C - Program to Implement CPU Scheduling Algorithms
**********************************************************************************
Simulation of following CPU scheduling algorithms:
a. FCFS
b. SJF (preemptive and non-preemptive)
c. Priority Scheduling (preemptive and non-preemptive)
d. Round Robin Scheduling
**********************************************************************************
#include<stdio.h>
#include<stdlib.h>
#define MAX 20
typedef struct process
{
int BT,AT,TAT,WT,PNO,PID;
char name[10];
}process;
typedef struct RQ
{
process pr[MAX];
int f,r;
}RQ;
void get_PCB(process [],int *);
void FCFS(process [],int);
void sort_AT(process [],int);
void sort_BT(RQ []);
void disp_table(process [],int );
void SJF_NP(process [],int);
void SJF_P(process [],int);
void RR(process p[],int n,int);
float cal_avgwt(process [],int );
float cal_avgtat(process [],int );
void menu()
{
printf("\n\t\t****MENU*****");
printf("\n\t\t1. FCFS");
printf("\n\t\t2. SJF NP");
printf("\n\t\t3. RR");
printf("\n\t\t4. SJF P");
printf("\n\t\t5. EXIT");
printf("\n\t\tEnter Choice: \t");
}
void main()
{
int ch,TQ,n;
process P[MAX];
float avg_WT,avg_TAT;
clrscr();
printf("\nEnter Time Quantum");
scanf("%d",&TQ);
get_PCB(P,&n);
do
{
clrscr();
menu();
scanf("%d",&ch);
switch(ch)
{
case 1:
{
sort_AT(P,n);
FCFS(P,n);
disp_table(P,n);
avg_WT=cal_avgwt(P,n);
avg_TAT=cal_avgtat(P,n);
printf("\nAVERAGE WT : %f",avg_WT);
printf("\nAVERAGE TAT : %f",avg_TAT);
break;
}
case 2:
{
SJF_NP(P,n);
disp_table(P,n);
avg_WT=cal_avgwt(P,n);
avg_TAT=cal_avgtat(P,n);
printf("\nAVERAGE WT : %f",avg_WT);
printf("\nAVERAGE TAT : %f",avg_TAT);
break;
}
case 3:
{
RR(P,n,TQ);
disp_table(P,n);
avg_WT=cal_avgwt(P,n);
avg_TAT=cal_avgtat(P,n);
printf("\nAVERAGE WT : %f",avg_WT);
printf("\nAVERAGE TAT : %f",avg_TAT);
break;
}
case 4:
{
SJF_P(P,n);
disp_table(P,n);
avg_WT=cal_avgwt(P,n);
avg_TAT=cal_avgtat(P,n);
printf("\nAVERAGE WT : %f",avg_WT);
printf("\nAVERAGE TAT : %f",avg_TAT);
break;
}
case 5:
break;
}
getch();
}while(ch!=5);
}
float cal_avgwt(process p[],int n)
{
float avg=0;
int i;
for(i=0;i<n;i++)
{
avg+=p[i].WT;
}
avg=avg/n;
return avg;
}
float cal_avgtat(process p[],int n)
{
float avg=0;
int i;
for(i=0;i<n;i++)
{
avg+=p[i].TAT;
}
avg=avg/n;
return avg;
}
int get_first_process(process p[],int n)
{
int min,j,in;
min=p[0].AT;
for(j=0;j<n;j++)
{
if(p[j].AT<min)
{
in=j;
}
}
return in;
}
void check_arrival(RQ *r,process p[],int time,int n)
{
int i,j,flag=0;
for(i=0;i<n;i++)
{
for(j=0;j<=r->r;j++)
{
if(strcmp(p[i].name,r->pr[j].name)==0)
flag=1;
else
break;
}
if(p[i].AT == time && flag==0)
{
r->r=r->r + 1;
r->pr[r->r]=p[i];
}
flag=0;
}
}
void RR(process p[],int n,int tq)
{
int count=0,i,start,time=0;
RQ r;
r.f=r.r=-1;
start=get_first_process(p,n);
r.pr[0]=p[start];
r.f=r.r=0;
check_arrival(&r,p,time,n);
while(r.f!=-1)
{
for(count=0;count<tq;count++)
{
r.pr[r.f].BT--;
time++;
if(r.pr[r.f].BT==0)
break;
check_arrival(&r,p,time,n);
}
if(r.pr[r.f].BT!=0)
{
r.pr[r.r+1]=r.pr[r.f];
r.r++;
}
else
{
p[r.pr[r.f].PID].TAT=time - r.pr[r.f].AT;
p[r.pr[r.f].PID].WT=p[r.pr[r.f].PID].TAT - p[r.pr[r.f].PID].BT;
}
if(r.f==r.r)
r.f=r.r=-1;
else
r.f++;
}
}
void sort_BT(RQ *r)
{
int i,j;
process temp;
for(i=r->f;i<=r->r;i++)
{
for(j=i+1;j<=r->r;j++)
{
if(r->pr[j].BT<r->pr[i].BT)
{
temp=r->pr[j];
r->pr[j]=r->pr[i];
r->pr[i]=temp;
}
}
}
}
void SJF_NP(process p[],int n)
{
int time=0,start;
RQ r;
r.f=r.r=-1;
start=get_first_process(p,n);
r.pr[0]=p[start];
//p[start].WT=0;
//p[start].TAT=p[start].BT;
r.f=r.r=0;
check_arrival(&r,p,time,n);
while(r.f!=-1)
{
p[r.pr[r.f].PID].WT=time - r.pr[r.f].AT;
p[r.pr[r.f].PID].TAT=p[r.pr[r.f].PID].WT + r.pr[r.f].BT;
while(r.pr[r.f].BT != 0)
{
time++;
check_arrival(&r,p,time,n);
r.pr[r.f].BT--;
}
if(r.f==r.r)
r.f=r.r=-1;
else
r.f++;
sort_BT(&r);
}
}
int get_total_time(process p[],int n)
{
int i,sum=0;
for(i=0;i<n;i++)
{
sum+=p[i].BT;
}
return sum;
}
void SJF_P(process p[],int n)
{
int time=0,start,sum,i;
RQ r;
r.f=r.r=-1;
start=get_first_process(p,n);
r.pr[0]=p[start];
//p[start].WT=0;
//p[start].TAT=p[start].BT;
r.f=r.r=0;
check_arrival(&r,p,time,n);
sum=get_total_time(p,n);
for(i=0;i<sum;i++)
{
r.pr[r.f].BT--;
time++;
if(r.pr[r.f].BT==0)
{
p[r.pr[r.f].PID].TAT=time - r.pr[r.f].AT;
p[r.pr[r.f].PID].WT=p[r.pr[r.f].PID].TAT - p[r.pr[r.f].PID].BT;
r.f++;
}
check_arrival(&r,p,time,n);
sort_BT(&r);
}
}
void sort_AT(process p[],int n)
{
int i,j;
process temp;
for(i=0;i<n;i++)
{
for(j=i+1;j<n;j++)
{
if(p[j].AT<p[i].AT)
{
temp=p[j];
p[j]=p[i];
p[i]=temp;
}
}
}
}
void disp_table(process p[],int n)
{
int i;
printf("\n\n P_NAME \t AT \t BT \t WT \t TAT \t PNO");
for(i=0;i<n;i++)
{
printf("\n %-10s \t %d \t %d \t %d \t %d \t %d",p[i].name,p[i].AT,p[i].BT,p[i].WT,p[i].TAT,p[i].PNO);
}
}
void get_PCB(process p[],int *n)
{
int i;
printf("\n Enter total no of processes\n");
scanf("%d",n);
for(i=0;i<*n;i++)
{
printf("\n Enter Following details for Process %d",i+1);
printf("\n Name :\t");
scanf("%s",p[i].name);
printf("\n Arrival Time :\t");
scanf("%d",&p[i].AT);
printf("\n Burst Time :\t");
scanf("%d",&p[i].BT);
printf("\n Priority :\t");
scanf("%d",&p[i].PNO);
p[i].PID=i;
}
}
void FCFS(process p[],int n)
{
int i,j,sum=0;
p[0].TAT = p[0].BT;
p[0].WT = 0;
sum = p[0].BT;
for(i=1;i<n;i++)
{
p[i].WT=sum - p[i].AT;
p[i].TAT=p[i].WT + p[i].BT;
sum+=p[i].BT;
}
}
