CRC

Cyclic Redundancy Check:

 #include<stdio.h>  
 #include<conio.h>  
 #include<string.h>  
 void main()  
 {  
      int i,j,keylen,msglen;  
      char input[100], key[30], temp[30], quot[100],rem[30], key1[30];  
      clrscr();  
      printf("Enter Data : ");  
      gets(input);  
      printf("Enter Key : ");  
      gets(key);  
      keylen = strlen(key);  
      msglen = strlen(input);  
      strcpy(key1,key);  
      for(i=0;i<keylen-1;i++)  
      {  
           input[msglen+i]='0';  
      }  
      for(i=0;i<keylen;i++)  
      temp[i] = input[i];  
      for(i=0;i<msglen;i++)  
      {  
           quot[i] = temp[0];  
           if(quot[i]=='0')  
           for(j=0;j<keylen;j++)  
           key[j]='0';  
           else  
           for(j=0;j<keylen;j++)  
           key[j] = key1[j];  
           for(j=keylen-1;j>0;j--)  
           {  
                if(temp[j]==key[j])  
                rem[j-1]='0';  
                else  
                rem[j-1]='1';  
           }  
           rem[keylen-1] = input[i+keylen];  
           strcpy(temp,rem);  
      }  
      strcpy(rem,temp);  
      printf("\nQuotient is : ");  
      for(i=0;i<msglen;i++)  
      printf("%c",quot[i]);  
      printf("\nRemainder is : ");  
      for(i=0;i<keylen - 1;i++)  
      printf("%c",rem[i]);  
      printf("\nFinal Data is : ");  
      for(i=0;i<msglen;i++)  
      printf("%c",input[i]);  
      for(i=0;i<keylen-1;i++)  
      printf("%c",rem[i]);  
      getch();  
 }  
   
   

OUTPUT :