X to the power of Y using recursion in C ++

                                           

#include<iostream.h>

float powerec(float b, float r)
{
 if(r==0)
  return 1;
 else
  return(b*powerec(b,r-1));
}

void main()
{
 float b,r;
 b=0; r=0;
 cout<<"\nEnter The Base: ";
 cin>>b;
 cout<<"\nEnter The Power: ";
 cin>>r;
 float res=powerec(b,r);
 cout<<"\nThe Result Is: "<<res;
}

Binary Search Tree Program in C++

#include <iostream.h>
#include <process.h>

class tnode
{
public:
 int data;
 tnode *lchild;
 tnode *rchild;
 tnode(int n,tnode *l=0,tnode *r=0)
 {  
  data=n;
  lchild=l;
  rchild=r;
 }
};

class Queue
{
private:
    int front,rear,size;
 tnode **a;
public:
 Queue(int size=0)
 {
  front=rear=-1;
  if (size!=0)
   a=new tnode*[size];
  else
   a=0;
  this->size=size;
 }
 void enqueue(tnode* el);
 tnode* dequeue();
 bool isempty() const;
};

void Queue::enqueue(tnode* el)
{
 if(isempty())
 {
       front=rear=0;
    a[front]=el;
 }
 else
 {
  rear=(rear+1)%size;
  a[rear]=el;
 }
}
tnode* Queue::dequeue()
{
 tnode* i;
 if (front==-1)
  cout<<"Empty list. Deletion not possible";
 else if (front==rear)
 {
  i=a[front];
     front=rear=-1;
 }
 else
 {  
  i=a[front];
  front=(front+1)%size;
 }
    return i;
}

bool Queue::isempty() const
{
 return(front==-1);
}

class BST
{
private:
 tnode *root;
 void preorder(tnode *);
 void postorder(tnode *);
 void inorder(tnode *);
public:
 BST()
 {
  root=0;
 }

 void insert(int x);
 void insert(tnode* &p,int x);
 void delete_by_copying(int x);
 void delete_by_merging(int x);
 tnode* search(int x);
 tnode* search(tnode * p,int x);
 void preorder();
 void postorder();
 void inorder();
 void level_by_level_traversal();
 int count_leafnode();
 int count_leafnode(tnode *t);
 int count_nonleaf();
 int count_nonleaf(tnode *t);
 int height();
 int height(tnode *t);
 tnode* mirror();
 tnode* mirror(tnode *p);
};

// Inserting an element
void BST::insert(int x)
{
 treenode*t=new treenode(x);
 if(root==NULL)
 {
  root=t;
  return;
 }
 treenode*p,*fp;
 p=root;
 fp=0;
 while(p!=0)
 {
  fp=p;
  if(x==p->data)
   throw"DUPLICATE VALUE";
  else if(x<p->data)
   p=p->lchild;
  else
   p=p->rchild;
 }
 if(x<fp->data)
  fp->lchild=t;
 else
  fp->rchild=t;
}

// Deletion By Copying
void BST::delete_by_copying(int x)
{
 if (root==0)
  throw "Empty tree";
 tnode *p=root;
 tnode *fp=0;
 while(p!=0 && p->data!=x)
 {
  fp=p;
  if (x<p->data)
   p=p->lchild;
  else
   p=p->rchild;
 }
    if (p==0)
  throw "Element not present ";
 bool lchild;
 if (fp!=0)
   lchild=(x<fp->data)?true:false;
 // if deleted node is a leaf
 if ((p->lchild==0) && (p->rchild)==0)
 {
  if (fp==0)
  {
   root=0;return;
  }
  if (lchild)
   fp->lchild=0;
     else
     fp->rchild=0;
 }
 // if deleted node has lchild only
 else if (p->rchild==0)
 {  
  if (fp==0)
  {
   root=p->lchild;
   return;
  }
  if (lchild)
   fp->lchild=p->lchild;
     else
     fp->rchild=p->lchild;
 }
 // if deleted node has rchild only
 else if (p->lchild==0)
 {  
  if (fp==0)
  {
   root=p->rchild;
   return;
  }
  if (lchild)
   fp->lchild=p->rchild;
     else
      fp->rchild=p->rchild;
 }
 // if both the children exists
 else
 { tnode *q=p->rchild;
   tnode *fq=p;
   while (q->lchild!=0)
   {
    fq=q;
    q=q->lchild;
   }
      p->data=q->data;
      if (q->data<fq->data)
    fq->lchild=q->rchild;
   else
    fq->rchild =q->rchild;
   delete q;
 }
}

// Deletion by Merging
void BST::delete_by_merging(int x)
{
 if (root==0)
  throw "Empty tree";
 tnode *p=root;
 tnode *fp=0;
 while(p!=0 && p->data!=x)
 {
  fp=p;
  if (x<p->data)
   p=p->lchild;
  else
   p=p->rchild;
 }
    if (p==0)
  throw "Element not present ";
 bool lchild;
 if (fp!=0)
   lchild=(x<fp->data)?true:false;
 // if deleted node is a leaf
 if ((p->lchild==0) && (p->rchild)==0)
 {
  if (fp==0)
  {
   root=0;return;
  }
  if (lchild)
   fp->lchild=0;
     else
      fp->rchild=0;
 }
 // if deleted node has lchild only
 else if (p->rchild==0)
 {  
  if (fp==0)
  {
   root=p->lchild;
   return;
  }
  if (lchild)
   fp->lchild=p->lchild;
     else
      fp->rchild=p->lchild;
 }
 // if deleted node has rchild only
 else if (p->lchild==0)
 {
  if (fp==0)
  {
   root=p->rchild;
   return;
  }
  if (lchild)
   fp->lchild=p->rchild;
     else
      fp->rchild=p->rchild;
 }
 // if both the children exists
 else
 {
   tnode *q=p->lchild;
   tnode *rc=p->rchild;
   while (q->rchild!=0)
   {
    q=q->rchild;
   }
   q->rchild=rc;
      if (fp==0)
    root=p->lchild;
   else
   {  
    if (p->data<fp->data)
     fp->lchild=p->lchild;
    else
     fp->rchild=p->lchild;
   }
   delete p;
 }
 }

//Searching an element
tnode* BST::search(int x)
{
          if (root==0)
     return(0);
          if (root->data==x)
     return (root);
          if (x<root->data)
     return(search(root->lchild,x));
          else
     return(search(root->rchild,x));
}

tnode* BST::search(tnode * p,int x)
{
          if (p==0)
     return(0);
          if (p->data==x)
     return (p);
          if (x<p->data)
     return(search(p->lchild,x));
          else
     return(search(p->rchild,x));
}

// Inorder Traversal
void BST::inorder()
{
 if (root==0)
  return;
 inorder(root->lchild);
 cout<<root->data<<"  ";
 inorder(root->rchild);
}

void BST::inorder(tnode* r)
{
 if (r==0)
  return;
 inorder(r->lchild);
 cout<<r->data<<"  ";
 inorder(r->rchild);
}

// Preorder Traversal
void BST::preorder()
{
 if (root==0)
  return;
 cout<<root->data<<"  ";
 preorder(root->lchild);
 preorder(root->rchild);
}

void BST::preorder(tnode* r)
{
 if (r==0)
  return;
 cout<<r->data<<"  ";
 preorder(r->lchild);
 preorder(r->rchild);
}

//Postorder Traversal
void BST::postorder()
{
 if (root==0)
  return;
 postorder(root->lchild);
 postorder(root->rchild); 
 cout<<root->data<<"  ";
}

void BST::postorder(tnode* r)
{
 if (r==0)
  return;
 postorder(r->lchild);
 postorder(r->rchild);
 cout<<r->data<<"  ";
}

// Level by Level Traversal
void BST::level_by_level_traversal()
{
 if(root==0)
 {
  cout<<"Empty tree";
  return;
 }
 cout<<"\nLevel by level traversal is ";
 Queue q(10);
 q.enqueue(root);
 while(!q.isempty())
 {
  tnode *p=q.dequeue();
  cout<<p->data<<" ";
  if(p->lchild!=0)
   q.enqueue(p->lchild);
  if(p->rchild!=0)
   q.enqueue(p->rchild);
 }
}

//Count leaf nodes
int BST::count_leafnode()
{
 if(root==0)
  return 0;
 else if(root->lchild==0&&root->rchild==0)
  return 1;
 else
  return(count_leafnode(root->lchild)+count_leafnode(root->rchild));
}

int BST::count_leafnode(tnode *t)
{
 if(t==0)
  return 0;
 else if(t->lchild==0&&t->rchild==0)
  return 1;
 else
  return(count_leafnode(t->lchild)+count_leafnode(t->rchild));
}

//Count non leaf nodes
int BST::count_nonleaf()
{
 if(root==0)
  return 0;
 else if(root->lchild==0&&root->rchild==0)
  return 0;
 else
  return(1+count_nonleaf(root->lchild)+count_nonleaf(root->rchild));
}  

int BST::count_nonleaf(tnode *t)
{
 if(t==0)
  return 0;
 else if(t->lchild==0&&t->rchild==0)
  return 0;
 else
  return(1+count_nonleaf(t->lchild)+count_nonleaf(t->rchild));
}

//Calculate height of tree
int BST::height()
{
 if (root==0)
  return 0;
 else if (root->lchild==0 && root->rchild==0)
  return 1;
 else
 {
   int hl=height(root->lchild);
   int hr=height(root->rchild);
   int max=hl>hr?hl:hr;
   return(max+1);
 }
}

int BST::height(tnode *t)
{
 if(t==0)
  return 0;
 else if(t->lchild==0&&t->rchild==0)
  return 1;
 else
 {
  int x=height(t->lchild);
  int y=height(t->rchild);
  if(x>y)
   return(1+x);
  else
   return (1+y);
 }
}

//Mirror image of tree
tnode* BST::mirror()
{
 if(root == NULL)
  return root ;
 else
 {
  mirror(root->lchild);
  mirror(root->rchild);
  tnode *temp;
  temp=root->lchild;
  root->lchild=root->rchild;
  root->rchild=temp;
 }
 return root;
}
tnode* BST::mirror(tnode *p)
{
 if(p == NULL)
  return p ;
 else
 {
  mirror(p->lchild);
  mirror(p->rchild);
  tnode *temp;
  temp=p->lchild;
  p->lchild=p->rchild;
  p->rchild=temp;
 }
 return p;
}

void main()
{
 BST b;
 int i,n;
 tnode *p;
 int ch;
 do
 {
  cout<<"\n\nMAIN MENU";
  cout<<"\n1.)Insertion ";
  cout<<"\n2.)Deletion by copying ";
  cout<<"\n3.)Deletion by merging";
  cout<<"\n4.)Search a no in BST ";
  cout<<"\n5.)In-Order Traversal ";
  cout<<"\n6.)Pre-Order Traversal ";
  cout<<"\n7.)Post-Order Traversal ";
  cout<<"\n8.)Level-by-level Traversal ";
  cout<<"\n9.)Count no of non leaf nodes ";
  cout<<"\n10.)Count no of leaf nodes ";
  cout<<"\n11.)Height of tree ";
  cout<<"\n12.)Mirror image ";
  cout<<"\n13.)Exit ";
  cout<<"\n\n\t\t\t Enter your choice: ";
  cin>>ch;
  switch(ch)
  {
   case 1 : cout<<"\n Enter the node to be inserted : ";
     cin>>n;
     b.insert(n);
     cout<<"\n The tree in inorder traversal is: ";
     b.inorder();
     break;
   case 2 : cout<<"\n Enter the node to be deleted : ";
     cin>>n;
     b.delete_by_copying(n);
     cout<<"\n The tree in inorder traversal is: ";
     b.inorder();
     break;
                        case 3 : cout<<"\n Enter the node to be deleted : ";
     cin>>n;
     b.delete_by_merging(n);
     cout<<"\n The tree in inorder traversal is: ";
     b.inorder();
     break;
   case 4 : cout<<"\n Enter the node to be searched: ";
            cin>>n;
     p=b.search(n);
     if(p!=0)
       cout<<"\n Node "<<p<<" found";
     else
       cout<<"\n Node not present";
     break;
   case 5 : cout<<"\n Inorder traversal is: ";
            b.inorder();
     break;
   case 6 : cout<<"\n Preorder traversal is: ";
            b.preorder();
     break;
   case 7 : cout<<"\n Postorder traversal is: ";
            b.postorder();
     break;
   case 8 : b.level_by_level_traversal();
     break;
          case 9 : n=b.count_nonleaf();
     cout<<"No. of non leaf nodes= "<<n;
            break;
          case 10: n=b.count_leafnode();
     cout<<"No. of leaf nodes= "<<n;
            break;
   case 11: n=b.height();
     cout<<"Height of tree= "<<n;
     break;
   case 12: p=b.mirror();
     cout<<"\n The tree in inorder traversal is: ";
     b.inorder();
     break;
   default: exit(0);
  }
 }while(ch!=13);
}

STOP AND WAIT PROTOCOL PROGRAM IN C++

#include <conio.h>
#include <dos.h>
#include <stdio.h>
#include <stdlib.h>

#define TIMEOUT 5
#define MAX_SEQ 1
#define TOT_PACKETS 8
#define inc(k) if(k<MAX_SEQ) k++; else k=0;
typedef struct
{
 int data;
}packet;
typedef struct
{
 int kind;
 int seq;
 int ack;
 packet info;
 int err;
}frame;
frame DATA;
typedef enum{frame_arrival,err,timeout,no_event} event_type;

void from_network_layer(packet *);
void to_network_layer(packet *);
void to_physical_layer(frame *);
void from_physical_layer(frame *);
void wait_for_event_sender(event_type *);
void wait_for_event_reciever(event_type *);
void reciever();
void sender();

int i=1;         //Data to be sent by sender
char turn;      //r , s
int DISCONNECT=0;
/*__________________________________________________________________________*/
void main()
{
 clrscr();
 randomize();
 while(!DISCONNECT)
 {
   sender();
   delay(400);
   reciever();
 }
 getch();
}
/*__________________________________________________________________________*/
void sender()
{
 static int frame_to_send=0;
 static frame s;
 packet buffer;
 event_type event;
 static int flag=0;

 if(flag==0)
 {
  from_network_layer(&buffer);
  s.info = buffer;
  s.seq = frame_to_send;
  printf("SENDER :  Info = %d    Seq No = %d     ",s.info,s.seq);
  turn = 'r';
  to_physical_layer(&s);
  flag = 1;
 }
 wait_for_event_sender(&event);
 if(turn=='s')
  {
   if(event==frame_arrival)
    {
      from_network_layer(&buffer);
      inc(frame_to_send);
      s.info = buffer;
      s.seq = frame_to_send;
      printf("SENDER :  Info = %d    Seq No = %d     ",s.info,s.seq);
      turn = 'r';
      to_physical_layer(&s);
    }
   if(event==timeout)
    {
      printf("SENDER : Resending Frame             ");
      turn = 'r';
      to_physical_layer(&s);
    }
  }
}
/*__________________________________________________________________________*/
void reciever()
{
 static int frame_expected=0;
 frame r,s;
 event_type event;

 wait_for_event_reciever(&event);
 if(turn=='r')
  {
   if(event==frame_arrival)
    {
     from_physical_layer(&r);
     if(r.seq==frame_expected)
      {
       to_network_layer(&r.info);
       inc(frame_expected);
      }
     else
       printf("RECIEVER : Acknowledgement Resent\n");

     turn = 's';
     to_physical_layer(&s);
    }
   if(event==err)
    {
      printf("RECIEVER : Garbled Frame\n");
      turn = 's';     //if frame not recieved
    }                 //sender shold send it again
  }
}
/*__________________________________________________________________________*/
void from_network_layer(packet *buffer)
{
   (*buffer).data = i;
   i++;
}
/*___________________________________________________________________________*/
void to_physical_layer(frame *s)
{                     // 0 means error
 s->err = random(4);  //non zero means no error
 DATA = *s;           //probability of error = 1/4
}
/*___________________________________________________________________________*/
void to_network_layer(packet *buffer)
{
 printf("RECIEVER :Packet %d recieved , Ack Sent\n",(*buffer).data);
 if(i>TOT_PACKETS)          //if all packets recieved then disconnect
  {
   DISCONNECT = 1;
   printf("\nDISCONNECTED");
  }
}
/*___________________________________________________________________________*/
void from_physical_layer(frame *buffer)
{
 *buffer = DATA;
}
/*___________________________________________________________________________*/
void wait_for_event_sender(event_type * e)
{
 static int timer=0;

 if(turn=='s')
  {
   timer++;
   if(timer==TIMEOUT)
    {
     *e = timeout;
     printf("SENDER : Ack not recieved=> TIMEOUT\n");
     timer = 0;
     return;
    }
   if(DATA.err==0)
     *e = err;
   else
    {
     timer = 0;
     *e = frame_arrival;
    }
  }
}
/*____________________________________________________________________________*/
void wait_for_event_reciever(event_type * e)
{
 if(turn=='r')
  {
   if(DATA.err==0)
     *e = err;
   else
     *e = frame_arrival;
  }
}

/*    OUTPUT

SENDER :  Info = 1    Seq No = 0     RECIEVER :Packet 1 recieved , Ack Sent
SENDER : Ack not recieved=> TIMEOUT
SENDER : Resending Frame             RECIEVER : Acknowledgement Resent
SENDER :  Info = 2    Seq No = 1     RECIEVER :Packet 2 recieved , Ack Sent
SENDER :  Info = 3    Seq No = 0     RECIEVER :Packet 3 recieved , Ack Sent
SENDER : Ack not recieved=> TIMEOUT
SENDER : Resending Frame             RECIEVER : Acknowledgement Resent
SENDER :  Info = 4    Seq No = 1     RECIEVER :Packet 4 recieved , Ack Sent
SENDER :  Info = 5    Seq No = 0     RECIEVER :Packet 5 recieved , Ack Sent
SENDER :  Info = 6    Seq No = 1     RECIEVER :Packet 6 recieved , Ack Sent
SENDER :  Info = 7    Seq No = 0     RECIEVER :Packet 7 recieved , Ack Sent
SENDER :  Info = 8    Seq No = 1     RECIEVER : Garbled Frame
SENDER : Ack not recieved=> TIMEOUT
SENDER : Resending Frame             RECIEVER :Packet 8 recieved , Ack Sent

DISCONNECTED
*/

SELECTIVE REPEAT PROTOCOL PROGRAM IN C++

// SIMULATE SELECTIVE REPEAT PROTOCOL

# include <iostream.h>
# include <conio.h>
# include <stdlib.h>
# include <time.h>
# include <math.h>

# define TOT_FRAMES 500
# define FRAMES_SEND 10

class sel_repeat
{
 private:
  int fr_send_at_instance;
  int arr[TOT_FRAMES];
  int send[FRAMES_SEND];
  int rcvd[FRAMES_SEND];
  char rcvd_ack[FRAMES_SEND];
  int sw;
  int rw; // tells expected frame
 public:
  void input();
  void sender(int);
  void reciever(int);
};

void sel_repeat :: input()
{
 int n;  // no of bits for the frame
 int m;  // no of frames from n bits

 cout << "Enter the no of bits for the sequence number ";
 cin >> n;

 m = pow (2 , n);

 int t = 0;

 fr_send_at_instance = (m / 2);

 for (int i = 0 ; i < TOT_FRAMES ; i++)
 {
  arr[i] = t;
  t = (t + 1) % m;
 }

 for (i = 0 ; i < fr_send_at_instance ; i++)
 {
  send[i] = arr[i];
  rcvd[i] = arr[i];
  rcvd_ack[i] = 'n';
 }

 rw = sw = fr_send_at_instance;

 sender(m);
}

void sel_repeat :: sender(int m)
{
 for (int i = 0 ; i < fr_send_at_instance ; i++)
 {
  if ( rcvd_ack[i] == 'n' )
   cout << " SENDER   : Frame " << send[i] << " is sent\n";
 }
 reciever (m);
}

void sel_repeat :: reciever(int m)
{
 time_t t;
 int f;
 int f1;
 int a1;
 char ch;

 srand((unsigned) time(&t));

 for (int i = 0 ; i < fr_send_at_instance ; i++)
 {
  if (rcvd_ack[i] == 'n')
  {
   f = rand() % 10;

   // if = 5 frame is discarded for some reason
   // else frame is correctly recieved

   if (f != 5)
   {
    for (int j = 0 ; j < fr_send_at_instance ; j++)

     if (rcvd[j] == send[i])
     {
      cout << "RECIEVER : Frame " << rcvd[j] << " recieved correctly\n";
      rcvd[j] = arr[rw];
      rw = (rw + 1) % m;
      break;
     }

    if (j == fr_send_at_instance)
     cout << "RECIEVER : Duplicate frame " << send[i] << " discarded\n";

    a1 = rand() % 5;

     // if a1 == 3 then ack is lost
     //            else recieved

    if (a1 == 3)
    {
     cout << "(Acknowledgement " << send[i] << " lost)\n";
     cout << " (SENDER TIMEOUTS --> RESEND THE FRAME)\n";
     rcvd_ack[i] = 'n';
    }
    else
    {
     cout << "(Acknowledgement " << send[i] << " recieved)\n";
     rcvd_ack[i] = 'p';
    }
   }
   else
   {
    int ld = rand() % 2;

    // if = 0 then frame damaged
    // else frame lost

    if (ld == 0)
    {
     cout << "RECIEVER : Frame " << send[i] << " is damaged\n";
     cout << "RECIEVER : Negative acknowledgement " << send[i]  << " sent\n";
    }
    else
    {
     cout << "RECIEVER : Frame " << send[i] << " is lost\n";
     cout << " (SENDER TIMEOUTS --> RESEND THE FRAME)\n";
    }
    rcvd_ack[i] = 'n';
   }
  }
 }

 for ( int j = 0 ; j < fr_send_at_instance ; j++)
 {
  if (rcvd_ack[j] == 'n')
   break;
 }

 i = 0 ;

 for (int k = j ; k < fr_send_at_instance ; k++)
 {
  send[i] = send[k];

  if (rcvd_ack[k] == 'n')
   rcvd_ack[i] = 'n';
  else
   rcvd_ack[i] = 'p';

  i++;
 }

 if ( i != fr_send_at_instance )
 {
  for ( int k = i ; k < fr_send_at_instance ; k++)
  {
   send[k] = arr[sw];
   sw = (sw + 1) % m;
   rcvd_ack[k] = 'n';
  }
 }
 cout << "Want to continue...";
 cin >> ch;
 cout << "\n";

 if (ch == 'y')
  sender(m);
 else
  exit(0);
}

void main()
{
 clrscr();
 sel_repeat sr;
 sr.input();
 getch();
}


/*              OUTPUT

Enter the no of bits for the sequence number 6
 SENDER   : Frame 24 is sent
 SENDER   : Frame 32 is sent
 SENDER   : Frame 32 is sent
 SENDER   : Frame 27 is sent
 SENDER   : Frame 28 is sent
 SENDER   : Frame 29 is sent
 SENDER   : Frame 30 is sent
 SENDER   : Frame 31 is sent
RECIEVER : Frame 24 is lost
 (SENDER TIMEOUTS --> RESEND THE FRAME)
RECIEVER : Frame 32 recieved correctly
(Acknowledgement 32 recieved)
RECIEVER : Frame 33 recieved correctly
(Acknowledgement 34 recieved)
RECIEVER : Frame 27 recieved correctly
(Acknowledgement 34 recieved)
RECIEVER : Frame 28 is damaged
RECIEVER : Negative acknowledgement 28 sent
RECIEVER : Frame 29 recieved correctly
(Acknowledgement 35 recieved)
RECIEVER : Frame 30 recieved correctly
(Acknowledgement 36 lost)
 (SENDER TIMEOUTS --> RESEND THE FRAME)
RECIEVER : Frame 31 recieved correctly
(Acknowledgement 37 recieved)
Want to continue...n

*/

GO BACK N PROTOCOL PROGRAM IN C++

# include <iostream.h>
# include <conio.h>
# include <stdlib.h>
# include <time.h>
# include <math.h>

# define TOT_FRAMES 500
# define FRAMES_SEND 10

class gobkn
{
 private:
  int fr_send_at_instance;
  int arr[TOT_FRAMES];
  int arr1[FRAMES_SEND];
  int sw;
  int rw; // tells expected frame
 public:
  gobkn();
  void input();
  void sender(int);
  void reciever(int);
};

gobkn :: gobkn()
{
 sw = 0;
 rw = 0;
}

void gobkn :: input()
{
 int n;  // no of bits for the frame
 int m;  // no of frames from n bits

 cout << "Enter the no of bits for the sequence no ";
 cin >> n;

 m = pow (2 , n);

 int t = 0;

 fr_send_at_instance = (m / 2);

 for (int i = 0 ; i < TOT_FRAMES ; i++)
 {
  arr[i] = t;
  t = (t + 1) % m;
 }

 sender(m);
}

void gobkn :: sender(int m)
{
 int j = 0;

 for (int i = sw ; i < sw + fr_send_at_instance ; i++)
 {
  arr1[j] = arr[i];
  j++;
 }

 for (i = 0 ; i < j ; i++)
  cout << " SENDER   : Frame " << arr1[i] << " is sent\n";

 reciever (m);
}

void gobkn :: reciever(int m)
{
 time_t t;
 int f;
 int f1;
 int a1;
 char ch;

 srand((unsigned) time(&t));
 f = rand() % 10;

   // if = 5 frame is discarded for some reason
   // else they are correctly recieved

 if (f != 5)
 {
  for (int i = 0 ; i < fr_send_at_instance ; i++)
  {
   if (rw == arr1[i])
   {
    cout << "RECIEVER : Frame " << arr1[i] << " recieved correctly\n";
    rw = (rw + 1) % m;
   }
   else
    cout << "RECIEVER : Duplicate frame " << arr1[i] << " discarded\n";
  }
  a1 = rand() % 15;

   // if a1 belongs to 0 to 3 then
   //     all ack after this (incl this one) lost
   // else
   //     all recieved

  if (a1 >= 0 && a1 <= 3)
  {
   cout << "(Acknowledgement " << arr1[a1] << " & all after this lost)\n";
   sw = arr1[a1];
  }
  else
   sw = (sw + fr_send_at_instance) % m;
 }
 else
 {
  f1 = rand() % fr_send_at_instance;

   // f1 gives index of the frame being lost

  for (int i = 0 ; i < f1 ; i++)
  {
   if (rw == arr1[i])
   {
    cout << " RECIEVER : Frame " << arr1[i] << " recieved correctly\n";
    rw = (rw + 1) % m;
   }
   else
    cout << " RECIEVER : Duplicate frame " << arr1[i] << " discarded\n";
  }

  int ld = rand() % 2;
    // ld == 0 frame damaged
    // else frame lost
  if (ld == 0)
   cout << " RECIEVER : Frame " << arr1[f1] << " damaged\n";
  else
   cout << "            (Frame " << arr1[f1] << " lost)\n";

  for (i = f1 + 1 ; i < fr_send_at_instance ; i++)
    cout << " RECIEVER : Frame " << arr1[i] << " discarded\n";

  cout << " (SENDER TIMEOUTS --> RESEND THE FRAME)\n";

  sw = arr1[f1];
 }
 cout << "Want to continue...";
 cin >> ch;

 if (ch == 'y')
  sender(m);
 else
  exit(0);
}

void main()
{
 clrscr();
 gobkn gb;
 gb.input();
 getch();
}

/*   OUTPUT

Enter the no of bits for the sequence no 4
 SENDER   : Frame 0 is sent
 SENDER   : Frame 1 is sent
 SENDER   : Frame 2 is sent
 SENDER   : Frame 3 is sent
 SENDER   : Frame 4 is sent
 SENDER   : Frame 5 is sent
 SENDER   : Frame 6 is sent
 SENDER   : Frame 7 is sent
RECIEVER : Frame 0 recieved correctly
RECIEVER : Frame 1 recieved correctly
RECIEVER : Frame 2 recieved correctly
RECIEVER : Frame 3 recieved correctly
RECIEVER : Frame 4 recieved correctly
RECIEVER : Frame 5 recieved correctly
RECIEVER : Frame 6 recieved correctly
RECIEVER : Frame 7 recieved correctly
Want to continue...n

*/

DISTANCE VECTOR ROUTING PROGRAM IN C++

// SIMULATE DISTANCE VECTOR ROUTING
// ALWAYS DRY RUN FOR BETTER UNDERSTANDING

# include <iostream.h>
# include <conio.h>
# include <stdio.h>
# include <string.h>

class router
{
 private:
  char name[20];
  int dist[10];

 public:
  void get_r_table (int , int);
  friend void find_table (router *);
};

void find_table (router *);

int total_r;
int adj;
char names[10][20];
char N[20];

void router :: get_r_table (int no , int flag)
{
 if ( flag == 1 )
 {
  cout << "Enter the name of the adjacent router " << no << " : ";
  gets (name);
 }
 else
  strcpy (name , N);

 cout << "Enter the distances of each router from this router :\n";
 cout << "\tROUTER\tDISTANCE\n";
 cout << "\t------\t--------\n";

 for (int i = 0 ; i < total_r ; i++)
 {
  cout << "\t" << names[i] << "\t";
  if ( strcmp ( names[i] , name ) == 0 )
  {
   dist[i] = 0;
   cout << dist[i] << "\n";
  }
  else
   cin >> dist[i];
 }
}

void find_table(router *r)
{
 cout << "Routing table for router " << N << " :-\n";
 cout << "\tRouter\tDistance\n";
 cout << "\t------\t--------\n";

 for ( int i = 0 ; i < total_r ; i++ )
 {
  int temp;
  if ( strcmp (N , names[i] ) == 0 )
   temp = 0;
  else
  {
   temp = r[0].dist[i];
   for ( int j = 1 ; j < adj + 1 ; j++ )
    if ( r[j].dist[i] < temp && r[j].dist[i] != 0 )
     temp = r[j].dist[i] + r[0].dist[j];
  }
  r[0].dist[i] = temp;
 // r[0] contains data of the router whose routing table is to be found out
 }

 for ( i = 0 ; i < total_r ; i++ )
 {
  cout << "\t" << names[i] << "\t";
  cout << r[0].dist[i] << "\n";
 }
}

void main()
{
 router r[10];

 clrscr();

 cout << "Enter the total no of routers in the subnet [MAX 10] :- ";
 cin >> total_r;
 cout << "Enter the names of all the routers :-\n";
 for (int i = 0 ; i < total_r ; i++)
 {
  cout << "\t" << i + 1 << " . ";
  gets (names[i]);
 }
 cout << "Enter the router whose routing table is to be found out : ";
 gets (N);

 cout << "Enter the no of routers adjacent to this router : ";
 cin >> adj;

 int flag = 0;
 for ( i = 0 ; i < adj + 1; i++ )
 {
  r[i].get_r_table (i , flag);
  flag = 1;
 }

 find_table (r);
 getch();
}


/*                 OUTPUT


Enter the total no of routers in the subnet [MAX 10] :- 6
Enter the names of all the routers :-
        1 . A
        2 . B
        3 . C
        4 . D
        5 . E
        6 . F
Enter the router whose routing table is to be found out : C
Enter the no of routers adjacent to this router : 3
Enter the distances of each router from this router :
        ROUTER  DISTANCE
        ------  --------
        A       11
        B       6
        C       0
        D       3
        E       5
        F       6
Enter the name of the adjacent router 1 : B
Enter the distances of each router from this router :
        ROUTER  DISTANCE
        ------  --------
        A       5
        B       0
        C       8
        D       12
        E       6
        F       2
Enter the name of the adjacent router 2 : D
Enter the distances of each router from this router :
        ROUTER  DISTANCE
        ------  --------
        A       16
        B       12
        C       6
        D       0
        E       9
        F       10
Enter the name of the adjacent router 3 : E
Enter the distances of each router from this router :

        ROUTER  DISTANCE
        ------  --------
        A       7
        B       6
        C       3
        D       9
        E       0
        F       1
Routing table for router C :-
        Router  Distance
        ------  --------
        A       10
        B       6
        C       0
        D       3
        E       5
        F       4

*/

Cyclic Redundancy Check (CRC) Program in C++

// SIMULATE CYCLIC REDUNDANCY CHECK (CRC)
#include<iostream.h>
#include<conio.h>
#include<math.h>
#include<stdlib.h>
#include<graphics.h>
#include<DOS.h>
int digitinbin(int number)
{  int i=0;
  int n=number;
  while(n!=0)
    { n=n/2;
      i++;
    }
   return i;
}
int bintodec(int *a,int d)
{  int num=0;
   for(int i=0;i<d;i++)
    { if(a[i]==1)
       num=num+pow(2,i);
    }
  return num;
}
int* dectobin(int n)
{ int *A=new int[32];
  int i=0;
  int num=n;
  while(num!=0)
    { A[i]=num%2;
      num=num/2;
      i++;
    }
  return A;
}

int sender(int mess,int poly)
{ int k=0,num1;
  int d1=digitinbin(poly);
  mess=mess*pow(2,d1-1);
  int d2=digitinbin(mess);
  int *B=dectobin(mess);
  int counter=0;
  int times=d2-d1+1;
  int *temp=new int[d1];
  int a=pow(2,d1-1);
  while(counter<times)
   { int j=0;
     if(counter==0)
      {
     for(int i=times-counter-1;i<d2-counter;i++)
      {  temp[j]=B[i];
  j++;
      }
      num1=bintodec(temp,j);
      }
      int num2=poly;
      if(counter!=0)
       num1=k;
     if(num1>=a)
       k=num1^num2;
     else
       k=num1;

     if(d2-d1-counter-1>=0)
     {
     if(B[d2-d1-counter-1]==1)
      k=k*2+1;
     else
      k=k*2;
     }
   counter++;
    }
   return (k^mess);
}
void receiver(int mess,int poly)
{ int k=0,num1;
  int d1=digitinbin(poly);
  int d2=digitinbin(mess);
  int *B=dectobin(mess);
  int counter=0;
  int times=d2-d1+1;
  int *temp=new int[d1];
  int a=pow(2,d1-1);
  while(counter<times)
   { int j=0;
     if(counter==0)
      {
     for(int i=times-counter-1;i<d2-counter;i++)
      {  temp[j]=B[i];
  j++;
      }
      num1=bintodec(temp,j);
      }
      int num2=poly;
      if(counter!=0)
       num1=k;
     if(num1>=a)
       k=num1^num2;
     else
       k=num1;

     if(d2-d1-counter-1>=0)
     {
     if(B[d2-d1-counter-1]==1)
      k=k*2+1;
     else
      k=k*2;
     }
   counter++;
    }
  if(k==0)
    cout<<"MESSAGE TRANSMITTED SUCCESSFULLY\n"<<endl;
  else
    cout<<"ERROR IN TRANSMISSION\n"<<endl;

}
void main()
{ clrscr();
  int message,genpoly,ch=1;
  cout<<"enter the number to be transmitted"<<endl;
  cin>>message;
  cout<<"Enter the generator polynomial number"<<endl;
  cin>>genpoly;
  int gp=sender(message,genpoly);

  while(ch==1 || ch==2)
  {
  cout<<"MENU"<<endl;
  cout<<"1-SUCCESSFUL TRANSMISSION"<<endl;
  cout<<"2-ERROR IN TRANSMISSION"<<endl;
  cout<<"PRESS ANY OTHER KEY TO EXIT"<<endl;
  cout<<"Enter your choice"<<endl;
  cin>>ch;
   if(ch==1)
  { cout<<"TRANSMITTING MESSAGE .......\n"<<endl;
    delay(5000);
    receiver(gp,genpoly);
    int *B=dectobin(message);
    int dig=digitinbin(message);
    cout<<"The transmitted message is ";
      for(int i=dig-1;i>=0;i--)
 cout<<B[i];
    cout<<"\n"<<endl;
  }
   else
   if(ch==2)
  {  cout<<"TRANSMITTING MESSAGE .......\n"<<endl;
    delay(5000);
    receiver(gp+1,genpoly);
     cout<<endl;
   }
}

 cout<<"PROGRAM ENDS"<<endl;
getch();
}

/*     OUTPUT

enter the number to be transmitted
729
Enter the generator polynomial number
19
MENU
1-SUCCESSFUL TRANSMISSION
2-ERROR IN TRANSMISSION
PRESS ANY OTHER KEY TO EXIT
Enter your choice
1
TRANSMITTING MESSAGE .......

MESSAGE TRANSMITTED SUCCESSFULLY

The transmitted message is 1011011001

MENU
1-SUCCESSFUL TRANSMISSION
2-ERROR IN TRANSMISSION
PRESS ANY OTHER KEY TO EXIT
Enter your choice
2
TRANSMITTING MESSAGE .......

ERROR IN TRANSMISSION


MENU
1-SUCCESSFUL TRANSMISSION
2-ERROR IN TRANSMISSION
PRESS ANY OTHER KEY TO EXIT
Enter your choice
4
PROGRAM ENDS

*/