CYCLIC REDUNDANCY CHECK (CRC)

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 import java.util.*;

  class crc
 {
   public static void main(String args[])
    {
      int data[],div[],ad[],n,m,i,j,rec[],flag=0;
      Scanner cin=new Scanner(System.in);

      System.out.print("Enter divisor length :");
      n=cin.nextInt();

      System.out.print("Enter data length :");
      m=cin.nextInt();
  
      div=new int[n+1];
      data=new int[m+1];
      ad=new int[m+n];
      rec=new int[m+n];
 
      System.out.print("Enter dataword :");
       for(i=1;i<=n;i++)
        {
         data[i]=cin.nextInt();
         ad[i]=data[i];
        }

      System.out.print("Enter divisor :");
     
      for(i=1;i<=n;i++)
        div[i]=cin.nextInt();



     for(i=1;i<=n;i++)
      {
       if(div[1]==ad[i])
        {
          for(j=0;j<n;j++)
          ad[i+j]=ad[i+j]^div[j+1];
        }
         else
        {
         for(j=0;j<n;j++)
          ad[i+j]=ad[i+j]^0;
        }
      }


     
    System.out.print("Codeword :");

    for(i=1;i<=n;i++)
         System.out.print(data[i]);
 
  
   for(i=n+1;i<=m+n-1;i++)
        System.out.print(ad[i]);
  
       System.out.println("Enter Received codeword :");
     for(i=1;i<m+n;i++)
        rec[i]=cin.nextInt();
       
      for(i=1;i<=n;i++)
      {
       if(div[1]==rec[i])
        {
          for(j=0;j<n;j++)
          rec[i+j]=rec[i+j]^div[j+1];
        }
         else
        {
         for(j=0;j<n;j++)
          rec[i+j]=rec[i+j]^0;
        }
      }   
       
     for(i=m+n-1;i>=1;i--)
     {
       if(rec[i]==1)
       {
           flag=1;
           System.out.println("Received codeword has error");
           break;
       }
      
       else
            continue;
     }  
    
     if(flag==0)  
       System.out.println("Received codeword is correct ");

    
  }

 }


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                     OUTPUT

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Enter divisor length :4
Enter data length :4
Enter dataword :1001
Enter divisor :1011
Codeword :1001110
Enter Received codeword :1001110
Received codeword is correct


Enter divisor length :4
Enter data length :4
Enter dataword :1001
Enter divisor :1011
Codeword :1001110
Enter Received codeword :1001111
Received codeword has error

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