在操作系统中，处理机调度是分配处理机资源给就绪队列中的进程，以实现系统的有效运行。调度算法的选择对系统性能有重大影响。常见的调度算法包括先来先服务（FCFS）、最短作业优先（SJF）、最短剩余时间优先（SRTF）和优先级调度等。

以下是一个简单的Python程序，用于模拟处理机调度的过程。我们将使用FCFS、SJF和SRTF三种调度算法进行仿真。

```python
import random
import time

定义一个进程类

class Process:
def init(self, pid, arrival_time, burst_time):
self.pid = pid
self.arrival_time = arrival_time
self.burst_time = burst_time
self.start_time = 0
self.end_time = 0
self.waiting_time = 0
self.turnaround_time = 0

FCFS调度算法

def fcfs(processes):
n = len(processes)
for i in range(n):
current_process = processes[i]
current_process.start_time = current_process.arrival_time
current_process.end_time = current_process.start_time + current_process.burst_time
current_process.waiting_time = current_process.arrival_time - current_process.start_time
current_process.turnaround_time = current_process.waiting_time + current_process.burst_time
processes[i] = current_process
return processes

SJF调度算法（此处简化为非抢占式SJF）

def sjf(processes):
n = len(processes)
processes.sort(key=lambda x: x.burst_time) # 按burst_time升序排序
for i in range(n):
current_process = processes[i]
current_process.start_time = current_process.arrival_time
current_process.end_time = current_process.start_time + current_process.burst_time
current_process.waiting_time = current_process.arrival_time - current_process.start_time
current_process.turnaround_time = current_process.waiting_time + current_process.burst_time
processes[i] = current_process
return processes

SRTF调度算法（此处简化为非抢占式SRTF）

def srtf(processes):
n = len(processes)
ready_queue = [] # 初始化就绪队列为空列表
current_time = 0 # 当前时间初始化为0
for i in range(n): # 遍历每个进程
current_process = processes[i] # 获取当前进程信息
if current_time < current_process.arrival_time: # 如果当前时间小于进程到达时间，则更新当前时间为进程到达时间
current_time = current_process.arrival_time
ready_queue.append(current_process) # 将当前进程加入就绪队列末尾
while ready_queue: # 当就绪队列非空时，执行以下操作
current_process = ready_queue[0] # 获取就绪队列头部进程信息
if current_process.arrival_time <= current_time: # 如果进程到达时间小于等于当前时间，则执行以下操作
current_process.start_time = current_time # 更新进程开始时间为当前时间
current_process.end_time = current_process.start_time + current_process.burst_time # 更新进程结束时间为进程执行时间加上当前时间
current_process.waiting_time = current_process.arrival_time - current_process.start_time # 更新进程等待时间为进程到达时间减去进程开始时间
current_process.turnaround_time = current_process.waiting_time + current_process.burst_time # 更新进程周转时间为进程等待时间加上进程执行时间
current_time += current_process.burst_time