根据以下要求，写出三个相对应的可运行的c语言程序。实验三 简单文件系统设计 一、 实验目的 （1）加深对进程概念的理解，明确进程和程序的区别 （2）深入理解系统如何组织进程 （3）理解常用进程调度算法的具体实现 二、 实验内容 编写C程序模拟实现单处理机系统中的进程调度算法，实现对多个进程的调度模拟，要求采用常见进程调度算法（如先来先服务、时间片轮转和优先级调度等算法）进行模拟调度。

程序一：先来先服务调度算法

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

#define MAX_PROCESS 10

struct Process {
    int pid; // 进程id
    int arrival_time; // 到达时间
    int burst_time; // 执行时间
    int waiting_time; // 等待时间
    int turnaround_time; // 周转时间
};

void FCFS(struct Process processes[], int n) {
    int time = 0;
    float avg_waiting_time = 0, avg_turnaround_time = 0;
    printf("\nFCFS Scheduling:\n");
    for(int i = 0; i < n; i++) {
        printf("\nProcess %d:\n", processes[i].pid);
        printf("Arrival Time: %d\n", processes[i].arrival_time);
        printf("Burst Time: %d\n", processes[i].burst_time);
        if(time < processes[i].arrival_time) {
            time = processes[i].arrival_time;
        }
        processes[i].waiting_time = time - processes[i].arrival_time;
        processes[i].turnaround_time = processes[i].waiting_time + processes[i].burst_time;
        time += processes[i].burst_time;
        printf("Waiting Time: %d\n", processes[i].waiting_time);
        printf("Turnaround Time: %d\n", processes[i].turnaround_time);
        avg_waiting_time += processes[i].waiting_time;
        avg_turnaround_time += processes[i].turnaround_time;
    }
    avg_waiting_time /= n;
    avg_turnaround_time /= n;
    printf("\nAverage Waiting Time: %f\n", avg_waiting_time);
    printf("Average Turnaround Time: %f\n", avg_turnaround_time);
}

int main() {
    struct Process processes[MAX_PROCESS];
    int n;
    printf("Enter number of processes (max %d): ", MAX_PROCESS);
    scanf("%d", &n);
    printf("\nEnter process details:\n");
    for(int i = 0; i < n; i++) {
        printf("\nProcess %d:\n", i+1);
        processes[i].pid = i+1;
        printf("Arrival Time: ");
        scanf("%d", &processes[i].arrival_time);
        printf("Burst Time: ");
        scanf("%d", &processes[i].burst_time);
    }
    FCFS(processes, n);
    return 0;
}

程序二：时间片轮转调度算法

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

#define MAX_PROCESS 10
#define TIME_QUANTUM 2

struct Process {
    int pid; // 进程id
    int arrival_time; // 到达时间
    int burst_time; // 执行时间
    int remaining_burst_time; // 剩余执行时间
    int waiting_time; // 等待时间
    int turnaround_time; // 周转时间
};

void RR(struct Process processes[], int n) {
    int time = 0, completed_processes = 0, i = 0;
    float avg_waiting_time = 0, avg_turnaround_time = 0;
    printf("\nRound Robin Scheduling:\n");
    while(completed_processes < n) {
        if(processes[i].remaining_burst_time > 0) {
            if(processes[i].remaining_burst_time > TIME_QUANTUM) {
                time += TIME_QUANTUM;
                processes[i].remaining_burst_time -= TIME_QUANTUM;
            }
            else {
                time += processes[i].remaining_burst_time;
                processes[i].waiting_time = time - processes[i].arrival_time - processes[i].burst_time;
                processes[i].turnaround_time = time - processes[i].arrival_time;
                completed_processes++;
                processes[i].remaining_burst_time = 0;
                printf("\nProcess %d:\n", processes[i].pid);
                printf("Waiting Time: %d\n", processes[i].waiting_time);
                printf("Turnaround Time: %d\n", processes[i].turnaround_time);
                avg_waiting_time += processes[i].waiting_time;
                avg_turnaround_time += processes[i].turnaround_time;
            }
        }
        i = (i+1) % n;
    }
    avg_waiting_time /= n;
    avg_turnaround_time /= n;
    printf("\nAverage Waiting Time: %f\n", avg_waiting_time);
    printf("Average Turnaround Time: %f\n", avg_turnaround_time);
}

int main() {
    struct Process processes[MAX_PROCESS];
    int n;
    printf("Enter number of processes (max %d): ", MAX_PROCESS);
    scanf("%d", &n);
    printf("\nEnter process details:\n");
    for(int i = 0; i < n; i++) {
        printf("\nProcess %d:\n", i+1);
        processes[i].pid = i+1;
        printf("Arrival Time: ");
        scanf("%d", &processes[i].arrival_time);
        printf("Burst Time: ");
        scanf("%d", &processes[i].burst_time);
        processes[i].remaining_burst_time = processes[i].burst_time;
    }
    RR(processes, n);
    return 0;
}

程序三：优先级调度算法

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

#define MAX_PROCESS 10

struct Process {
    int pid; // 进程id
    int arrival_time; // 到达时间
    int burst_time; // 执行时间
    int priority; // 优先级
    int waiting_time; // 等待时间
    int turnaround_time; // 周转时间
};

void PS(struct Process processes[], int n) {
    int time = 0, completed_processes = 0, i = 0;
    float avg_waiting_time = 0, avg_turnaround_time = 0;
    printf("\nPriority Scheduling:\n");
    while(completed_processes < n) {
        int min_priority = INT_MAX, min_priority_idx = -1;
        for(int j = 0; j < n; j++) {
            if(processes[j].arrival_time <= time && processes[j].priority < min_priority && processes[j].burst_time > 0) {
                min_priority = processes[j].priority;
                min_priority_idx = j;
            }
        }
        if(min_priority_idx == -1) {
            time++;
            continue;
        }
        processes[min_priority_idx].burst_time--;
        if(processes[min_priority_idx].burst_time == 0) {
            completed_processes++;
            processes[min_priority_idx].waiting_time = time - processes[min_priority_idx].arrival_time - processes[min_priority_idx].burst_time;
            processes[min_priority_idx].turnaround_time = time - processes[min_priority_idx].arrival_time;
            printf("\nProcess %d:\n", processes[min_priority_idx].pid);
            printf("Waiting Time: %d\n", processes[min_priority_idx].waiting_time);
            printf("Turnaround Time: %d\n", processes[min_priority_idx].turnaround_time);
            avg_waiting_time += processes[min_priority_idx].waiting_time;
            avg_turnaround_time += processes[min_priority_idx].turnaround_time;
        }
        time++;
    }
    avg_waiting_time /= n;
    avg_turnaround_time /= n;
    printf("\nAverage Waiting Time: %f\n", avg_waiting_time);
    printf("Average Turnaround Time: %f\n", avg_turnaround_time);
}

int main() {
    struct Process processes[MAX_PROCESS];
    int n;
    printf("Enter number of processes (max %d): ", MAX_PROCESS);
    scanf("%d", &n);
    printf("\nEnter process details:\n");
    for(int i = 0; i < n; i++) {
        printf("\nProcess %d:\n", i+1);
        processes[i].pid = i+1;
        printf("Arrival Time: ");
        scanf("%d", &processes[i].arrival_time);
        printf("Burst Time: ");
        scanf("%d", &processes[i].burst_time);
        printf("Priority (higher value means higher priority): ");
        scanf("%d", &processes[i].priority);
    }
    PS(processes, n);
    return 0;
}