生成一份关于四种常用磁盘调度算法的伪代码
时间: 2024-05-12 19:15:21 浏览: 90
以下是四种常用磁盘调度算法的伪代码:
1. 先来先服务 (FCFS) 算法:
```
algorithm FCFS(diskQueue)
{
currentTrack = 0;
totalMovement = 0;
for (i = 0; i < diskQueue.length; i++) {
track = diskQueue[i];
movement = abs(track - currentTrack);
totalMovement += movement;
currentTrack = track;
}
return totalMovement;
}
```
2. 最短寻道时间优先 (SSTF) 算法:
```
algorithm SSTF(diskQueue)
{
currentTrack = 0;
totalMovement = 0;
while (diskQueue.length > 0) {
nextTrack = findNextTrack(diskQueue, currentTrack);
movement = abs(nextTrack - currentTrack);
totalMovement += movement;
currentTrack = nextTrack;
diskQueue.remove(nextTrack);
}
return totalMovement;
}
function findNextTrack(diskQueue, currentTrack)
{
minDistance = infinity;
nextTrack = null;
for (i = 0; i < diskQueue.length; i++) {
distance = abs(diskQueue[i] - currentTrack);
if (distance < minDistance) {
minDistance = distance;
nextTrack = diskQueue[i];
}
}
return nextTrack;
}
```
3. 扫描 (SCAN) 算法:
```
algorithm SCAN(diskQueue, direction)
{
currentTrack = 0;
totalMovement = 0;
while (diskQueue.length > 0) {
nextTrack = findNextTrack(diskQueue, currentTrack, direction);
if (nextTrack == null) {
direction = reverseDirection(direction);
continue;
}
movement = abs(nextTrack - currentTrack);
totalMovement += movement;
currentTrack = nextTrack;
diskQueue.remove(nextTrack);
}
return totalMovement;
}
function findNextTrack(diskQueue, currentTrack, direction)
{
minDistance = infinity;
nextTrack = null;
for (i = 0; i < diskQueue.length; i++) {
distance = diskQueue[i] - currentTrack;
if (direction == "up" && distance >= 0 && distance < minDistance) {
minDistance = distance;
nextTrack = diskQueue[i];
} else if (direction == "down" && distance <= 0 && abs(distance) < minDistance) {
minDistance = abs(distance);
nextTrack = diskQueue[i];
}
}
return nextTrack;
}
function reverseDirection(direction)
{
if (direction == "up") {
return "down";
} else {
return "up";
}
}
```
4. 循环扫描 (C-SCAN) 算法:
```
algorithm CSCAN(diskQueue, direction)
{
currentTrack = 0;
totalMovement = 0;
while (diskQueue.length > 0) {
nextTrack = findNextTrack(diskQueue, currentTrack, direction);
if (nextTrack == null) {
totalMovement += abs(currentTrack - maxTrack);
currentTrack = 0;
direction = "up";
continue;
}
movement = abs(nextTrack - currentTrack);
totalMovement += movement;
currentTrack = nextTrack;
diskQueue.remove(nextTrack);
}
return totalMovement;
}
function findNextTrack(diskQueue, currentTrack, direction)
{
minDistance = infinity;
nextTrack = null;
for (i = 0; i < diskQueue.length; i++) {
distance = diskQueue[i] - currentTrack;
if (direction == "up" && distance >= 0 && distance < minDistance) {
minDistance = distance;
nextTrack = diskQueue[i];
} else if (direction == "down" && distance <= 0 && abs(distance) < minDistance) {
minDistance = abs(distance);
nextTrack = diskQueue[i];
}
}
return nextTrack;
}
```