用C模拟进程调度

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

#define randomize() srand((unsigned)time(NULL)) //定义一个宏


//PCB结构体定义部分
typedef struct PCB
{
	/** 进程标识符,取值1-5 **/
	unsigned int id;
	/** 进程优先级，随机产生，值1-5 **/
	signed int priority;
	/** 
		目前已占用的CPU时间数，
		初值为0；当该进程被调
		用执行时，每执行一个时
		间片，Used加1 
	**/
	unsigned int used;
	/** 
		进程尚需的CPU时间数，初值表示
		该进程需要运行的总时间，取值
		范围为5—10。并随机产生，每运
		行一个时间片need减1；need为0则
		进程结束。 
	**/
	unsigned int need;
	/**
		进程状态R（运行），W（就绪），F（完成）；
		初始时都处于就绪状态
	**/
	unsigned char status;
	/**
		指向就绪队列中下一个进程的PCB的指针
	**/
	struct PCB *next;
};

//程序入口主函数
int main(void)
{
	struct PCB process[5];
	int i=0;
	for(i;i<5;i++)
	{
		//初始化进程ID
		process[i].id = i+1;
		//初始化进程优先级
		process[i].priority = rand()%5+1;
		//初绐化已占用时间数
		process[i].used = 0;
		//初始化还要时间数(5-10)
		process[i].need = rand()%5+6;
		//初始化进程状态(就绪)
		process[i].status = 'W';
		//初始化指向下一个PCB的指针
		process[i].next = NULL;
		printf("process[%d]: id = %d",i+1,process[i].id);
		printf("  priority = %d",process[i].priority);
		printf("  used = %d",process[i].used);
		printf("  need = %d",process[i].need);
		printf("  status = %c",process[i].status);
		printf("  next = %s",process[i].next);
		printf("\n");
	}
	randomize();
	//形成一个按进程优先级从大到小排列的队列
	int j = 0;
	int k = 1;
	for(j;j<5;j++)
	{
		struct PCB temp;
		for(k=j+1;k<5;k++)
		{
			if(process[j].priority<process[k].priority)
			{
				temp = process[j];
				process[j] = process[k];
				process[k] = temp;
			}	
		}
		
	}
	printf("排序结果为：");
	for(i=0;i<4;i++)
	{
		printf(" %d ",process[i].priority);
		process[i].next = &process[i+1];
	}
	//初始化head,tail指针
	struct PCB *head = &process[0];
	struct PCB *tail = &process[4];
	struct PCB *run = head;
	tail->next = NULL;
	printf("\n初始化head,tail指针:");
	printf("head: %d ",head->priority);
	printf("tail: %d \n",(*tail).priority);
	printf("\n--------准备完成，开始调度---------\n");
	while(head!=NULL)
	{
		if(head == NULL)
			break;
		else
			run = head;
		run->priority--;
		run->status='R';
		run->used ++ ;
		if(run->need>0)
			run ->need -- ;
		head = head->next;
		printf("当前正在执行的进程ID：%d,status:%c,priority:%d,used:%d,need:%d\n"
			,run->id,run->status,run->priority,run->used,run->need);
		printf("时间片：");
		for(i=0;i<15000;i++)
		{
			int a=50000;
			while(a--);
			
			if(i%500==0)
				printf("#");
		}
		if(run->need > 0)
		{
			printf("   进入就绪队列\n");
			if(head->next == NULL)
				head = run;
			else
			{
				run->status='W';
				struct PCB *temp = head;
				struct PCB *pre = head;
				int flag = 1;
				while(flag)
				{
					if(temp!=tail && temp->priority < run->priority)
					{
						run->next = temp;
						pre->next = run;
						flag = 0;
					}
					if(temp==tail)
					{
						run->next = NULL;
						tail->next = run;
						tail = tail->next;
						flag = 0;
					}
					else
					{
						pre = temp;
						temp = temp->next;
					}	
				}
			}						
		}
		else
			printf("   完成\n");
		printf("\n");
	}
	return 0;
}