#include<stdio.h>
#define MAX 20

int frames[MAX],ref[MAX],mem[MAX][MAX],faults,
sp,m,n,count[MAX];

void accept()
{
int i;

printf("Enter no.of frames:");
scanf("%d", &n);

printf("Enter no.of references:");
scanf("%d", &m);

printf("Enter reference string:\n");
for(i=0;i<m;i++)
{
printf("[%d]=",i);
scanf("%d",&ref[i]);
}
}

void disp()
{
int i,j;

for(i=0;i<m;i++)
printf("%3d",ref[i]);

printf("\n\n");

for(i=0;i<n;i++)
{
for(j=0;j<m;j++)
{
if(mem[i][j])
printf("%3d",mem[i][j]);
else
printf(" ");
}
printf("\n");
}

printf("Total Page Faults: %d\n",faults);
}

int search(int pno)
{
int i;

for(i=0;i<n;i++)
{
if(frames[i]==pno)
return i;
}

return -1;
}

int get_mfu(int sp)
{
int i,max_i,max=-9999;

i=sp;
do
{
if(count[i]>max)
{
max = count[i];
max_i = i;
}
i=(i+1)%n;
}while(i!=sp);

return max_i;
}

void mfu()
{
int i,j,k;
for(i=0;i<m && sp<n;i++)
{
k=search(ref[i]);
if(k==-1)
{
frames[sp]=ref[i];
count[sp]++;
faults++;
sp++;

for(j=0;j<n;j++)
mem[j][i]=frames[j];
}
else
count[k]++;
}
sp=0;
for(;i<m;i++)
{
k = search(ref[i]);
if(k==-1)
{
sp = get_mfu(sp);
frames[sp] = ref[i];
count[sp]=1;
faults++;
sp = (sp+1)%n;

for(j=0;j<n;j++)
mem[j][i] = frames[j];
}
else
count[k]++;
}
}
int main()
{
accept();
mfu();
disp();

return 0;
}

#include<stdio.h>
#define MAX 20
int frames[MAX],ref[MAX],mem[MAX][MAX],faults,sp,m,n;
void accept()
{
int i;
printf("Enter no.of frames:");
scanf("%d", &n);
printf("Enter no.of references:");
scanf("%d", &m);
printf("Enter reference string:\n");
for(i=0;i<m;i++)
{
printf("[%d]=",i);
scanf("%d",&ref[i]);
}
}
void disp()
{
int i,j;
for(i=0;i<m;i++)
printf("%3d",ref[i]);
printf("\n\n");
for(i=0;i<n;i++)
{
for(j=0;j<m;j++)
{
if(mem[i][j])
printf("%3d",mem[i][j]);
else
printf(" ");
}
printf("\n");
}
printf("Total Page Faults: %d\n",faults);
}
int search(int pno)
{
int i;
for(i=0;i<n;i++)
{
if(frames[i]==pno)
return i;
}
return -1;
}
void fifo()
{
int i,j;
for(i=0;i<m;i++)
{
if(search(ref[i])==-1)
{
frames[sp] = ref[i];
sp = (sp+1)%n;
faults++;
for(j=0;j<n;j++)
mem[j][i] = frames[j];
}
}
}
int main()
{
accept();
fifo();
disp();
return 0;
}

#include<stdio.h>
#define MAX 20
int frames[MAX],ref[MAX],mem[MAX][MAX],faults,
sp,m,n,time[MAX];
void accept()
{
int i;
printf("Enter no.of frames:");
scanf("%d", &n);
printf("Enter no.of references:");
scanf("%d", &m);
printf("Enter reference string:\n");
for(i=0;i<m;i++)
{
printf("[%d]=",i);
scanf("%d",&ref[i]);
}
}
void disp()
{
int i,j;
for(i=0;i<m;i++)
printf("%3d",ref[i]);
printf("\n\n");
for(i=0;i<n;i++)
{
for(j=0;j<m;j++)
{
if(mem[i][j])
printf("%3d",mem[i][j]);
else
printf(" ");
}
printf("\n");
}
printf("Total Page Faults: %d\n",faults);
}
int search(int pno)
{
int i;
for(i=0;i<n;i++)
{
if(frames[i]==pno)
return i;
}
return -1;
}
int get_lru()
{
int i,min_i,min=9999;
for(i=0;i<n;i++)
{
if(time[i]<min)
{
min = time[i];
min_i = i;
}
}
return min_i;
}
void lru()
{
int i,j,k;
for(i=0;i<m && sp<n;i++)
{
k=search(ref[i]);
if(k==-1)
{
frames[sp]=ref[i];
time[sp]=i;
faults++;
sp++;
for(j=0;j<n;j++)
mem[j][i]=frames[j];
}
else
time[k]=i;
}
for(;i<m;i++)
{
k = search(ref[i]);
if(k==-1)
{
sp = get_lru();
frames[sp] = ref[i];
time[sp] = i;
faults++;
for(j=0;j<n;j++)
mem[j][i] = frames[j];
}
else
time[k]=i;
}
}
int main()
{
accept();
lru();
disp();
return 0;
}

#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
void make_toks(char *s,char *tok[])
{
int i=0;
char *p;

p=strtok(s," ");//search f pattern fnmae
while(p!=NULL)
{
tok[i++]=p;
p=strtok(NULL," ");
}
tok[i]=NULL;
}
void search(char *fn,char op,char *pattern)
{
int fh,count=0,i=0,j=0;
char buff[255],c,*p;

fh=open(fn,O_RDONLY);
if(fh==-1)
{
printf("file %s not found",fn);
return;
}
switch(op)
{
case 'f': /*a.txt=*my name is
what is your name*/
while(read(fh,&c,1))
{
buff[j++]=c;//name
if(c=='\n')
{
buff[j]='\0';//name\0
j=0;
i++;
if(strstr(buff,pattern))
{
printf("%d: %s",i,buff);
break;
}
}
}
break;
case 'c':
while(read(fh,&c,1))
{
buff[j++]=c;
if(c=='\n')
{
buff[j]='\0';
j=0;
p=buff;
while(p=strstr(p,pattern))
{
count++;
p++;
}
}
}
printf("total no of occurances=%d\n",count);
break;
case 'a':
while(read(fh,&c,1))
{
buff[j++]=c;
if(c=='\n')
{
buff[j]='\0';
j=0;
i++;
if(strstr(buff,pattern))
printf("%d: %s",i,buff);

}
}
}//switch
close(fh);


}//search
//}
int main()
{
char buff[80],*args[10];//search F pettern fname
int pid;
while(1)
{
printf("myshell$");
fflush(stdin);
fgets(buff,80,stdin);
buff[strlen(buff)-1]='\0';
make_toks(buff,args);
if(strcmp(args[0],"search")==0)//search f pattern fname
search(args[3],args[1][0],args[2]);
else
{
pid = fork();
if(pid>0)
wait();
else
{
if(execvp(args[0],args)==-1)
printf("bad command \n");
}
}
}
return 0;
}

#include <stdio.h>


void swap(int *a,int *b)
{
int temp=*a;
*a=*b;
*b=temp;
}
int main()
{
int n;
printf("Enter Number of Processes: ");
scanf("%d",&n);


int b[n],p[n],index[n];
for(int i=0;i<n;i++)
{
printf("Enter Burst Time and Priority Value for Process %d: ",i+1);
scanf("%d %d",&b[i],&p[i]);
index[i]=i+1;
}
for(int i=0;i<n;i++)
{
int a=p[i],m=i;

//Finding out highest priority element and placing it at its desired position
for(int j=i;j<n;j++)
{
if(p[j] > a)
{
a=p[j];
m=j;
}
}

//Swapping processes
swap(&p[i], &p[m]);
swap(&b[i], &b[m]);
swap(&index[i],&index[m]);
}


int t=0;

//Printing scheduled process
printf("Order of process Execution is\n");
for(int i=0;i<n;i++)
{
printf("P%d is executed from %d to %d\n",index[i],t,t+b[i]);
t+=b[i];
}
printf("\n");
printf("Process Id Burst Time Wait Time TurnAround Time\n");
int wait_time=0;
for(int i=0;i<n;i++)
{
printf("P%d %d %d %d\n",index[i],b[i],wait_time,wait_time + b[i]);
wait_time += b[i];
}
return 0;
}