Data Communication



  Checksum
  Cyclic Redundancy Check


Cyclic Redundancy Check 

#include<stdio.h> 
#include <stdlib.h>
int main() 
{
	int i,j,keylen,msglen;
    	char input[100], key[30],temp[30],quot[100],rem[30],key1[30];
    	printf("Enter Data: ");
	scanf("%s",input);    	
    	printf("Enter Key: ");
	scanf("%s",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]);
    	return(0);
}