多道系统中多进程并发执行，为了提高系统性能解决进程死锁问题，进程的优先级是动态变化的。正在执行的进程优先级会随时间降低，而挂起的进程或等待的进程的优先级会逐渐升高，这样就解决了操作系统中一个地优先级程序长期占据cpu，而高优先级进程却迟迟不能得到处理。
这是我最近使用tc2.0图形界面对该算法进行模拟的源代码，所有代码都放在一个文件里了。
今天发现有的blog转载了本blog的文章，我非常欢迎，但请您注明转载自这里，这样也为我的blog做一下广告，谢谢！
#include <time.h>
#include <dos.h>
#include <math.h>
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <graphics.h>
#define ESC 0x1b
#define ENTER 0x0d
#define TRUE 1
#define FALSE 0
/*每隔TIME秒就变换一次优先级*/
#define TIME 5
/*数据结构*/
/****************************************************************/
enum _Status/*进程状态枚举*/
{
READY =0,/*就绪*/
RUN,/*执行中*/
SUSPEND,/*挂起*/
};
typedef enum _Status Status;
/****************************************************************/
struct _Pcb/*进程结构*/
{
int PID;/*进程ID，ID为负数的进程为系统后备队列的作业*/
int Time;/*进程运行需要的时间*/
int Prior;/*进程的优先级，越大越优先*/
Status Sts;/*状态*/
struct _Pcb *Next;/*指向本进程队列中下个进程的PCB*/
};
typedef struct _Pcb PCB;
/****************************************************************/
struct _Batch/*多道处理中的道结构*/
{
PCB *pcb;/*该道当前正在处理的进程*/
struct _Batch *Next;/*下一道*/
};
typedef struct _Batch Batch;
/****************************************************************/
/*多道系统相关全局变量*/
PCB *ProcQueue = NULL;/*进程链表，按优先级从大到小排列*/
Batch *BatchQueue = NULL;/*系统多道链表*/
/****************************************************************/
/*动态优先权抢占式调度算法及相关函数声明*/
/****************************************************************/
int InitBatchs(int n);/*初始化多道系统，n为道数*/
int InsertProc(int prior, int time);/*向进程链表中按优先级大小插入一个新进程*/
int InsertIDLE();/*向进程队列中加入后备进程，当系统空闲时将被调入*/
int SortProcQueue();/*将进程链表按优先级从大到小排列*/
int AddBatch();/*增加系统道数*/
int DeleteBatch();/*减少系统道数*/
int UnSuspendProc(int id);/*解除ID为id的进程的挂起状态*/
int UpdateBatchs();/*多道系统根据进程链表进行更新，并将执行完毕的进程删除*/
int PassSeconds(int n);/*系统经过n秒后计算数据并进行优先级调度*/
/****************************************************************/
/*各函数的定义*/
/****************************************************************/
int InitBatchs(int n)
{
int i;
for (i=0; i<n; ++i)
{
AddBatch();
}
return (UpdateBatchs());
}
int InsertProc(int prior, int time)
{
static int sysid = 0;/*该系统已经加入过多少进程，此值将是新进程的ID*/
PCB *last,*now,*pcb;
pcb = (PCB*)malloc(sizeof(PCB));
if (pcb == NULL) return FALSE;
pcb->Prior = prior;
pcb->Time = time;
pcb->PID = (++sysid);
pcb->Sts = READY;
if (ProcQueue == NULL)/*如果进程队列为空*/
{
ProcQueue = pcb;
pcb->Next = NULL;
return TRUE;
}
last = ProcQueue;
now = last->Next;
if (pcb->Prior > last->Prior)/*pcb将排在队头*/
{
pcb->Next = ProcQueue;
ProcQueue = pcb;
return TRUE;
}
while ((now != NULL) && (pcb->Prior < now->Prior))/*寻找插入位置*/
{
last = now;
now = last->Next;
}
last->Next = pcb;
pcb->Next = now;
return TRUE;
}
int InsertIDLE()
{
PCB *now = ProcQueue;
PCB *idle = (PCB*)malloc(sizeof(PCB));
if (idle == NULL) return FALSE;
idle->PID = -1;
idle->Prior = -1;
idle->Sts = SUSPEND;
idle->Time = -1;
idle->Next = NULL;
if (ProcQueue == NULL)
{
ProcQueue = idle;
return TRUE;
}
while(now->Next != NULL)
{
now = now->Next;
}
now->Next = idle;
return TRUE;
}
int SortProcQueue()
{ /*冒泡排序*/
PCB *last, *now;
int b = FALSE;/*上次遍历是否无交换产生*/
if (ProcQueue==NULL || ProcQueue->Next==NULL)/*如果链表中无进程或只有一个进程*/
return FALSE;
while (!b)
{
b = TRUE;
last=ProcQueue;
now=last->Next;
if (last->Prior < now->Prior)
{
ProcQueue = now;
last->Next = now->Next;
now->Next = last;
b = FALSE;
last = ProcQueue;
now = last->Next;
}
while (now->Next!=NULL)
{
if ((now->Prior)<(now->Next->Prior))
{
last->Next = now->Next;
now->Next = now->Next->Next;
last->Next->Next = now;
b = FALSE;
}
else
last = last->Next;
now = last->Next;
}
}
return TRUE;
}
int AddBatch()
{
Batch *bt = (Batch*)malloc(sizeof(Batch));
if (bt==NULL) return FALSE;
bt->Next = BatchQueue;
BatchQueue = bt;
bt->pcb = NULL;
return (InsertIDLE());
}
int DeleteBatch()
{
Batch *bt = BatchQueue;
PCB *last, *now;
if (BatchQueue==NULL || BatchQueue->Next==NULL)/*如果只剩最后一道则不删除*/
return FALSE;
if (ProcQueue==NULL || ProcQueue->Next==NULL)/*如果只有最后一个后备空闲进程*/
return FALSE;/**/
last = ProcQueue;
now = last->Next;
while (now->Next != NULL)/*查找到最后一个进程，该进程必定是后备空闲进程*/
{
last = now;
now = last->Next;
}
if (now==NULL || now->PID>=0)/*未查找到后备进程*/
return FALSE;/**/
free(now);
last->Next = NULL;
BatchQueue = BatchQueue->Next;
free(bt);
return TRUE;
}
int UnSuspendProc(int id)
{
PCB *now = ProcQueue;
if (ProcQueue==NULL) return FALSE;
while (now != NULL)
{
if (now->PID == id)
{
now->Sts = READY;
return TRUE;
}
}
return FALSE;
}
int UpdateBatchs()
{
Batch *bt = BatchQueue;
PCB *last = ProcQueue, *now;
while (bt != NULL)
{
bt->pcb = NULL;
bt = bt->Next;
}
if (ProcQueue == NULL) return TRUE;
while (last->Sts==RUN && last->PID>=0 && last->Time<=0)
{
ProcQueue = ProcQueue->Next;
free(last);
last = ProcQueue;
}
now = last->Next;
while (now != NULL)
{
if (now->Sts==RUN && now->PID>=0 && now->Time<=0)/*如果该进程是运行中的一般进程并已执行完毕*/
{
last->Next = now->Next;
free(now);
}
else
last = last->Next;
now = last->Next;
}
bt = BatchQueue;
now = ProcQueue;
while (bt != NULL && now != NULL)
{
bt->pcb = now;
now->Sts = RUN;
bt = bt->Next;
now = now->Next;
}
while (now != NULL)
{
if (now->Sts == RUN)
{
now->Sts = SUSPEND;
}
now = now->Next;
}
return TRUE;
}
int PassSeconds(int n)
{
static int time = 0;
int i=0, ProcEnd = FALSE;
PCB *pcb = ProcQueue;
Batch *bt = BatchQueue;
if (bt == NULL) return FALSE;
time += n;
if (time>=TIME)
{
i = time/TIME;/*经过多少时间段*/
time = time%TIME;
}
while (bt != NULL)/*更新进程运行时间*/
{
if (bt->pcb->PID>=0)
{
bt->pcb->Time -= n;
if (bt->pcb->Time <= 0)/*进程结束*/
{
ProcEnd = TRUE;
}
}
bt = bt->Next;
}
if (i > 0)
{
while (pcb != NULL)/*更新进程优先权（动态优先权）*/
{
if (pcb->Sts == RUN && pcb->PID>=0)/*运行的进程优先权降低*/
{
pcb->Prior -= i;
if (pcb->Prior < 0)
pcb->Prior = 0;
}
else if (pcb->Sts == SUSPEND && pcb->PID>=0)/*挂起的进程优先权升高*/
pcb->Prior += i;
pcb = pcb->Next;
}
}
if (i>0)
SortProcQueue();/*如果优先级有变动则重新排序*/
if (ProcEnd || i>0)
{
UpdateBatchs();/*更新多道进程*/
}
return TRUE;
}
/****************************************************************/
/*图形界面相关函数*/
/****************************************************************/
/*表格的单位宽度和高度*/
#define WIDTH 64
#define HEIGHT 12
void *black=NULL;/*背景色方格，使用它擦出表格中的图形*/
int InitGraph()/*初始化图形界面*/
{
int GraphDriver; /* The Graphics device driver */
int GraphMode; /* The Graphics mode value */
int ErrorCode;
GraphDriver = DETECT; /* Request auto-detection */
initgraph( &GraphDriver, &GraphMode, "" );
ErrorCode = graphresult(); /* Read result of initialization*/
if( ErrorCode != grOk )
{ /* Error occured during init */
printf(" Graphics System Error: %s\n", grapherrormsg( ErrorCode ) );
getch();
return FALSE;
}
cleardevice();
black = (void*)malloc(imagesize(1,1,WIDTH-1,HEIGHT-1));
getimage(1,1,WIDTH-1,HEIGHT-1,black);
DrawFrame();
DrawData();
return TRUE;
}
int DrawFrame()/*画边框和表头*/
{
settextjustify(CENTER_TEXT, CENTER_TEXT);
gprintf(320, HEIGHT/2-1, "Multi-Batch System Emulation");
settextjustify(LEFT_TEXT, TOP_TEXT);
moveto(0,HEIGHT);
lineto(0,479);
lineto(639,479);
lineto(639,HEIGHT);
lineto(0,HEIGHT);
line(WIDTH*4,HEIGHT,WIDTH*4,479);
line(WIDTH*7,HEIGHT,WIDTH*7,479);
line(0,HEIGHT*2,639,HEIGHT*2);
line(0,HEIGHT*3,639,HEIGHT*3);
gprintf(HEIGHT*0+2,HEIGHT*1+2,"System Batchs");/*系统多道列表头*/
gprintf(HEIGHT*0+2,HEIGHT*2+2,"Batch");
gprintf(WIDTH*1+2,HEIGHT*2+2,"ProcID");
gprintf(WIDTH*2+2,HEIGHT*2+2,"Time");
gprintf(WIDTH*3+2,HEIGHT*2+2,"Prior");
gprintf(WIDTH*4+2,HEIGHT*1+2,"Suspended Processes");/*挂起队列列表头*/
gprintf(WIDTH*4+2,HEIGHT*2+2,"ProcID");
gprintf(WIDTH*5+2,HEIGHT*2+2,"Time");
gprintf(WIDTH*6+2,HEIGHT*2+2,"Prior");
gprintf(WIDTH*7+2,HEIGHT*1+2,"Ready Processes");/*就绪队列列表头*/
gprintf(WIDTH*7+2,HEIGHT*2+2,"ProcID");
gprintf(WIDTH*8+2,HEIGHT*2+2,"Time");
gprintf(WIDTH*9+2,HEIGHT*2+2,"Prior");
}
int DrawData()/*绘制系统数据*/
{
int numRun=0, numSus=0, numRed=0;/*运行挂起和就绪的进程各有多少*/
PCB* now = ProcQueue;
int x=0, y=0;
while (now != NULL)
{
switch(now->Sts)
{
case RUN:
x = WIDTH*1;
y = HEIGHT*(3+(numRun++));
break;
case SUSPEND:
x = WIDTH*4;
y = HEIGHT*(3+(numSus++));
break;
case READY:
x = WIDTH*7;
y = HEIGHT*(3+(numRed++));
break;
}
if (now->Sts==RUN)/*该进程为正在运行的进程*/
{
putimage(x-WIDTH+1,y+1,black,COPY_PUT);
gprintf(x-WIDTH+2,y+2,"%d",numRun);
}
if (now->PID>=0)/*该进程不是后备进程*/
{
putimage(x+1,y+1,black,COPY_PUT);
gprintf(x+2,y+2,"%d",now->PID);
putimage(x+1+WIDTH,y+1,black,COPY_PUT);
gprintf(x+WIDTH+2,y+2,"%d",now->Time);
putimage(x+1+WIDTH*2,y+1,black,COPY_PUT);
gprintf(x+WIDTH*2+2,y+2,"%d",now->Prior);
}
else
{
putimage(x+1,y+1,black,COPY_PUT);
putimage(x+1+WIDTH,y+1,black,COPY_PUT);
putimage(x+1+WIDTH*2,y+1,black,COPY_PUT);
gprintf(x+2,y+2,"system idle process");
}
now = now->Next;
}
}
int DlgGetNum(char *buf,int l,int t,int r,int b,int gettime)
{
char ch;
int pos=0;
bar(l,t,r,b);
gprintf(l+10,t+5,"Add new Process");
if (gettime)
gprintf(l+10,t+20,"input the time:");
else
gprintf(l+10,t+20,"input the priority:");
while (1)
{
ch = getch();
if (ch == ENTER)/*如果输入了回车键*/
{
if(pos!=0)/*如果位置不在第一位(回车键不准第一个输入)*/
{
buf[pos]='\0';
break;
}
}
else if (ch>='0' && ch<='9')
{
buf[pos++]=ch;
buf[pos]='\0';
}
else if (ch == ESC)
{
return FALSE;
}
else/*其他按键均按BackSpace处理*/
{
--pos;
buf[pos]='\0';
}
if (pos<0)
{ pos=0; buf[pos]='\0';}
else if (pos>4)/*最多输入4位数*/
{ pos=4; buf[pos]='\0';}
bar(l,t+35,r,t+47);
gprintf(l+50,t+35,buf);
}
return TRUE;
}
int NewProcDlg()
{
int l=200,t=150,r=380,b=200,pos=0,prior=0,time=0;
char buf[5],ch;
PCB *pcb;
void* bg = (void*)malloc(imagesize(l,t,r,b));
getimage(l,t,r,b,bg);
setfillstyle(1,2);
flushall();
/*******输入优先级**********/
if (!DlgGetNum(buf,l,t,r,b,FALSE))
goto exit;
prior = atoi(buf);
/*******输入时间**********/
pos=0;
buf[pos]='\0';
if (!DlgGetNum(buf,l,t,r,b,TRUE))
goto exit;
time = atoi(buf);
InsertProc(prior, time);
exit:
putimage(l,t,bg,COPY_PUT);
free(bg);
return TRUE;
}
int gprintf( int xloc, int yloc, char *fmt, ... )/*图形系统中的格式输出*/
{
va_list argptr; /* Argument list pointer */
char str[140]; /* Buffer to build sting into */
int cnt; /* Result of SPRINTF for return */
va_start( argptr, format ); /* Initialize va_ functions */
cnt = vsprintf( str, fmt, argptr ); /* prints string to buffer */
outtextxy( xloc, yloc, str ); /* Send string in graphics mode */
va_end( argptr ); /* Close va_ functions */
return( cnt ); /* Return the conversion count */
}
/****************************************************************/
/*main函数*/
int main()
{
clock_t start=0, end=0;
char kb;
InitBatchs(3);/*初始化为3道系统*/
InitGraph();
while (1)
{
start = end = clock();
while (!kbhit())
{
start = clock();
if ((start-end)/18.2 >= 1)/*时间过了一秒*/
{
start = end = clock();
PassSeconds(1);
cleardevice();
DrawFrame();
DrawData();
}
}
kb = getch();
switch (kb)
{
case ESC:
closegraph();
return 0;
case 'w':
AddBatch();
UpdateBatchs();
cleardevice();
DrawFrame();
DrawData();
break;
case 's':
DeleteBatch();
UpdateBatchs();
cleardevice();
DrawFrame();
DrawData();
break;
case 'i':
NewProcDlg();
UpdateBatchs();
DrawFrame();
DrawData();
break;
}
}
return 0;
}
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