Hamming_Code

#include <stdio.h>

// Function to calculate parity bits
void generateHammingCode(int data[], int code[]) {
    // Place data bits at non-parity positions: 3,5,6,7,9,10,11 (1-based)
    code[2] = data[0];
    code[4] = data[1];
    code[5] = data[2];
    code[6] = data[3];
    code[8] = data[4];
    code[9] = data[5];
    code[10] = data[6];

    // Calculate parity bits at positions 1, 2, 4, and 8 (0-based: 0,1,3,7)
    code[0] = code[2] ^ code[4] ^ code[6] ^ code[8] ^ code[10];
    code[1] = code[2] ^ code[5] ^ code[6] ^ code[9] ^ code[10];
    code[3] = code[4] ^ code[5] ^ code[6];
    code[7] = code[8] ^ code[9] ^ code[10];
}

// Function to detect and correct single-bit errors
int detectAndCorrect(int code[]) {
    int p1 = code[0] ^ code[2] ^ code[4] ^ code[6] ^ code[8] ^ code[10];
    int p2 = code[1] ^ code[2] ^ code[5] ^ code[6] ^ code[9] ^ code[10];
    int p4 = code[3] ^ code[4] ^ code[5] ^ code[6];
    int p8 = code[7] ^ code[8] ^ code[9] ^ code[10];

    int errorPos = p8 * 8 + p4 * 4 + p2 * 2 + p1 * 1;

    return errorPos;
}

int main() {
    int data[7];
    int code[11] = {0};

    printf("SENDER SIDE:\n");
    printf("Enter 7 data bits (space-separated, e.g., 1 0 1 1 0 0 1): ");
    for (int i = 0; i < 7; i++) {
        scanf("%d", &data[i]);
    }

    generateHammingCode(data, code);

    printf("Generated 11-bit Hamming Code (to send): ");
    for (int i = 0; i < 11; i++) {
        printf("%d ", code[i]);
    }

    printf("\n\nRECEIVER SIDE:\n");
    int receivedCode[11];
    printf("Enter the 11-bit Hamming code received (space-separated): ");
    for (int i = 0; i < 11; i++) {
        scanf("%d", &receivedCode[i]);
    }

    int errorPos = detectAndCorrect(receivedCode);
    if (errorPos == 0) {
        printf("\nNo error detected in received data.\n");
    } else {
        printf("\nError detected at position: %d\n", errorPos);
        receivedCode[errorPos - 1] ^= 1; // Correct the error
        printf("Corrected Code: ");
        for (int i = 0; i < 11; i++) {
            printf("%d ", receivedCode[i]);
        }
        printf("\n");
    }

    return 0;
}