shijianpian.c

简单轮转法的基本思想是：所有就绪进程按 FCFS排成一个队列

#include "stdio.h" 
#include <stdlib.h> 
#include <conio.h> 
#define getpch(type) (type*)malloc(sizeof(type)) 

struct pcb { 
char name[10]; 
char state; 
int ntime; 
int rtime; 
struct pcb* link; 
}*ready=NULL,*p; 
typedef struct pcb PCB;   
 sort() 
{ 
PCB *first, *second; 

if(ready==NULL) 
{ 
p->link=ready; 
ready=p; 
} 
else 
{ 
first=ready; 
second=first->link; 
while(second!=NULL) 
{ 

first=first->link; 
second=second->link; 

} 
 first->link=p; 
} 
}

input() 
{ 
int i,num; 
printf("\n 请输入进程个数?"); 
scanf("%d",&num); 
for(i=1;i<=num;i++) 
{ 
printf("\n 进程号No.%d:\n",i); 
p=getpch(PCB); 
printf("\n 输入进程名:"); 
scanf("%s",p->name); 

printf("\n 输入进程运行时间:"); 
scanf("%d",&p->ntime); 
printf("\n"); 
p->rtime=0;p->state='w'; 
p->link=NULL;
sort(); 
} 
} 
int space() 
{ 
int l=0; PCB* pr=ready; 
while(pr!=NULL) 
{ 
l++; 
pr=pr->link; 
} 
return(l); 
} 
disp(PCB * pr) 
{ 
printf("\n qname \t state  \t ndtime \t runtime \n"); 
printf("|%s\t",pr->name); 
printf("|%c\t",pr->state);
printf("|%d\t",pr->ntime); 
printf("|%d\t",pr->rtime); 
printf("\n"); 
}
output() 
{ 
PCB* pr; 
printf("\n **** 当前正在运行的进程是:%s",p->name);
disp(p); 
pr=ready; 
printf("\n ****当前就绪队列状态为:\n"); 
while(pr!=NULL) 
{ 
disp(pr); 
pr=pr->link; 
} 
} 
destroy() 
{ 
printf("\n 进程 [%s] 已完成.\n",p->name); 
free(p); 
} 
fcfs() 
{
(p->rtime)++; 
if(p->rtime==p->ntime) 
destroy();
else 
{ 

p->state='w'; 
sort(); 
} 
} 
main() 
{ 
int len,h=0; 
char ch; 
input(); 
len=space(); 
while((len!=0)&&(ready!=NULL)) 
{ 
ch=getchar();
h++; 
printf("\n 时间片第%d次轮转 \n",h); 
p=ready; 
ready=p->link; 
p->link=NULL; 
p->state='R'; 
output(); 
fcfs(); 
printf("\n 按任意键继续......"); 
ch=getchar(); 
} 
printf("\n\n 进程已经完成.\n"); 
ch=getchar(); 
}