Error detection and correction

error_detection_and_correction.c

#include <stdio.h>
#include <stdio.h>

char data[5];
int encoded[8], edata[7], syndrome[3];
int hmatrix[3][7] = {1, 0, 0, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1};
char gmatrix[4][8] = {"0111000", "1010100", "1100010", "1110001"};

int main() {
    int i = 0, j = 0;
    char choice;
    do {
        printf("Hamming Code Encoding\nEnter 4 bit data: ");
        scanf("%s", data);
        printf("\nGenerator Matrix:\n");

        for(i = 0; i < 4; i++) {
            printf("\t%s\n", gmatrix[i]);
        }

        printf("\nEncoded data:\n");
        for (i = 0; i < 7; i++) {
            for (j = 0; j < 4; j++) {
                encoded[i] += ( ((int)data[j]) * ((int)gmatrix[j][i]) );
            }
            encoded[i] %= 2;
            printf("%d ", encoded[i]);
        }

        printf("\n\nHamming Code Decoding\nEnter Encoded bits as recieved: ");
        
        for (i = 0; i < 7; i++) {
            scanf("%d", &edata[i]);
        }
        for (i = 0; i < 3; i++) {
            for (j = 0; j < 7; j++) {
                syndrome[i] += (edata[j]*hmatrix[i][j]);
            }
            syndrome[i] %= 2;
        }

        for (j = 0; j < 7; j++) {
            if ( (syndrome[0] == hmatrix[0][j]) && (syndrome[1] == hmatrix[1][j]) && (syndrome[2] == hmatrix[2][j]) ) {
                break;
            }
        }
        if (j != 7) {
            printf("Error Recieved at bit number %d of the data\n", j+1);
            edata[j] = !edata[j];
            printf("The correct data should be:\n");
            for (i = 0; i < 7; i++) {
                printf("%d", encoded[i]);
            }
        }
        else if (j ==7) {
            printf("Data is error free!\n");
        }

        printf("\n\nDo you want to continue? [y/n]: ");
        scanf("%s", &choice);

    } while(choice == 'y');
    return 0;
}