操作系统实验之单处理机系统的进程调度

过程：假设进入的进程有3个，轮转时间片为5，每经过一个时间片要么优先级发生变化（在我的实验中加2，也就是优先级降低两个等级），要么该进程结束（删除节点）。

运行逻辑如下：
初始化：

根据优先级排序：

第一个时间片轮转后：

第二个时间片轮转后：

第三个时间片轮转后：

第四个时间片轮转后：

第五个时间片轮转后所有节点均被删除。
代码：

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

typedef struct pcb
{ 
   
    int name;                 //进程名
    int status;               //进程状态
    int priority;             //进程优先级
    int time;                 //进程所需运行时间
    struct pcb *next;         //指向下一个节点
}pcb;

int M;
pcb *creat(int count, pcb *head)   //count为进程数
{ 
   
    pcb *q, *p;
    head = (pcb *)malloc(sizeof(pcb)); //头指针
    p = head;
    int i = 0;
    for(i = 0; i < count; i++)
	{ 
   
        q = (pcb *)malloc(sizeof(pcb));
        printf("input %d process name: ", i+1);
        scanf("%d", &q->name);
        printf("input %d process priority: ", i+1);
        scanf("%d", &q->priority);
        printf("input %d process time: ", i+1);
        scanf("%d", &q->time);
        q->status = 1; //默认进程为就绪态
        p->next = q;
        p = q;
    }
    p->next = NULL;
    return head;
}

void Sort1(pcb *head)
{ 
   
    pcb * q, *p, *tail, *temp;
    tail = NULL;
    q = head;
    while((head->next) != tail)
	{ 
   
        p = head->next;
        q = head;
        while(p->next != tail)
		{ 
   
	        if((p->priority) > (p->next->priority)){ 
   
	            q->next = p->next;
	            temp = p->next->next;
	            p->next->next = p;
	            p->next = temp;
	            p = q->next;
	        }
	        p = p->next;
	        q = q->next;
    	}
    	tail = p;
    }

}

void Print(pcb *head)
{ 
   
	pcb *ptr = head->next;
    while(ptr != NULL){ 
   
          printf("name = %d, pro = %d, status = %d, time = %d\n", ptr->name,ptr->priority, ptr->status, ptr->time);
          ptr = ptr->next;
    }
}

pcb *sch(pcb *head){ 
   
    pcb * ptr = head->next;
    while(ptr != NULL){ 
    //有进程
        printf("name = %d, pro = %d, status = %d, time = %d\n", ptr->name, ptr->priority, ptr->status, ptr->time);

        ptr->priority = ptr->priority + 2;

        ptr->time = ptr->time - M;
        if(ptr->time > 0) { 
   
            Sort1(head);
        } else { 
   
	    ptr->time = 0;
            ptr->status = 0;
            head->next = ptr->next; //进程结束，删除
        }

	printf("list:\n");
	Print(head);
	printf("\n\n");    

	ptr = head->next;
    }
    return head;
}

int main()
{ 
   
    int num;
    pcb *head;
    printf("please enter the size of the time slice:");
    scanf("%d", &M);
    printf("Number of input processes:");
    scanf("%d",&num);

    head = creat(num, head);
    printf("\n");
	Print(head);

    printf("\n\nstart:\n");
    Sort1(head);
    sch(head);
    return 0;
}

结果：