C-Program of Disk scheduling Algorithms in operating system (OS).

What is disk scheduling:-

Disk scheduling is schedule I/O requests arriving for the disk. It is important because:-

Multiple I/O requests may arrive by different processes and only one I/O request can be served at a time by the disk controller. Thus other I/O requests need to wait in the waiting queue and need to be scheduled.
Two or more request may be far from each other so can result in greater disk head movement.
Hard drives are one of the slowest parts of the computer system and thus need to be accessed in an efficient manner.

There are some important point in Disk scheduling:-

Seek Time: Seek time is the time taken to locate the disk head to a specified track where the data is to be read or write. So the disk scheduling algorithm that gives minimum average seek time is better.
Rotational Latency: Rotational Latency is the time taken by the desired sector of disk to rotate into a position so that it can access the read/write heads. So the disk scheduling algorithm that gives minimum rotational latency is better.
Transfer Time: Transfer time is the time to transfer the data. It depends on the rotating speed of the disk and number of bytes to be transferred.
Disk Access Time: Disk Access Time is=( Seek+ Rotational+ transfer time)

There are some Disk scheduling algorithms:-

1) FCFS (First come first serve)

2) SSTF (Short seek time first) :- C C++ Python

3) Scan/ Elevator Disk scheduling

4) C-scan disk scheduling

5) Look disk scheduling

6) C-look disk scheduling

You can simply click on the link and can find the program of the scheduling algorithms.

codechef problems:-

Wipro :-

Infytq :-

Key Points;-

Hackerrank:-

C-tutorial:-

See more:-

6 Comments

Anonymous00:08
linked list program

#include
#include
#include
#define MAX 200

typedef struct dir
{
char fname[20];
int start;
struct dir *next;
}NODE;

NODE *first,*last;

int n,fb,bit[MAX];

void init()
{
int i;

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

fb = n;

for(i=0;i<10;i++)
{
int k = rand()%n;
if(bit[k]!=-2)
{
bit[k]=-2;
fb--;
}
}
}

void show_bitvector()
{
int i;
for(i=0;ifname);
i = p->start;
while(i!=-1)
{
printf("%d->",i);
i=bit[i];
}
printf("NULL\n");

p=p->next;
}
}

void create()
{
NODE *p;
char fname[20];
int i,j,nob;

printf("Enter file name:");
scanf("%s",fname);

printf("Enter no.of blocks:");
scanf("%d",&nob);

if(nob>fb)
{
printf("Failed to create file %s\n",fname);
return;
}

for(i=0;ifname,fname);
p->start=i;
p->next=NULL;

if(first==NULL)
first=p;
else
last->next=p;

last=p;

fb-=nob;

j=i+1;
nob--;

while(nob>0)
{
if(bit[j]==0)
{
bit[i]=j;
i=j;
nob--;
}
j++;
}

bit[i]=-1;
printf("File %s created successully.\n",fname);
}

void delete()
{
char fname[20];
NODE *p,*q;
int nob=0,i,j;

printf("Enter file name to be deleted:");
scanf("%s",fname);

p = q = first;
while(p!=NULL)
{
if(strcmp(p->fname,fname)==0)
break;

q=p;
p=p->next;
}

if(p==NULL)
{
printf("File %s not found.\n",fname);
return;
}

i = p->start;
while(i!=-1)
{
nob++;
j = i;
i = bit[i];
bit[j] = 0;
}

fb+=nob;

if(p==first)
first=first->next;
else if(p==last)
{
last=q;
last->next=NULL;
}
else
q->next = p->next;

free(p);

printf("File %s deleted successfully.\n",fname);
}

int main()
{
int ch;

init();

while(1)
{
printf("1.Show bit vector\n");
printf("2.Create new file\n");
printf("3.Show directory\n");
printf("4.Delete file\n");
printf("5.Exit\n");
printf("Enter your choice (1-5):");
scanf("%d",&ch);

switch(ch)
{
case 1:
show_bitvector();
break;
case 2:
create();
break;
case 3:
show_dir();
break;
case 4:
delete();
break;
case 5:
exit(0);
}
}

return 0;
}
arnav pawar00:10

bro plz dont delete this

os indexed file

#include
main()
{
int n,m[20],i,j,sb[20],s[20],b[20][20],x;
printf("Enter no. of files:");
scanf("%d",&n);
for(i=0;i<n;i++)
{ printf("Enter starting block and size of file%d:",i+1);
scanf("%d%d",&sb[i],&s[i]);
printf("Enter blocks occupied by file%d:",i+1);
scanf("%d",&m[i]);
printf("enter blocks of file%d:",i+1);
for(j=0;j<m[i];j++)
scanf("%d",&b[i][j]);
} printf("\nFile\t index\tlength\n");
for(i=0;i<n;i++)
{
printf("%d\t%d\t%d\n",i+1,sb[i],m[i]);
}printf("\nEnter file name:");
scanf("%d",&x);
printf("file name is:%d\n",x);
i=x-1;
printf("Index is:%d",sb[i]);
printf("Block occupied are:");
for(j=0;j<m[i];j++)
printf("%3d",b[i][j]);

}
arnav00:10

banker program

#include

#include

void print(int x[][10],int n,int m)
{

int i,j;

for(i=0;i N[pid][i]){

printf("\n Error encountered.\n");

exit(0);

}

for(i=0;i AV[0][i]){

printf("\n Resources unavailable.\n");

exit(0);

}

for(i=0;i W[0][j])

flag=1;

}

if(flag == 0 && F[i] == 0){

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

W[0][j]+=A[i][j];

F[i]=1;

pflag++;

a[x++]=i;

}

}

}

if(pflag == n)

return 1;

}

return 0;

}

//Banker's Algorithm

void accept(int A[][10],int N[][10],int M[10][10],int W[1][10],int *n,int *m){

int i,j;

printf("\n Enter total no. of processes : ");

scanf("%d",n);

printf("\n Enter total no. of resources : ");

scanf("%d",m);

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

printf("\n Process %d\n",i+1);

for(j=0;j<*m;j++){

printf(" Allocation for resource %d : ",j+1);

scanf("%d",&A[i][j]);

printf(" Maximum for resource %d : ",j+1);

scanf("%d",&M[i][j]);

}

}

printf("\n Available resources : \n");

for(i=0;i<*m;i++){

printf(" Resource %d : ",i+1);

scanf("%d",&W[0][i]);

}

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

for(j=0;j<*m;j++)

N[i][j]=M[i][j]-A[i][j];

printf("\n Allocation Matrix");

print(A,*n,*m);

printf("\n Maximum Requirement Matrix");

print(M,*n,*m);

printf("\n Need Matrix");

print(N,*n,*m);

}

int banker(int A[][10],int N[][10],int W[1][10],int n,int m){

int j,i,a[10];

j=safety(A,N,W,n,m,a);

if(j != 0 ){

printf("\n\n");

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

printf(" P%d ",a[i]);

printf("\n A safety sequence has been detected.\n");

return 1;

}else{

printf("\n Deadlock has occured.\n");

return 0;

}

}

int main(){

int ret;

int A[10][10];

int M[10][10];

int N[10][10];

int W[1][10];

int n,m,pid,ch;

printf("\n DEADLOCK AVOIDANCE USING BANKER'S ALGORITHM\n");

accept(A,N,M,W,&n,&m);

ret=banker(A,N,W,n,m);

if(ret !=0 ){

printf("\n Do you want make an additional request ? (1=Yes|0=No)");

scanf("%d",&ch);

if(ch == 1){

printf("\n Enter process no. : ");

scanf("%d",&pid);

res_request(A,N,W,pid-1,m);

ret=banker(A,N,W,n,m);

if(ret == 0 )

exit(0);

}

}else

exit(0);

return 0;

}
arnav00:12

HELLO WORLD MPI:

#include
#include

int main(int argc, char** argv) {
// Initialize the MPI environment
MPI_Init(NULL, NULL);

// Get the number of processes
int world_size;
MPI_Comm_size(MPI_COMM_WORLD, &world_size);

// Get the rank of the process
int world_rank;
MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);

// Get the name of the processor
char processor_name[MPI_MAX_PROCESSOR_NAME];
int name_len;
MPI_Get_processor_name(processor_name, &name_len);

// Print off a hello world message
printf("Hello world from processor %s, rank %d out of %d processors\n",
processor_name, world_rank, world_size);

// Finalize the MPI environment.
MPI_Finalize();
}
arnav00:13
ass1bankers algorithm

#include
#define MAX 10

int m,n,total[MAX],avail[MAX],alloc[MAX][MAX],
max[MAX][MAX],need[MAX][MAX],work[MAX],finish[MAX],
seq[MAX],request[MAX];

void accept()
{
int i,j;

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

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

printf("Enter total no.of resources of each resource type:\n");

for(i=0;iwork[j])
break;
}

if(j==m) return i;
}

i=(i+1)%n;
}while(i!=s);

return -1;
}

void banker()
{
int i,j,k=0;

for(i=0;ineed[pno][j])
break;
}

if(j==m)
{
for(j=0;javail[j])
break;
}

if(j==m)
{
for(j=0;j<m;j++)
{
avail[j]-=request[j];
alloc[pno][j]+=request[j];
need[pno][j]-=request[j];
print();
banker();
}
}
else
printf("Process P%d must wait.\n",pno);
}
else
printf("Process P%d has exceeded its maximum claim\n",pno);

return 0;
}
Anonymous00:20
sequencial

#include
#include
#include
#define MAX 200

typedef struct dir
{
char fname[20];
int start;
struct dir *next;
}NODE;

NODE *first,*last;

int n,fb,bit[MAX];

void init()
{
int i;

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

fb = n;

for(i=0;i<10;i++)
{
int k = rand()%n;
if(bit[k]!=-2)
{
bit[k]=-2;
fb--;
}
}
}

void show_bitvector()
{
int i;
for(i=0;ifname);
i = p->start;
while(i!=-1)
{
printf("%d->",i);
i=bit[i];
}
printf("NULL\n");

p=p->next;
}
}

void create()
{
NODE *p;
char fname[20];
int i,j,nob;

printf("Enter file name:");
scanf("%s",fname);

printf("Enter no.of blocks:");
scanf("%d",&nob);

if(nob>fb)
{
printf("Failed to create file %s\n",fname);
return;
}

for(i=0;ifname,fname);
p->start=i;
p->next=NULL;

if(first==NULL)
first=p;
else
last->next=p;

last=p;

fb-=nob;

j=i+1;
nob--;

while(nob>0)
{
if(bit[j]==0)
{
bit[i]=j;
i=j;
nob--;
}
j++;
}

bit[i]=-1;
printf("File %s created successully.\n",fname);
}

void delete()
{
char fname[20];
NODE *p,*q;
int nob=0,i,j;

printf("Enter file name to be deleted:");
scanf("%s",fname);

p = q = first;
while(p!=NULL)
{
if(strcmp(p->fname,fname)==0)
break;

q=p;
p=p->next;
}

if(p==NULL)
{
printf("File %s not found.\n",fname);
return;
}

i = p->start;
while(i!=-1)
{
nob++;
j = i;
i = bit[i];
bit[j] = 0;
}

fb+=nob;

if(p==first)
first=first->next;
else if(p==last)
{
last=q;
last->next=NULL;
}
else
q->next = p->next;

free(p);

printf("File %s deleted successfully.\n",fname);
}

int main()
{
int ch;

init();

while(1)
{
printf("1.Show bit vector\n");
printf("2.Create new file\n");
printf("3.Show directory\n");
printf("4.Delete file\n");
printf("5.Exit\n");
printf("Enter your choice (1-5):");
scanf("%d",&ch);

switch(ch)
{
case 1:
show_bitvector();
break;
case 2:
create();
break;
case 3:
show_dir();
break;
case 4:
delete();
break;
case 5:
exit(0);
}
}

return 0;
}

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