main.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>

int qpow(int base, int p){
  if (p == 0) return 1;
  int value = base;
  for (; p > 1; --p) value *= base;
  return value;
}

int read_number(int read_base){
  char input[256] = {' '};
  fgets(input, sizeof(input), stdin);
  int i = sizeof(input) - 2, value = 0, base = 0, power = 0;
  if (read_base != 0) {
    base = read_base;
  } else {
     for(; i >= 0; i--){ // reading base
      if (input[i] == '\0' || input[i] == '\n') continue;
      else if (input[i] == 'x') break;
      else {
        base += (input[i] - '0') * qpow(10, power++);
      }
    }
    i--;
    power = 0;
  }
  for(; i >= 0; i--){ // reading base
    if (input[i] == ' ') break;
    
    if (input[i] >= 'A' && input[i] <= 'Z'){
      value += (input[i] - 'A' + 10) * qpow(base, power++);
    } else if (input[i] >= 'a' && input[i] <= 'z') {
      value += (input[i] - 'a' + 10) * qpow(base, power++);
    } else {
      value += (input[i] - '0') * qpow(base, power++); 
    }
  }
  return value;
}

void printAsBase(int number, int base){
  char out[256] = {' '};
  int i = 0;
  while (number != 0){
    int now = number % base;
    if (now > 9){
      out[i++] = 'A' - 10 + now;
    } else {
      out[i++] = '0' + now;
    }
    number /= base;
  }
  for (; i >= 0; i--){
    printf("%c", out[i]);
  }
}

int to_grey_code(int number){
  return number ^ (number >> 1);
}

int from_grey_code(int number) {
    int mask;
    for (mask = number >> 1; mask != 0; mask = mask >> 1) {
        number = number ^ mask;
    }
    return number;
}

int main(){
  printf("1. Convert number to base.\n");
  printf("2. Create Hamming's Code.\n");
  printf("3. Read Hamming's Code.\n");
  printf("4. Create Grey's Code.\n");
  printf("5. Read Grey's Code.\n");
  printf("6. exit\n");
  int option = 6, number, base;
  do {
    scanf("%i", &option);
    switch(option){
      case 1:
        printf("Enter number in format number|x|base example 123x16\n>");
        number = read_number(0);
        printf("Enter base\n>");
        scanf("%i", &base);
        printf("As base %i: ", base);
        printAsBase(number, base);
        printf("\n");
        break;
      case 2:
        break;
      case 3:
        break;
      case 4:
        printf("Enter number in format number|x|base example 123x16\n>");
        number = read_number(0);
        printf("Grey's code: ");
        printAsBase(to_grey_code(number), 2); 
        printf("\n"); 
        break;
      case 5:
        printf("Enter Grey's code\n>");
        number = read_number(2);
        printf("Enter base\n>");
        scanf("%i", &base);
        printAsBase(from_grey_code(number), base);
        printf("\n"); 
        break;
    }
  } while(option != 6);

  return 0;
}