用c语言编写 对磁盘进行移臂操作，分别模拟FCFS、SSTF、SCAN、CSCAN四种磁盘调度算法计算移动的总磁道数和平均寻道长度。

这是一道涉及操作系统和磁盘调度算法的题目，需要使用C语言来进行编写。以下是简单的实现思路：

1. 定义一个数组来表示磁道队列，每个元素表示一个磁道。
2. 随机生成一个起始磁道和一定数量的请求磁道，存储到磁道队列中。
3. 实现FCFS算法：按照请求的顺序进行移动，计算总磁道数和平均寻道长度。
4. 实现SSTF算法：选择最近的请求进行移动，计算总磁道数和平均寻道长度。
5. 实现SCAN算法：按照请求的方向进行移动，当到达磁道队列的边界时改变方向，计算总磁道数和平均寻道长度。
6. 实现CSCAN算法：类似于SCAN算法，但在边界处不改变方向，而是回到队列的另一端，计算总磁道数和平均寻道长度。
7. 输出每种算法的结果。

下面是代码示例：

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

#define MAX_TRACK 200   // 磁道总数
#define MAX_REQUEST 20  // 请求磁道数
#define START_TRACK 50  // 起始磁道号

// 定义磁道队列
int track_queue[MAX_REQUEST];

// 随机生成请求磁道
void generate_requests() {
    int i;
    for (i = 0; i < MAX_REQUEST; i++) {
        track_queue[i] = rand() % MAX_TRACK;
    }
}

// FCFS算法
void fcfs() {
    int i, total_tracks = 0, current_track = START_TRACK;
    float avg_seek_length;

    for (i = 0; i < MAX_REQUEST; i++) {
        total_tracks += abs(current_track - track_queue[i]);
        current_track = track_queue[i];
    }

    avg_seek_length = (float)total_tracks / (float)MAX_REQUEST;

    printf("\nFCFS algorithm:\n");
    printf("Total tracks: %d\n", total_tracks);
    printf("Average seek length: %f\n", avg_seek_length);
}

// SSTF算法
void sstf() {
    int i, total_tracks = 0, current_track = START_TRACK, min_distance, min_index, j;

    for (i = 0; i < MAX_REQUEST; i++) {
        min_distance = MAX_TRACK;
        for (j = 0; j < MAX_REQUEST; j++) {
            if (abs(current_track - track_queue[j]) < min_distance) {
                min_distance = abs(current_track - track_queue[j]);
                min_index = j;
            }
        }
        total_tracks += min_distance;
        current_track = track_queue[min_index];
        track_queue[min_index] = MAX_TRACK + 1; // 标记已访问
    }

    float avg_seek_length = (float)total_tracks / (float)MAX_REQUEST;

    printf("\nSSTF algorithm:\n");
    printf("Total tracks: %d\n", total_tracks);
    printf("Average seek length: %f\n", avg_seek_length);
}

// SCAN算法
void scan() {
    int i, total_tracks = 0, current_track = START_TRACK, direction = 1;

    // 排序请求队列
    for (i = 0; i < MAX_REQUEST - 1; i++) {
        int j;
        for (j = i + 1; j < MAX_REQUEST; j++) {
            if (track_queue[i] > track_queue[j]) {
                int temp = track_queue[i];
                track_queue[i] = track_queue[j];
                track_queue[j] = temp;
            }
        }
    }

    for (i = 0; i < MAX_REQUEST; i++) {
        if (current_track < track_queue[i] && direction == 1) {
            total_tracks += track_queue[i] - current_track;
            current_track = track_queue[i];
        }
        else if (current_track > track_queue[i] && direction == -1) {
            total_tracks += current_track - track_queue[i];
            current_track = track_queue[i];
        }
    }

    total_tracks += abs(current_track - (direction == 1 ? MAX_TRACK : 0));

    float avg_seek_length = (float)total_tracks / (float)MAX_REQUEST;

    printf("\nSCAN algorithm:\n");
    printf("Total tracks: %d\n", total_tracks);
    printf("Average seek length: %f\n", avg_seek_length);
}

// CSCAN算法
void cscan() {
    int i, total_tracks = 0, current_track = START_TRACK;

    // 排序请求队列
    for (i = 0; i < MAX_REQUEST - 1; i++) {
        int j;
        for (j = i + 1; j < MAX_REQUEST; j++) {
            if (track_queue[i] > track_queue[j]) {
                int temp = track_queue[i];
                track_queue[i] = track_queue[j];
                track_queue[j] = temp;
            }
        }
    }

    for (i = 0; i < MAX_REQUEST; i++) {
        if (current_track < track_queue[i]) {
            total_tracks += track_queue[i] - current_track;
            current_track = track_queue[i];
        }
    }

    total_tracks += MAX_TRACK - current_track;
    total_tracks += track_queue[0];

    float avg_seek_length = (float)total_tracks / (float)MAX_REQUEST;

    printf("\nCSCAN algorithm:\n");
    printf("Total tracks: %d\n", total_tracks);
    printf("Average seek length: %f\n", avg_seek_length);
}

int main() {
    srand(time(NULL));
    generate_requests();
    fcfs();
    sstf();
    scan();
    cscan();
    return 0;
}