: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:

【操作系统】实验3:文件管理(磁盘调度)_OS

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;
}
}
}