操作系统实验3：文件管理（磁盘调度）

Posted 2022-01-27 拾年之璐

注：本文记录　WHUT-计算机学院-操作系统 课程　实验3：文件管理（磁盘调度）

​纸上得来终觉浅，觉知此事需躬行！

1、实验内容： 

•实验预备：掌握磁盘调度的相关内容，对磁盘结构及调度算法有深入的理解。

•实验内容：模拟实现磁盘调度功能

•具体要求：

• • 
    
• –任选一种计算机高级语言编程实现
• –选择2~3种磁盘调度算法（先来先服务、最短寻道时间优先、电梯算法）模拟实现磁盘调度
• –能够输入当前磁头的位置、磁头移动方向、磁道访问请求序列等
• –能够显示磁盘调度结果（磁头依次访问的磁道号顺序），并计算磁头移动的总磁道数等 
  • 
    

2、运行截图：

3、源代码：

 本次实验难度不大，代码建议参考使用，不建议完全Ctrl+C and Ctrl+V！！！

#include <iostream>
#include <cmath>
#include <stack>
using namespace std;

int trackNum = 8;//访问磁道数：8
struct List 
  int track;//访问磁道
  bool isVisited = false;//磁道状态
;
List list[8];

int path[8];//访问顺序
int totalTrack = 0; //磁头走过的总道数

void initList();//初始化

/*先来先服务*/
void FCFS(int start) 
  /*添加：初始化list  */
  initList();

  totalTrack = 0;//清空
  for (int i = 0; i < trackNum; i++) 
    if (i == 0) 
      totalTrack += abs(list[i].track - start);
    
    else 
      totalTrack += abs(list[i].track - list[i-1].track);
    
    list[i].isVisited = true;//修改状态为已被访问
    path[i] = i;//访问节点顺序
  

  //输出顺序
  cout << "走道顺序：" << start << " → ";
  for (int i = 0; i < trackNum-1; i++) 
    cout<<list[path[i]].track<< " → ";
  
  cout << list[path[trackNum-1]].track << endl;

  //输出移动总磁道数
  cout << "磁头移动总磁道数：" << totalTrack << endl;
  cout << endl;


/*最短寻道优先*/
int closest(int now);
void SSTF(int start) 
  /*添加：初始化list 的节点访问状态 */
  initList();

  totalTrack = 0;//清空
  for (int i = 0; i < trackNum; i++) 
    if (i == 0) 
      totalTrack += abs(list[closest(start)].track - start);
      path[i] = closest(start);
    
    else 
      totalTrack += abs(list[closest(list[path[i - 1]].track)].track - list[path[i - 1]].track);
      path[i] = closest(list[path[i - 1]].track);
    
    list[path[i]].isVisited = true;//修改状态为已被访问
  

  //输出顺序
  cout << "走道顺序：" << start << " → ";
  for (int i = 0; i < trackNum - 1; i++) 
    cout << list[path[i]].track << " → ";
  
  cout << list[path[trackNum-1]].track << endl;

  //输出移动总磁道数
  cout << "磁头移动总磁道数：" << totalTrack << endl << endl;


//寻找距离当前磁道最近的磁道，返回当前磁道的编号
int closest(int now) 
  int min = 0x7FFFFFFF;
  int flag = -1;
  for (int i = 0; i < trackNum; i++) 
    if (list[i].isVisited == false && abs(list[i].track - now) < min) 
      min = abs(list[i].track - now);
      flag = i;
    
  
  return flag;


/*扫描算法（电梯算法）*///direct：方向，左为0，右为其他；
void SCAN(int start,int direct) 
  /*添加：初始化list 的节点访问状态 */
  initList();

  //排序，从小到大
  for (int i = 0; i < trackNum; i++) 
    int flag = -1;
    int  min = 0x7FFFFFFF;

    for (int j = 0; j < trackNum; j++) 
      if (list[j].track < min &&list[j].isVisited == false) 
        min = list[j].track;
        flag = j;
      
    
    path[i] = flag;
    list[flag].isVisited = true;
  

  totalTrack = 0;//清空

  //如果读写头起始位置比最小磁道还小
  if (start<=list[path[0]].track) 
    totalTrack = list[path[trackNum]].track - start;

    cout << "走道顺序：" << start << " → ";
    for (int i = 0; i < trackNum - 1; i++) 
      cout << list[path[i]].track << " → ";
    
    cout << list[path[trackNum-1]].track << endl;
  

  //如果读写头起始位置比最大磁道还大
  else if (start >= list[path[trackNum-1]].track) 
    totalTrack = start - list[path[0]].track;

    cout << "走道顺序：" << start << " → ";
    for (int i = trackNum - 1; i > 0; i--) 
      cout << list[path[i]].track << " → ";
    
    cout << list[path[0]].track << endl;

  
  //如果读写头起始位置 介于最小最大之间
  else   

    stack<int> tempstack;
    cout << "走道顺序：" << start << " → ";
    int flag = 0;
    for (int i = 0; i < trackNum; i++) 
      if (list[path[i]].track <= start) 
        tempstack.push(list[path[i]].track);
        flag = i;
      
    
    //先向左
    if (direct == 0) 
      totalTrack = start - list[path[0]].track + list[path[trackNum - 1]].track - list[path[0]].track;

      while (!tempstack.empty())
        cout << tempstack.top() << " → ";
        tempstack.pop();
      
      for (int i = flag + 1; i < trackNum-1; i++) 
        cout << list[path[i]].track << " → ";
      
      cout << list[path[trackNum-1]].track << endl;
    
    //向右走
    else 
      totalTrack = list[path[trackNum - 1]].track - list[path[0]].track + list[path[trackNum - 1]].track - start;

      for (int i = flag + 1; i < trackNum; i++) 
        cout << list[path[i]].track << " → ";
      
      while (!tempstack.empty()) 
        cout << tempstack.top();
        tempstack.pop();
        if (!tempstack.empty())
          cout<< " → ";
      
      cout << endl;
    
  

  //输出移动总磁道数
  cout << "磁头移动总磁道数：" << totalTrack << endl << endl;


void initList() 
  for (int i = 0; i < trackNum; i++) 
    list[i].isVisited = false;
  


int main() 

  cout << "请输入磁道访问请求序列：";
  for (int i = 0; i < trackNum; i++) 
    cin >> list[i].track;
  
  cout << endl;
  while (1) 
    cout << "　１：先来先服务算法\\n　２：最短寻道时间优先算法\\n　３：电梯算法\\n其他：退出" << endl;
    cout << "请输入您选择的算法：";
    int choose, start, direct;
    cin >> choose;
    if (choose != 1 && choose != 2 && choose != 3)
      break;

    cout << "请输入初始磁头位置：";
    cin >> start;
    switch (choose)
    
    case 1:
      FCFS(start);
      break;

    case 2:
      SSTF(start);
      break;

    case 3:
      cout << "０　：向左移动\\n其他：向右移动\\n请输入磁头移动方向：";
      cin >> direct;
      SCAN(start, direct);
      break;

    default:
      break;