java实现四种进程调度算法：先来先服务、时间片轮转调、优先级调度以及短作业优先调度算法

1. 先来先服务调度（FCFS）：按照进程到达的先后顺序分配 CPU 时间片，即先到达的进程先执行。这种调度算法实现简单，但无法适应各种不同类型进程的需要，容易导致长作业等待时间过长。

2. 时间片轮转调度（RR）：每个进程被分配一个时间片，当时间片用完后，CPU 会分配给下一个进程。如果一个进程在时间片结束之前完成，那么 CPU 会立即将时间片分配给下一个进程。这种调度算法可以有效避免长作业等待时间过长的问题，但是需要合理设置时间片长度。

3. 优先级调度算法：每个进程被分配一个优先级，CPU 会优先执行优先级较高的进程。这种调度算法可以保证优先级较高的进程尽快得到执行，但是如果所有进程的优先级都相同，就会导致饥饿问题。

4. 短作业优先调度算法（SJF）：根据进程需要的 CPU 时间长度来进行调度，优先执行需要时间较短的进程。这种调度算法可以有效降低平均等待时间，但是需要准确预测每个进程需要的 CPU 时间长度，否则容易导致长作业等待时间过长。

相关问题

一个c语言代码实现先来先服务调度算法、短作业优先算法、时间片轮转和优先级调度算法

先来先服务调度算法（FCFS）：

#include <stdio.h>
#define MAX 10

struct Process {
    int pid;
    int arrival_time;
    int burst_time;
    int waiting_time;
    int turnaround_time;
};

int main() {
    struct Process p[MAX];
    int n, i;
    float avg_waiting_time = 0, avg_turnaround_time = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);
    for(i=0; i<n; i++) {
        printf("Enter arrival time and burst time for Process %d: ", i+1);
        scanf("%d %d", &p[i].arrival_time, &p[i].burst_time);
        p[i].pid = i+1;
    }

    // calculate waiting time and turnaround time
    p[0].waiting_time = 0;
    for(i=1; i<n; i++) {
        p[i].waiting_time = p[i-1].waiting_time + p[i-1].burst_time;
    }
    for(i=0; i<n; i++) {
        p[i].turnaround_time = p[i].waiting_time + p[i].burst_time;
        avg_waiting_time += p[i].waiting_time;
        avg_turnaround_time += p[i].turnaround_time;
    }

    // print result
    printf("\nProcess\tArrival Time\tBurst Time\tWaiting Time\tTurnaround Time\n");
    for(i=0; i<n; i++) {
        printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].waiting_time, p[i].turnaround_time);
    }
    avg_waiting_time /= n;
    avg_turnaround_time /= n;
    printf("Average Waiting Time: %f\n", avg_waiting_time);
    printf("Average Turnaround Time: %f\n", avg_turnaround_time);

    return 0;
}

短作业优先算法（SJF）：

#include <stdio.h>
#define MAX 10

struct Process {
    int pid;
    int arrival_time;
    int burst_time;
    int waiting_time;
    int turnaround_time;
    int is_completed;
};

int main() {
    struct Process p[MAX];
    int n, i, j;
    float avg_waiting_time = 0, avg_turnaround_time = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);
    for(i=0; i<n; i++) {
        printf("Enter arrival time and burst time for Process %d: ", i+1);
        scanf("%d %d", &p[i].arrival_time, &p[i].burst_time);
        p[i].pid = i+1;
        p[i].is_completed = 0;
    }

    int time = 0, completed = 0;
    while(completed != n) {
        int shortest = -1;
        for(i=0; i<n; i++) {
            if(!p[i].is_completed && p[i].arrival_time <= time) {
                if(shortest == -1 || p[i].burst_time < p[shortest].burst_time) {
                    shortest = i;
                }
            }
        }
        if(shortest != -1) {
            p[shortest].waiting_time = time - p[shortest].arrival_time;
            p[shortest].turnaround_time = p[shortest].waiting_time + p[shortest].burst_time;
            avg_waiting_time += p[shortest].waiting_time;
            avg_turnaround_time += p[shortest].turnaround_time;
            p[shortest].is_completed = 1;
            completed++;
            time += p[shortest].burst_time;
        } else {
            time++;
        }
    }

    // print result
    printf("\nProcess\tArrival Time\tBurst Time\tWaiting Time\tTurnaround Time\n");
    for(i=0; i<n; i++) {
        printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].waiting_time, p[i].turnaround_time);
    }
    avg_waiting_time /= n;
    avg_turnaround_time /= n;
    printf("Average Waiting Time: %f\n", avg_waiting_time);
    printf("Average Turnaround Time: %f\n", avg_turnaround_time);

    return 0;
}

时间片轮转算法（RR）：

#include <stdio.h>
#define MAX 10

struct Process {
    int pid;
    int arrival_time;
    int burst_time;
    int remaining_time;
    int waiting_time;
    int turnaround_time;
    int is_completed;
};

int main() {
    struct Process p[MAX];
    int n, i, j, time_quantum;
    float avg_waiting_time = 0, avg_turnaround_time = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);
    for(i=0; i<n; i++) {
        printf("Enter arrival time and burst time for Process %d: ", i+1);
        scanf("%d %d", &p[i].arrival_time, &p[i].burst_time);
        p[i].pid = i+1;
        p[i].remaining_time = p[i].burst_time;
        p[i].is_completed = 0;
    }

    printf("Enter time quantum: ");
    scanf("%d", &time_quantum);

    int time = 0, completed = 0;
    while(completed != n) {
        for(i=0; i<n; i++) {
            if(!p[i].is_completed && p[i].arrival_time <= time) {
                int execute_time = time_quantum;
                if(p[i].remaining_time < execute_time) {
                    execute_time = p[i].remaining_time;
                }
                p[i].remaining_time -= execute_time;
                time += execute_time;
                if(p[i].remaining_time == 0) {
                    p[i].waiting_time = time - p[i].arrival_time - p[i].burst_time;
                    if(p[i].waiting_time < 0) {
                        p[i].waiting_time = 0;
                    }
                    p[i].turnaround_time = p[i].waiting_time + p[i].burst_time;
                    avg_waiting_time += p[i].waiting_time;
                    avg_turnaround_time += p[i].turnaround_time;
                    p[i].is_completed = 1;
                    completed++;
                }
            }
        }
    }

    // print result
    printf("\nProcess\tArrival Time\tBurst Time\tWaiting Time\tTurnaround Time\n");
    for(i=0; i<n; i++) {
        printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].waiting_time, p[i].turnaround_time);
    }
    avg_waiting_time /= n;
    avg_turnaround_time /= n;
    printf("Average Waiting Time: %f\n", avg_waiting_time);
    printf("Average Turnaround Time: %f\n", avg_turnaround_time);

    return 0;
}

优先级调度算法：

#include <stdio.h>
#define MAX 10

struct Process {
    int pid;
    int arrival_time;
    int burst_time;
    int priority;
    int waiting_time;
    int turnaround_time;
    int is_completed;
};

int main() {
    struct Process p[MAX];
    int n, i, j;
    float avg_waiting_time = 0, avg_turnaround_time = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);
    for(i=0; i<n; i++) {
        printf("Enter arrival time, burst time and priority for Process %d: ", i+1);
        scanf("%d %d %d", &p[i].arrival_time, &p[i].burst_time, &p[i].priority);
        p[i].pid = i+1;
        p[i].is_completed = 0;
    }

    int time = 0, completed = 0;
    while(completed != n) {
        int highest_priority = -1, index = -1;
        for(i=0; i<n; i++) {
            if(!p[i].is_completed && p[i].arrival_time <= time) {
                if(p[i].priority > highest_priority) {
                    highest_priority = p[i].priority;
                    index = i;
                }
            }
        }
        if(index != -1) {
            p[index].waiting_time = time - p[index].arrival_time;
            p[index].turnaround_time = p[index].waiting_time + p[index].burst_time;
            avg_waiting_time += p[index].waiting_time;
            avg_turnaround_time += p[index].turnaround_time;
            p[index].is_completed = 1;
            completed++;
            time += p[index].burst_time;
        } else {
            time++;
        }
    }

    // print result
    printf("\nProcess\tArrival Time\tBurst Time\tPriority\tWaiting Time\tTurnaround Time\n");
    for(i=0; i<n; i++) {
        printf("%d\t\t%d\t\t%d\t\t%d\t\t%d\t\t%d\n", p[i].pid, p[i].arrival_time, p[i].burst_time, p[i].priority, p[i].waiting_time, p[i].turnaround_time);
    }
    avg_waiting_time /= n;
    avg_turnaround_time /= n;
    printf("Average Waiting Time: %f\n", avg_waiting_time);
    printf("Average Turnaround Time: %f\n", avg_turnaround_time);

    return 0;
}

用C语言模拟实现先来先服务、短作业优先、优先级和时间片轮转等操作系统中的进程调度算法。

好的，我可以为您解答这个问题。

首先，需要明确一下进程调度算法的概念。进程调度算法是操作系统用来决定哪个进程可以获得 CPU 时间片的一种策略。常见的调度算法有先来先服务、短作业优先、优先级和时间片轮转等。

下面，我将分别介绍这些调度算法在 C 语言中的模拟实现。

1. 先来先服务调度算法

先来先服务调度算法是最简单的调度算法，它按照进程到达的先后顺序进行调度。实现该算法的代码如下：

#include <stdio.h>

int main() {
    int n, i, j;
    float bt[20], wt[20], tat[20], avwt = 0, avtat = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);

    printf("Enter the burst time for each process:\n");
    for(i = 0; i < n; i++) {
        printf("Process %d: ", i + 1);
        scanf("%f", &bt[i]);
    }

    wt[0] = 0;
    for(i = 1; i < n; i++) {
        wt[i] = 0;
        for(j = 0; j < i; j++)
            wt[i] += bt[j];
    }

    printf("\nProcess\t  Burst Time\t  Waiting Time\t  Turnaround Time");

    for(i = 0; i < n; i++) {
        tat[i] = bt[i] + wt[i];
        avwt += wt[i];
        avtat += tat[i];
        printf("\n   %d\t\t%5.2f\t\t%5.2f\t\t%5.2f", i + 1, bt[i], wt[i], tat[i]);
    }

    avwt /= i;
    avtat /= i;
    printf("\n\nAverage Waiting Time: %5.2f", avwt);
    printf("\nAverage Turnaround Time: %5.2f", avtat);

    return 0;
}

2. 短作业优先调度算法

短作业优先调度算法是按照进程的执行时间长短来进行调度的。实现该算法的代码如下：

#include <stdio.h>

int main() {
    int n, i, j, pos, temp;
    float bt[20], wt[20], tat[20], avwt = 0, avtat = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);

    printf("Enter the burst time for each process:\n");
    for(i = 0; i < n; i++) {
        printf("Process %d: ", i + 1);
        scanf("%f", &bt[i]);
    }

    for(i = 0; i < n; i++) {
        pos = i;
        for(j = i + 1; j < n; j++) {
            if(bt[j] < bt[pos])
                pos = j;
        }

        temp = bt[i];
        bt[i] = bt[pos];
        bt[pos] = temp;
    }

    wt[0] = 0;
    for(i = 1; i < n; i++) {
        wt[i] = 0;
        for(j = 0; j < i; j++)
            wt[i] += bt[j];
    }

    printf("\nProcess\t  Burst Time\t  Waiting Time\t  Turnaround Time");

    for(i = 0; i < n; i++) {
        tat[i] = bt[i] + wt[i];
        avwt += wt[i];
        avtat += tat[i];
        printf("\n   %d\t\t%5.2f\t\t%5.2f\t\t%5.2f", i + 1, bt[i], wt[i], tat[i]);
    }

    avwt /= i;
    avtat /= i;
    printf("\n\nAverage Waiting Time: %5.2f", avwt);
    printf("\nAverage Turnaround Time: %5.2f", avtat);

    return 0;
}

3. 优先级调度算法

优先级调度算法是按照进程的优先级来进行调度的。实现该算法的代码如下：

#include <stdio.h>

int main() {
    int n, i, j, pos, temp, priority[20];
    float bt[20], wt[20], tat[20], avwt = 0, avtat = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);

    printf("Enter the burst time and priority for each process:\n");
    for(i = 0; i < n; i++) {
        printf("Process %d: ", i + 1);
        scanf("%f %d", &bt[i], &priority[i]);
    }

    for(i = 0; i < n; i++) {
        pos = i;
        for(j = i + 1; j < n; j++) {
            if(priority[j] < priority[pos])
                pos = j;
        }

        temp = priority[i];
        priority[i] = priority[pos];
        priority[pos] = temp;

        temp = bt[i];
        bt[i] = bt[pos];
        bt[pos] = temp;
    }

    wt[0] = 0;
    for(i = 1; i < n; i++) {
        wt[i] = 0;
        for(j = 0; j < i; j++)
            wt[i] += bt[j];
    }

    printf("\nProcess\t  Burst Time\t  Waiting Time\t  Turnaround Time");

    for(i = 0; i < n; i++) {
        tat[i] = bt[i] + wt[i];
        avwt += wt[i];
        avtat += tat[i];
        printf("\n   %d\t\t%5.2f\t\t%5.2f\t\t%5.2f", i + 1, bt[i], wt[i], tat[i]);
    }

    avwt /= i;
    avtat /= i;
    printf("\n\nAverage Waiting Time: %5.2f", avwt);
    printf("\nAverage Turnaround Time: %5.2f", avtat);

    return 0;
}

4. 时间片轮转调度算法

时间片轮转调度算法是按照时间片的大小来分配 CPU 时间的。实现该算法的代码如下：

#include <stdio.h>

int main() {
    int n, i, j, time_quantum;
    float bt[20], rem_bt[20], wt[20], tat[20], avwt = 0, avtat = 0;

    printf("Enter the number of processes: ");
    scanf("%d", &n);

    printf("Enter the burst time for each process:\n");
    for(i = 0; i < n; i++) {
        printf("Process %d: ", i + 1);
        scanf("%f", &bt[i]);
        rem_bt[i] = bt[i];
    }

    printf("Enter the time quantum: ");
    scanf("%d", &time_quantum);

    int t = 0;
    while(1) {
        int done = 1;
        for(i = 0; i < n; i++) {
            if(rem_bt[i] > 0) {
                done = 0;
                if(rem_bt[i] > time_quantum) {
                    t += time_quantum;
                    rem_bt[i] -= time_quantum;
                } else {
                    t += rem_bt[i];
                    wt[i] = t - bt[i];
                    rem_bt[i] = 0;
                }
            }
        }
        if(done == 1) break;
    }

    for(i = 0; i < n; i++) {
        tat[i] = bt[i] + wt[i];
        avwt += wt[i];
        avtat += tat[i];
    }

    avwt /= i;
    avtat /= i;
    printf("\n\nAverage Waiting Time: %5.2f", avwt);
    printf("\nAverage Turnaround Time: %5.2f", avtat);

    return 0;
}

以上就是 C 语言模拟实现先来先服务、短作业优先、优先级和时间片轮转等操作系统中的进程调度算法的代码实现。