hamming.c

#include <stdio.h>
int data[4], encoded[7], edata[7], syn[3];
int gmatrix[4][7] = {{0, 1, 1, 1, 0, 0, 0},
                     {1, 0, 1, 0, 1, 0, 0},
                     {1, 1, 0, 0, 0, 1, 0},
                     {1, 1, 1, 0, 0, 0, 1}};
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}};
int main() {
  int i, j;
  printf("Hamming Code encoding\n");
  printf("Enter the 4 bit data (one by one): \n");
  for (i = 0; i < 4; i++) scanf("%d", &data[i]);
  printf("Generator Matrix\n");
  for (i = 0; i < 4; i++) {
    for (j = 0; j < 7; j++) {
      printf("%d", gmatrix[i][j]);
    }
    printf("\n");
  }
  printf("\n\nEncoded data : ");
  for (i = 0; i < 7; i++) {
    for (j = 0; j < 4; j++) encoded[i] ^= (data[j] * gmatrix[j][i]);
    printf("%d", encoded[i]);
  }
  printf("\n\nHamming Code Decoding \n\n");
  printf("Enter the encoded bit receieved (one by one) :\n");
  for (i = 0; i < 7; i++) scanf("%d", &edata[i]);
  printf("Syndrome = ");
  for (i = 0; i < 3; i++) {
    for (j = 0; j < 7; j++) syn[i] ^= (edata[j] * hmatrix[i][j]);
    printf("%d", syn[i]);
  }
  for (j = 0; j <= 7; j++)
    if (syn[0] == hmatrix[0][j] && syn[1] == hmatrix[1][j] &&
        syn[2] == hmatrix[2][j])
      break;
  if (j == 7)
    printf("\n\nThe code is error free\n");
  else {
    printf("\n\nError Receieved at bit no %d of the data\n\n", j + 1);
    edata[j] = !edata[j];
    printf("The correct data should be : ");
    for (i = 0; i < 7; i++) printf("%d", edata[i]);
  }
  printf("\n\n");
  return 0;
}