磁盘调度算法c语言

磁盘调度算法是用来优化磁盘访问时间，常见的算法有FCFS、SSTF、SCAN、C-SCAN等。下面是一个使用C语言实现SCAN算法的示例代码：

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

#define MAX 1000

int queue[MAX];
int head, tail;

void initQueue() {
    head = tail = 0;
}

int isQueueEmpty() {
    return head == tail;
}

int isQueueFull() {
    return (tail + 1) % MAX == head;
}

void enqueue(int value) {
    if (isQueueFull()) {
        printf("Queue is full\n");
        exit(1);
    }
    queue[tail] = value;
    tail = (tail + 1) % MAX;
}

int dequeue() {
    if (isQueueEmpty()) {
        printf("Queue is empty\n");
        exit(1);
    }
    int value = queue[head];
    head = (head + 1) % MAX;
    return value;
}

void scan(int arr[], int n, int start) {
    int i, pos, move = 0;
    int left = start - 1, right = start + 1;
    while (left >= 0 || right < n) {
        if (left >= 0 && arr[left] >= 0) {
            enqueue(arr[left]);
            arr[left] = -1;
            left--;
        } else if (right < n && arr[right] >= 0) {
            enqueue(arr[right]);
            arr[right] = -1;
            right++;
        } else {
            if (left >= 0) {
                left--;
            }
            if (right < n) {
                right++;
            }
        }
    }
    printf("Sequence of disk access:\n%d", start);
    while (!isQueueEmpty()) {
        pos = dequeue();
        printf(" -> %d", pos);
        move += abs(start - pos);
        start = pos;
    }
    printf("\nTotal head movement: %d\n", move);
}

int main() {
    int n, start, i;
    int arr[MAX];
    printf("Enter the number of disk requests: ");
    scanf("%d", &n);
    printf("Enter the disk requests: ");
    for (i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    printf("Enter the starting position: ");
    scanf("%d", &start);
    initQueue();
    scan(arr, n, start);
    return 0;
}

该代码实现了SCAN算法，使用循环队列来存储待访问的磁道号，遍历磁道号数组，将其存储到队列中，然后按照磁头的移动顺序输出磁道号，并计算磁头的总移动距离。