#include <conio.h>
#include <iostream.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

int get_binary();
int get_hex();
int get_decimal();

void display(int);
void display_binary(int);
void display_hex(int);
void display_decimal(int);
void help(void);

void print_binary_digit(int);
void print_hex_digit(int);

void main(void)
{
  char c;
  int x;
  int done = 0;

  cout << "\nRadix Converter\n";
  help();

  while(!done) {
    cout << "Command: ";
    c = getch();
    cout << c << "\n";
    switch(c)
      {
      case 'b':
	cout << "Binary number: ";
	x = get_binary();
	display(x);
	break;

      case 'h':
	cout << "Hex number: ";
	x = get_hex();
	display(x);
	break;

      case 'd':
	cout << "Decimal number: ";
	x = get_decimal();
	display(x);
	break;

      case '?':
	help();
	break;

      case 'q':
	done = 1;
	break;

      default:
	help();
	break;
      }
  }
}

void help(void)
{
  cout << "\nEnter d for decimal\n"
       << "      h for hex\n"
       << "      b for binary\n"
       << "      q to quit\n"
       << "      ? for help\n\n";

}

void display(int x)
{
  cout << "\n\n";
  display_hex(x);
  display_decimal(x);
  display_binary(x);
  cout << "\n";
}


int ctoi(char c)
{
  switch(c) {
  case '0': return(0);
  case '1': return(1);
  case '2': return(2);
  case '3': return(3);
  case '4': return(4);
  case '5': return(5);
  case '6': return(6);
  case '7': return(7);
  case '8': return(8);
  case '9': return(9);
  case 'a':
  case 'A': return(10);
  case 'b':
  case 'B': return(11);
  case 'c':
  case 'C': return(12);
  case 'd':
  case 'D': return(13);
  case 'e':
  case 'E': return(14);
  case 'f':
  case 'F': return(15);
  default: cout << "ctoi: error nonnumeric character\n"; break;
  }
}

int get_binary(void)
{
  int bin = 0;
  char c;

  while(1) {
    c = getch();

    if(c == '0' || c == '1') {
      cout << c;
      bin = bin*2 + ctoi(c);
    } else if(c == 13) {
      return(bin);
    }
  }
}


int get_decimal(void)
{
  int dec = 0;
  char c;

  while(1) {
    c = getch();

    if(isdigit(c)) {
      cout << c;
      dec = dec*10 + ctoi(c);
    } else if(c == 13){
      return(dec);
    }
  }
}


int get_hex()
{
  int hex = 0;
  char c;

  while(1) {
    c = getch();

    if(isxdigit(c)) {
      cout << c;
      hex = hex*16 + ctoi(c);
    } else if(c == 13) {
      return(hex);
    }
  }
}

void display_binary(int x)
{
  int i;
  int nonzero = 0;

  cout << "Binary:  ";

  for(i = 31; i >= 0; i--) {
    nonzero += (x >> i) & 1;
    if(nonzero)
      print_binary_digit((x >> i) & 1);
  }

  if(x == 0)
    print_binary_digit(0);

  cout << "\n";
}


void display_decimal(int x)
{
  cout << "Decimal: " << x << "\n";
}


void display_hex(int x)
{
  int i;
  int nonzero = 0;

  cout << "Hex:     ";
  for(i = 7; i >= 0; i--) {
    nonzero += (x >> (i * 4)) & 0xF;
    if(nonzero)
      print_hex_digit((x >> (i * 4)) & 0xF);
  }

  if(x == 0)
    print_hex_digit(0);

  cout << "\n";
}

void print_binary_digit(int x)
{
  switch(x) {
  case 0: cout << "0"; break;
  case 1: cout << "1"; break;
  default:
    cout << "Error, print_digit accepts 0-15 only\n";
    exit(-1);
    break;
  }
}

void print_hex_digit(int x)
{
  switch(x) {
  case 0: cout << "0"; break;
  case 1: cout << "1"; break;
  case 2: cout << "2"; break;
  case 3: cout << "3"; break;
  case 4: cout << "4"; break;
  case 5: cout << "5"; break;
  case 6: cout << "6"; break;
  case 7: cout << "7"; break;
  case 8: cout << "8"; break;
  case 9: cout << "9"; break;
  case 10: cout << "A"; break;
  case 11: cout << "B"; break;
  case 12: cout << "C"; break;
  case 13: cout << "D"; break;
  case 14: cout << "E"; break;
  case 15: cout << "F"; break;
  default:
    cout << "Error, print_hex_digit accepts 0-15 only\n";
    exit(-1);
    break;
  }
}