Operating Systems Lab Programs

1.Write a C program to find total and average of student’s marks by entering name, rollno, branch and six subjects marks.

AIM:


Source Code

#include <stdio.h>

int main()

{

    char name[20],rollno[10],branch[3];

    int sub[6],i,n,s,j,tot=0,avg=0;

    printf("how many students data u need to enter ");

    scanf("%d",&n);

    printf("now enter the students details \n");

    for (i=0;i<n;i++)

    {

        printf("Enter the name of the student");

        scanf("%s",name);

        printf("Enter the rollno of the student");

        scanf("%s",rollno);

        printf("Enter the branch of the student");

        scanf("%s",branch);

        printf(" how many subjects marks u want to enter");

        scanf("%d",&s);

        for(j=0;j<s;j++)

        {

        printf("subject marks of the student%d",j+1);

        scanf("%d",&sub[j]);

        tot=tot+sub[j];

        }

        printf("\n Total marks of the student %d %d\n",i+1,tot);

        avg=tot/s;

        printf("Average of the marks of the student %d %d \n",i+1,avg);

    }

    printf("\n successfully Completed\n");

    return 0;

}

2.First Come First Served Scheduling Algorithm

AIM:


Source Code

#include<stdio.h>

#include<conio.h>

void main()

{

int n,a[10],b[10],t[10],w[10],c[10],i,m;

float  att=0,awt=0;

clrscr();

for(i=0;i<10;i++)

{

a[i]=0; b[i]=0; w[i]=0; c[i]=0;

}

printf("enter the number of process");

scanf("%d",&n);

printf("enter the arrival times burst times");

for(i=0;i<n;i++)

scanf("%d %d",&a[i],&b[i]);

c[0]=0;

for(i=0;i<n;i++)

c[i+1]=c[i]+b[i];

for(i=0;i<n;i++)

{

t[i]=c[i+1]-a[i];

w[i]=t[i]-b[i];

awt=awt+w[i];

att=att+t[i];

}

awt =awt/n;

att=att/n;

printf("\n\tprocess\tarrival time \twaiting time\tturn arround time\n");

for(i=0;i<n;i++)

{

printf("\tp%d\t\t%d\t\t%d\t\t%d\n",i,a[i],w[i],t[i]);

}

printf("the average waiting time is %f\n",awt);

printf("the average turn around time is %f\n",att);

getch();

}

3.Shortest Job First Scheduling Algorithm

AIM:


Source Code

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

int bt[20],at[10],n,i,j,temp,st[10],ft[10],wt[10],ta[10];

int totwt=0,totta=0;

float awt,ata;

char pn[10][10],t[10];

clrscr();

printf("Enter the number of process:");

scanf("%d",&n);

for(i=0;i<n;i++)

{

printf("Enter process name, arrival time & burst time:");

flushall();

scanf("%s%d%d",pn[i],&at[i],&bt[i]);

}

for(i=0;i<n;i++)

for(j=0;j<n;j++)

{

if(bt[i]<bt[j])

{

temp=at[i];

at[i]=at[j];

at[j]=temp;

temp=bt[i];

bt[i]=bt[j];

bt[j]=temp;

strcpy(t,pn[i]);

strcpy(pn[i],pn[j]);

strcpy(pn[j],t);

}

}

for(i=0;i<n;i++)

{

if(i==0)

          st[i]=at[i];

else st[i]=ft[i-1];

wt[i]=st[i]-at[i];

ft[i]=st[i]+bt[i];

ta[i]=ft[i]-at[i];

totwt+=wt[i];

totta+=ta[i];

}

awt=(float)totwt/n;

ata=(float)totta/n;

printf("\nPname\tarrivaltime\tbursttime\twaitingtime\ttatime");

for(i=0;i<n;i++)

printf("\n%s\t%5d\t\t%5d\t\t%5d\t\t%5d",pn[i],at[i],bt[i],wt[i],ta[i]);

printf("\nAverage waiting time is:%f",awt);

printf("\nAverage turnaroundtime is:%f",ata);

getch();

}