						highest_priority = j;
					}
				}

				if (highest_priority == -1) {
					current_time++;
					continue;
				}

				if (processes[highest_priority].rt == -1) {
					processes[highest_priority].rt = current_time - processes[highest_priority].at;
				}

				if(highest_priority != last_process) {
					timeline[timeline_index++] = highest_priority;
					last_process = highest_priority;
				}

				current_time += processes[highest_priority].bt;
				processes[highest_priority].ct = current_time;
				processes[highest_priority].bt = 0;
				completed++;
		}

			calculate_times(processes, n);

			float avg_ct, avg_tat, avg_wt, avg_rt;
			calculate_averages(processes, n, &avg_ct, &avg_tat, &avg_wt, &avg_rt);

			printf("\nNon-Preemptive Priority Scheduling:\n");
			display_table(processes, n);

			printf("\nAverage Completion Time: %.2f\n", avg_ct);
			printf("Average Turnaround Time: %.2f\n", avg_tat);
			printf("Average Waiting Time: %.2f\n", avg_wt);
			printf("Average Response Time: %.2f\n", avg_rt);

			display_gantt_chart(processes, n, timeline, timeline_index);
			free(timeline);
	}

	int main() {
			int n, choice, quantum;

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

			Process processes[n];

		// Input process details
		for (int i = 0; i < n; i++) {
	printf("\nEnter details for process %d:\n", i + 1);

	printf("PID: ");
	scanf("%s", processes[i].pid);

	printf("Arrival Time: ");
			scanf("%d", &processes[i].at);

	printf("Burst Time: ");
			scanf("%d", &processes[i].bt);

	printf("Priority (lower value = higher priority): ");
			scanf("%d", &processes[i].priority);

	processes[i].rt = 0; // Initialize response time
			processes[i].is_completed = 0; // Initialize completion flag
		}

		// Display initial table
			printf("\nInitial Process Table:\n");
			printf("-----------------------\n");
			printf("| PID   | AT  | BT  |\n");
			printf("-----------------------\n");

			for (int i = 0; i < n; i++) {
				printf("| %-5s | %-3d | %-3d |\n", processes[i].pid, processes[i].at, processes[i].bt);
			}

	printf("-----------------------\n");

		// Algorithm Selection Menu with Loop and Exit
			while (1) {
				printf("\nChoose a scheduling algorithm:\n");
				printf("1. Preemptive SJF\n");
				printf("2. Round Robin\n");
				printf("3. Non-Preemptive Priority\n");
				printf("4. Exit\n");
				printf("Enter your choice: ");

		scanf("%d", &choice);

		switch (choice) {
				case 1:
					preemptive_sjf(processes, n);
					break;
				case 2:
					printf("Enter the time quantum: ");
					scanf("%d", &quantum);
					round_robin(processes, n, quantum);
							break;
						case 3:
					non_preemptive_priority(processes, n);
					break;
						case 4:
					printf("Exiting program.\n");
					exit(0);
						default:
					printf("Invalid choice. Please try again.\n");
				}
		}

		return 0;
	}