C Program to Simulate Round Robin CPU Sceduling Algorithm

The round robin CPU scheduling algorithm is simulated using C program. The time slice or time quantum is read from the user.

Program:

#include<stdio.h>
struct process{



int burst,wait,comp,f;
}p[20]={0,0};
int main(){
int
n,i,j,totalwait=0,totalturn=0,quantum,flag=1,
time=0;
printf("\nEnter The No Of Process
:");
scanf("%d",&n);
printf("\nEnter The Quantum time (in ms)
:");
scanf("%d",&quantum);
for(i=0;i<n;i++){
printf("Enter The Burst Time (in ms) For
Process #%2d :",i+1);
scanf("%d",&p[i].burst);
p[i].f=1;
}
printf("\nOrder Of Execution \n");
printf("\nProcess \tStarting\tEnding\tRemaining");
printf("\n\tTime \tTime\tTime");
while(flag==1){
flag=0;
for(i=0;i<n;i++){
if(p[i].f==1){
flag=1;
j=quantum;
if((p[i].burst-p[i].comp)>quantum){
p[i].comp+=quantum;
}
else{
p[i].wait=time-p[i].comp;
j=p[i].burst-p[i].comp;
p[i].comp=p[i].burst;
p[i].f=0;
}
printf("\nprocess # %-3d %-10d %-10d %-10d",i+1,time,time+j,p[i].burst-
p[i].comp);
time+=j;
}}}
printf("\n\n------------------");
printf("\nProcess \t Waiting Time  TurnAround Time ");
for(i=0;i<n;i++){
printf("\nProcess # %-12d%-15d%-15d",i+1,p[i].wait,p[i].wait+p[i].burst);
totalwait=totalwait+p[i].wait;
totalturn=totalturn+p[i].wait+p[i].burst;
}
printf("\n\nAverage\n------------------");
printf("\nWaiting Time : %f ms",totalwait/(float)n);
printf("\nTurnAround Time : %f ms\n\n",totalturn/(float)n);
return 0;
}

C Program to Simulate Priority Scheduling CPU scheduling Algorithm

The following C program implements Simulation of  priority scheduling (CPU Scheduling algorithm). Each process or job is given a priority. The priority is represented using a positive integer. The priority increases as the value of the integer decreases.

Program:

#include<stdio.h>
struct process{



int burst,wait,no,priority;
}p[20]={0,0};
int main(){
int n,i,j,totalwait=0,totalturn=0;
printf("\nEnter The No Of Process :");
scanf("%d",&n);
for(i=0;i<n;i++){
printf("Enter The Burst Time (in ms) For Process #%2d :",i+1);
scanf("%d",&p[i].burst);
printf("Enter The Priority For Process #%2d :",i+1);
scanf("%d",&p[i].priority);
p[i].no=i+1;
}
for(i=0;i<n;i++)
for(j=0;j<n-i-1;j++)
if(p[j].priority>p[j+1].priority)
{
p[j].burst^=p[j+1].burst^=p[j].burst^=p[j+1].burst;
p[j].no^=p[j+1].no^=p[j].no^=p[j+1].no;
//Simple way to swap 2 var’s
p[j].priority^=p[j+1].priority^=p[j].priority^=p[j+1].priority;
//printf("j");
}
printf("\nProcess \t Starting\tEnding\tWaiting\tTurnAround ");
printf("\n\t Time\tTime\tTime\tTime ");
for(i=0;i<n;i++)
{
printf("\nProcess # %-11d%-10d%-10d%-10d%10d",p[i].no,p[i].wait,p[i].wait+p[i].burst,p[i].wait,p[i].wait+p[i].burst);
p[i+1].wait=p[i].wait+p[i].burst;
totalwait=totalwait+p[i].wait;
totalturn=totalturn+p[i].wait+p[i].burst;
}
printf("\n\nAverage\n---------");
printf("\nWaiting Time : %f ms",totalwait/(float)n);
printf("\nTurnAround Time : %f ms\n\n",totalturn/(float)n);
return 0;
}

Output:
Enter The No Of Process :3
Enter The Burst Time (in ms) For Process #1 :30
Enter The Priority For Process # 1 :2
Enter The Burst Time (in ms) For Process #2 :20
Enter The Priority For Process # 2 :1
Enter The Burst Time (in ms) For Process #3 :40
Enter The Priority For Process # 3 :3

Process          Starting  Ending  Waiting  TurnAround
                          Time        Time      Time          Time
Process # 2        0             20           0                20
Process # 1       20            50          20              50
Process # 3       50            90          50              90

Average
---------
Waiting Time : 23.333333 ms
TurnAround Time : 53.333333 ms

Simulation of Shortest Job First (SJF) CPU scheduling algorithm in C Language

This is a C program to simulate Shortest Job First (SJF) CPU scheduling algorithm. In Shortest Job first CPU scheduling algorithm, the process with  shortest CPU burst time is executed first. The following program is to simulate non preemptive SJF scheduling. Preemptive SJF CPU scheduling algorithm will be discussed in another post.

#include<stdio.h>
struct process
{
int burst,wait,no;
}p[20]={0,0};

int main()
{
int n,i,j,totalwait=0,totalturn=0;
printf("\nEnter The No Of Process :");
scanf("%d",&n);
for(i=0;i<n;i++)
  {
  printf("Enter The Burst Time (in ms) For Process #%2d :",i+1);
  scanf("%d",&p[i].burst);
  p[i].no=i+1;
  }

for(i=0;i<n;i++)
  for(j=0;j<n-i-1;j++)
    if(p[j].burst>p[j+1].burst)
      {
      p[j].burst^=p[j+1].burst^=p[j].burst^=p[j+1].burst;
      p[j].no^=p[j+1].no^=p[j].no^=p[j+1].no;
      }

printf("\nProcess \t Waiting Time TurnAround Time ");
for(i=0;i<n;i++)
  {
  printf("\nProcess # %-12d%-15d%-15d",p[i].no,p[i].wait,p[i].wait+p[i].burst);
  p[i+1].wait=p[i].wait+p[i].burst;
  totalwait=totalwait+p[i].wait;
  totalturn=totalturn+p[i].wait+p[i].burst;
  }
printf("\n\nAverage\n---------");
printf("\nWaiting Time : %f ms",totalwait/(float)n);
printf("\nTurnAround Time : %f ms\n\n",totalturn/(float)n);
return 0;

}

Output:

Enter The No Of Process :3
Enter The Burst Time (in ms) For Process # 1 :20
Enter The Burst Time (in ms) For Process # 2 :30
Enter The Burst Time (in ms) For Process # 3 :10
Process          Waiting Time     TurnAround Time
Process # 3          0                           10
Process # 1        10                            30
Process # 2        30                            60

Average---------
Waiting Time : 13.333333 ms
TurnAround Time : 33.333333 ms

Related Posts:

C Program to Simulate ls Command in Linux
C Program to Simulate Round Robin CPU Scheduling Algorithm
C Program to Simulate Priority CPU Scheduling Algorithm
C Program to Simulate First Come First Serve (FCFS) CPU Scheduling Algorithm
C Program to Simulate rmdir Command or Delete Directory
C Program to Open, Read and Write Files
C Program to Create Process and Display Process ID - OS Lab Program
How to Use Fork and Exec System Calls
How to Use Exit System Call
C Program to make Parent Process Wait for Child to Terminate
C Program to Simulate GREP Command in Linux
C Program to make Child Process an Orphan Process
C Program to Show Process ID in Linux
C Program for Inter Process Communication using Pipes or Named Pipes (Chat Program)
C Program to Create a Process Using Fork System Call

Simulation of FCFS CPU Scheduling Algorithm in C

This is a C program to simulate First come first served (FCFS) CPU scheduling algorithm. First come first served algorithm serves each processes (or jobs) in the order of arrival. The process with lowest arrival time is executed first.

Program:
#include<stdio.h>
struct process
{
int burst,wait;
}p[20]={0,0};



int main()
{
int n,i,totalwait=0,totalturn=0;
printf("\nEnter The No Of Process :");
scanf("%d",&n);
for(i=0;i<n;i++)
{
printf("Enter The Burst Time (in ms) For Process #%2d :",i+1);
scanf("%d",&p[i].burst);
}
printf("\nProcess \t Waiting Time\tTurnAround Time ");
printf("\n\t (in ms)\t(in ms)");
for(i=0;i<n;i++)
{
printf("\nProcess # %-12d%-15d%-15d",i+1,p[i].wait,p[i].wait+p[i].burst);
p[i+1].wait=p[i].wait+p[i].burst;
totalwait=totalwait+p[i].wait;
totalturn=totalturn+p[i].wait+p[i].burst;
}
printf("\n\nAVERAGE\n--------- ");
printf("\nWaiting Time : %f ms",totalwait/(float)n);
printf("\nTurnAround Time : %f ms\n\n",totalturn/(float)n);
return 0;
}

Output:
Enter The No Of Process :3
Enter The Burst Time (in ms) For Process # 1 :10
Enter The Burst Time (in ms) For Process # 2 :30
Enter The Burst Time (in ms) For Process # 3 :20
Process    Waiting Time     Turn Around Time
                     (in ms)                      (in ms)
Process # 1     0                               10
Process # 2    10                              40
Process # 3    40                              60

AVERAGE
---------
Waiting Time : 16.666667 ms
TurnAround Time : 36.666667 ms

C Program to Simulate the ls Command in Linux Operating system

This is a c program to do Simulation of ls Command in linux. The ls command lists all the contents of the directory including filse and sub-directories. The following c program in simulates the ls command.

#include<stdio.h>
#include<dirent.h>
main()
{
char dirname[10];
DIR*p;
struct dirent *d;
printf("Enter directory name\n");
scanf("%s",dirname);
p=opendir(dirname);
if(p==NULL)
  {
  perror("Cannot find directory");
  exit(-1);
  }
while(d=readdir(p))
  printf("%s\n",d->d_name);
}

Related Posts:

C Program to Simulate ls Command in Linux
C Program to Simulate Round Robin CPU Scheduling Algorithm
C Program to Simulate Priority CPU Scheduling Algorithm
C Program to Simulate First Come First Serve (FCFS) CPU Scheduling Algorithm
C Program to Simulate rmdir Command or Delete Directory
C Program to Open, Read and Write Files
C Program to Create Process and Display Process ID - OS Lab Program
How to Use Fork and Exec System Calls
How to Use Exit System Call
C Program to make Parent Process Wait for Child to Terminate
C Program to Simulate GREP Command in Linux
C Program to make Child Process an Orphan Process
C Program to Show Process ID in Linux
C Program for Inter Process Communication using Pipes or Named Pipes (Chat Program)
C Program to Create a Process Using Fork System Call

C Program to Simulate grep Command in Linux

This post contains C program to simulate grep command in Linux or Unix operating systems

Simulation of  grep command in Linux

#include<stdio.h>
#include<string.h>
void main()
{
char fn[10],pat[10],temp[200];
FILE *fp;
printf("Enter file name\n");
scanf("%s",fn);
printf("Enter pattern to be searched\n");
scanf("%s",pat);
fp=fopen(fn,"r");
while(!feof(fp))
{
fgets(temp,1000,fp);
if(strstr(temp,pat))
  printf("%s",temp);
}
fclose(fp);
}

Related Posts:

C Program to Simulate ls Command in Linux
C Program to Simulate Round Robin CPU Scheduling Algorithm
C Program to Simulate Priority CPU Scheduling Algorithm
C Program to Simulate Shortest Job First (SJF) CPU Scheduling Algorithm
C Program to Simulate First Come First Serve (FCFS) CPU Scheduling Algorithm
C Program to Simulate rmdir Command or Delete Directory
C Program to Open, Read and Write Files
C Program to Create Process and Display Process ID - OS Lab Program
How to Use Fork and Exec System Calls
How to Use Exit System Call
C Program to make Parent Process Wait for Child to Terminate
C Program to make Child Process an Orphan Process
C Program to Show Process ID in Linux
C Program for Inter Process Communication using Pipes or Named Pipes (Chat Program)
C Program to Create a Process Using Fork System Call

C Program to Remove (Delete) a Directory using LINUX System Calls

This is a C program to delete  or remove a directory using the system calls in Linux or Unix operating systems. The program make use of the remove() system call in Linux.

#include<stdio.h>
#include<fcntl.h>
main()
{



char fn[10];
printf("Enter source filename\n");
scanf("%s",fn);
if(remove(fn)==0)
printf("File removed\n");
else
printf("File cannot be removed\n");
}

C Program to open, read and write files and perform file copy operation usingSystem Calls in UNIX

Write a program to open, read and write files and perform file copy operation. This program show how to open, read, write and copy files using Linux or Unix system calls like open(), read() and write().

#include<stdio.h>
#include<fcntl.h>
main()
{


char buff[1000],fn1[10],fn2[10];
int fd1,fd2,n;
printf("Enter source filename\n");
scanf("%s",fn1);
printf("Enter destination file name\n");
scanf("%s",fn2);
fd1=open(fn1,O_RDONLY);
n=read(fd1,buff,1000);
fd2=open(fn2,O_CREAT|O_WRONLY);
n=write(fd2,buff,n);
close(fd1);
close(fd2);
}

C Program to Open, Read and Write a file using System Calls

This is a C program to open , read and write files using system calls in Linux (UNIX) operating systems. The system calls open(), read() and write() are used in the C program to open, read and write files in Unix/Linux operating systems.

#include<stdio.h>
#include<fcntl.h>
main()
{


char buff[100],fn[10];
int fd,n;
printf("Enter file name\n");
scanf("%s",fn);
fd=open(fn,O_RDONLY);
n=read(fd,buff,100);
n=write(1,buff,n);
close(fd);
}

Using System calls in C Program to rename a Directory in Linux

C Program to rename a directory in Unix or Linux operating systems using system call rename().

#include<stdio.h>
main()
{

char s[10],d[10];
printf("Enter source Dir Name:\n");
scanf("%s",s);
printf("Enter New Dir Name:\n");
scanf("%s",d);
if(rename(s,d)==-1)
perror("Can't be changed\n");
else
printf("%s is changed to %s\n\n",s,d);
}

How to Create process and display Process ID (pid) of Both Parent and Child

This program shows how to create process and display Process ID (pid) of Both Parent and Child processes. The process is created using the fork system call in UNIX (Linux) operating systems.

#include<stdio.h>
#include<dirent.h>
main(int argc,char **argv)
{

int pid,i;
for(i=0;i<atoi(argv[1]);i++)
{
pid=fork();
if(pid==0)
{
printf("child process id %d Parent process
id %d\n",getpid(),getppid());
}}}

How to use fork and exec System Call

Using fork and exec System calls in Linux (UNIX) operating systems. Fork system call is used to create a child process from a parent process.
#include<stdio.h>
main()
{

int pid;
pid=fork();
printf("%d\n",pid);
if(pid==0)
{
exec("/bin/date\n",NULL,NULL);
exit(0); }
else
{
printf("Parent process %d\n",pid); }}
if(sp)
while(dd=readdir(sp))
printf("--> %s\n",dd->d_name);
}
}

How to use exit() System call

C program to show how to use exit system call. The function exit() is used to exit from a process (or to terminate a process). This works both in Linux or UNIX and Windows operating systems.

#include<stdio.h>
main()
{

int pid;
pid=fork();
printf("%d\n",pid);
if(pid<0)
{
perror("Child can't be executed\n");
exit(-1);
}
else
{
printf("Child created\n");
exit(0);
}
}

How to make parent process wait till Completion of Child Process (Joining parent with child process)

How to make the parent process wait till the completion of execution of child process. The following C program makes the parent process to wait till the completion of its child process.

#include<stdio.h>
main()
{

int pid;
pid=fork();
printf("%d\n",pid);
if(pid==0)
{
printf("From child process \n");
}
else
{
wait(0);
printf("From parent process\n");
}
}

How to make Child process an Orphan Process

C program in Linux or Unix to make a child process orphan:

Making child as orphan

#include<stdio.h>
main()
{

int pid,pid1;
pid=fork();
if(pid>0)
{
printf("From parent process\n");
printf("Parent process %d \n",getpid());
}
else
{
sleep(1);
printf("From child process\n");
printf("child process %d \n",getpid());
}}

C Program to Show Process ID in Linux

This program is to show the process id (pid) in UNIX or Linx
The system call getpid() returns the process id of current process.

#include<stdio.h>
int main()
{
printf("\n Parent Process ID %d",getppid());
}

Inter Process Communication using Named Pipes - Chat Program in C

In this post, we will see a chat program using named pipes (fifo). Pipes are used for communication between processes. The named pipes are fifos. They enable two way communication unlike ordinary pipes. But they are half duplex, i.e. communication can take place only in one direction at a time. The program is in 3 parts: pipe_creation.c, leftTerminal.c and rightTerminal.c.

pipe_creation.c

#include<stdio.h>
void main()
{
int f1,f2;
f1 = mkfifo("pipeA",0666);
if(f1<0)
   printf("\npipeA was not created");
else
   printf("\npipeA created");

f2 = mkfifo("pipeB",0666);
if(f2<0)
   printf("\npipeB was not created");
else
   printf("\npipeB is created\n");
}

leftTerminal.c

#include<stdio.h> #include<fcntl.h> #include<string.h> #include<stdlib.h> void main() { char str[256]="start"; int fifo_write,fifo_read; while(strcmp(str,"end")!=0)   {   fifo_write= open("pipeA",O_WRONLY);   if(fifo_write<0)     printf("\nError opening pipe");   else     {     printf("\nEnter text:\n");     scanf("%s",str);     write(fifo_write,str,255*sizeof(char));     close(fifo_write);     }   fifo_read=open("pipeB",O_RDONLY);   if(fifo_read<0)     printf("\nError opening write pipe");   else     {     read(fifo_read,str,255*sizeof(char));     close(fifo_read);     printf("\n%s",str);     }   }

rightTerminal.c

#include<stdio.h> #include<fcntl.h> #include<string.h> #include<stdlib.h> void main() { char str[256]="start"; int fifo_read,fifo_write; while(strcmp(str,"end")!=0) { fifo_read=open("pipeA",O_RDONLY); if(fifo_read<0)    printf("\nError opening read pipe"); else    {    read(fifo_read,str,255*sizeof(char));    close(fifo_read);    printf("\n%s",str);    } fifo_write=open("pipeB",O_WRONLY); if(fifo_write<0)    printf("\nError opening write pipe"); else    {    printf("\nEnter text:\n");    scanf("%s",str);    write(fifo_write,str,255*sizeof(char));    close(fifo_write);    } } }

How to run:
Run pipe_creation.c first. Then close it. Then run leftTerm.c. Without closing it, open a new terminal window and run rightTerm.c. Start typing from leftTerm.c and then in rightTerm.c.

Output :
pipe_creation.c:
pipeA created
pipeB is created


leftTerminal.c 

Enter text:
hi

Hai
Enter text:
fine?

Ya.Sure
Enter text:
end


rightTerminal.c

hi
Enter text:
Hai

fine?
Enter text:
Ya.Sure

end
Enter text:
end

Related Posts:

C Program to Simulate ls Command in Linux
C Program to Simulate Round Robin CPU Scheduling Algorithm
C Program to Simulate Priority CPU Scheduling Algorithm
C Program to Simulate First Come First Serve (FCFS) CPU Scheduling Algorithm
C Program to Simulate rmdir Command or Delete Directory
C Program to Open, Read and Write Files
C Program to Create Process and Display Process ID - OS Lab Program
How to Use Fork and Exec System Calls
How to Use Exit System Call
C Program to make Parent Process Wait for Child to Terminate
C Program to Simulate GREP Command in Linux
C Program to make Child Process an Orphan Process
C Program to Show Process ID in Linux
C Program to Create a Process Using Fork System Call

Creating A Process in Linux (UNIX) - fork() Example Program

The system call fork() is used to  create a new process in UNIX based operating systems and Linux systems. The fork() system call creates a child process when called from a parent process. Unix will make an exact copy of the parent's address space and give it to the child. Therefore, the parent and child processes have separate address spaces. Here is a C program which uses the fork() system call to create a process during execution. The program is commented well for better understanding.

Program

/*The program (parent process) reads an array from the user.
It sorts it in descending order.


The child process created by parent process sorts it ascending order
*/

#include<stdlib.h>
#include<stdio.h>
int main()
{
  int cpid;
  int temp,a[100],n,i,j;
  printf("\nEnter number of elements : ");
  scanf("%d",&n);
  printf("Enter elements\n");
  for(i=0;i<n;i++){
     scanf("%d",&a[i]);
  }

printf("\n");
  cpid=fork(); /*Creating child process using fork() system call */

if(cpid<0)

{

printf("Cannot create a new process\n");

exit(0);

}
  if(cpid != 0)

{

/*fork returns processid of newly created process.
Therefore, the value of integer variable cpid in parent process is the process id of child process.
This block (if block) is executed only by the parent because the value of cpid is zero in child process. We use the value of variable cpid to decide which process (parent or child) should execute which part of code*/

  printf("\nThis is parent with id: %d\n",getpid());

/* The UNIX system call getpid() return the process id of process being executed.*/
     for(i=0;i<n;i++){
          for(j=0;j<n-1;j++){
                  if(a[j]<a[j+1]){
                     temp = a[j];
                     a[j] = a[j+1];
                     a[j+1] = temp;
                  }
          }
    }
 printf("Parent sorted the array in descending order\n");

}else

{

/*This block (else block) is executed only by the child process because value of cpid is zero only for child process.*/


    printf("\nThis is child with id: %d \n",getpid());
    for(i=0;i<n;i++){
          for(j=0;j<n-1;j++){
                  if(a[j]>a[j+1]){
                     temp = a[j];
                     a[j] = a[j+1];
                     a[j+1] = temp;
                  }
          }
     }
 printf("Child sorted the array in ascending order\n");

  }

/*The following part of code is executed by both the processes because it is not restricted using the value of cpid.*/

 for(i=0;i<n;i++){
    printf("%d\n",a[i]);
  }
   return 0;
}



Output:

Enter number of elements : 5
Enter elements
8
6
10
2
12


This is parent with id: 4261
Parent sorted the array in descending order
12
10
8
6
2

This is child with id: 4262
Child sorted the array in ascending order
2
6
8
10
12

Output of the program