Prohibition on entering letters in the console in C ++ for real?

Question

C++ / C#

The essence of the task is the conversion of basic data types into binary code using bitwise operations.
You also need to disable the input of letters. For integers, I somehow did it, but what about real numbers, where there can be more than a hundred characters after the decimal point?
PS Do not judge strictly, programming is not very long

#include <iostream>
#include <conio.h>
using namespace std;

bool cnt_wrk() {
  char c;
  cout << endl << "1.Again | 2.Menu ";
  do {
    c = _getch();
  } while ((c != '1') && (c != '2'));
  cout << endl;
  if (c == '1')
    return 1;
  return 0;
}

union real_num {
  float value;
  char mass[sizeof(value)];
};

void output_real(real_num none) {
  for (int i = 3; i >= 0; i--) {
    for (int j = 0; j < 8; j++) {
      if ((none.mass[i] & (128 >> j)))
        cout << "1";
      else
        cout << "0";
    }
    cout << " ";
  }
}

long long ctrl_int(int count) {
  bool flag = false;
  long long none = 0;
  int t = 0;
  char c;
  do {
    c = _getch();
    if ((c >= '0') && (c <= '9')) {
      none = none * 10 + c - '0';
      cout << c;
      t++;
    }
    else if (c == '-') {
      cout << c;
      flag = true;
    }
  } while ((c != 13) && (count > t));
  cout << endl;
  if (flag)
    return none * (-1);
  return none;
}

long long input_int(const char* promt, long long lower_limit, long long upper_limit, int symbol) {
  long long value;
  do {
    cout << promt;
    value = ctrl_int(symbol);
    if (!((value >= lower_limit) && (value <= upper_limit))) 
      cout << "Error! ";
  } while (!((value >= lower_limit) && (value <= upper_limit)));
  return value;
}

void cnv(int separator) {
  unsigned long long bitwise = 0;
  long long v_int;
  long long v_Uint;
  long long v_lglg;
  long long value = 0;
  int count = 0;
  int v_bool;
  char v_char;

  do {
    if (separator == 1) {
      bitwise = 128;
      v_bool = input_int("Bool: ", 0, 1, 1);
      value = v_bool;
    }
    else if (separator == 2) {
      bitwise = 128;
      cout << "Char: ";
      v_char = _getche();
      cout << endl;
      value = v_char;
    }
    else if (separator == 3) {
      bitwise = 2147483648;
      v_int = input_int("Integer: ", -2147483648, 2147483647, 10);
      value = v_int;
    }
    else if (separator == 4) {
      bitwise = 2147483648;
      v_Uint = input_int("UInteger: ", 1, 4294967295, 10);
      value = v_Uint;
    }
    else if (separator == 5) {
      bitwise = 9223372036854775808;
      v_lglg = input_int("Long long: ", -9223372036854775807, 
        9223372036854775807, 19);
      value = v_lglg;
    }
    while (true) {
      if (value & bitwise)
        cout << "1";
      else
        cout << "0";
      count++;
      if (count % 8 == 0)
        cout << " ";
      if (bitwise == 1)
        break;
      bitwise >>= 1;
    }

  } while (cnt_wrk());
  cout << endl;
}

int main() {
  int type;
  float number;
  cout << "----MENU----" << '\n' << "1) Bool" <<
    '\n' << "2) Char" << '\n' << "3) Integer" <<
    '\n' << "4) Unsigned Integer" <<
    '\n' << "5) Long long" << '\n' << "6) Double" << endl;
  do {
    type = input_int("Select the Type ('0' to exit): ", 0, 6, 1);
    cout << endl;
    switch (type) {
    case 0:
      exit(0);
    case 1:
      cnv(1);
      break;
    case 2:
      cnv(2);
      break;
    case 3:
      cnv(3);
      break;
    case 4:
      cnv(4);
      break;
    case 5:
      cnv(5);
      break;
    case 6:
      cin >> number;
      real_num none;
      none.value = number;
      output_real(none);
      cout << endl;
    }
  } while (type);
}

Answer 1

Read a std::string. Check that it has a maximum of 1 '-' at the very beginning, then the first digit is not '0' (if the second is not ',', there is a maximum of one character ',' and it is not the first. Then use stringstream to read double.