CRC receiver

// Include headers

#include<stdio.h>

#include<string.h>

// length of the generator polynomial

#define N strlen(gen_poly)

// data to be transmitted and received

char data[28];

// CRC value

char check_value[28];

// generator polynomial

char gen_poly[10];

// variables 

int data_length,i,j;

// function that performs XOR operation

void XOR(){

    // if both bits are the same, the output is 0

    // if the bits are different the output is 1

    for(j = 1;j < N; j++)

    check_value[j] = (( check_value[j] == gen_poly[j])?'0':'1');

    

}

// Function to check for errors on the receiver side

void receiver(){

// get the received data

    printf("Enter the received data: ");

    scanf("%s", data);

    printf("\n-----------------------------\n");

    printf("Data received: %s", data);

// Cyclic Redundancy Check

    crc();

// Check if the remainder is zero to find the error

    for(i=0;(i<N-1) && (check_value[i]!='1');i++);

        if(i<N-1)

            printf("\nError detected\n\n");

        else

            printf("\nNo error detected\n\n");

}

void crc(){

    // initializing check_value

    for(i=0;i<N;i++)

        check_value[i]=data[i];

    do{

    // check if the first bit is 1 and calls XOR function

        if(check_value[0]=='1')

            XOR();

// Move the bits by 1 position for the next computation

        for(j=0;j<N-1;j++)

            check_value[j]=check_value[j+1];

        // appending a bit from data

        check_value[j]=data[i++];

    }while(i<=data_length+N-1);

// loop until the data ends

}

int main()

{

    // get the data to be transmitted

    printf("\nEnter data to be transmitted: ");

    scanf("%s",data);

    printf("\n Enter the Generating polynomial: ");

    // get the generator polynomial

    scanf("%s",gen_poly);

    // find the length of data

    data_length=strlen(data);

    // appending n-1 zeros to the data

    for(i=data_length;i<data_length+N-1;i++)

        data[i]='0';

    printf("\n----------------------------------------");

// print the data with padded zeros

    printf("\n Data padded with n-1 zeros : %s",data);

    printf("\n----------------------------------------");

// Cyclic Redundancy Check

    crc();

// print the computed check value

    printf("\nCRC or Check value is : %s",check_value);

// Append data with check_value(CRC)  

    for(i=data_length;i<data_length+N-1;i++)

        data[i]=check_value[i-data_length];

    printf("\n----------------------------------------");

// printing the final data to be sent

    printf("\n Final data to be sent : %s",data);

    printf("\n----------------------------------------\n");

// Calling the receiver function to check errors

    receiver();

        return 0;

}