Chapter-4/4-27.cpp

   1 /*C++ How to Program, 9/E, by Paul Deitel & Harvey Deitel.
   2
   3 Solution of exercise 4.27:
   4 (Printing the Decimal Equivalent of a Binary Number) Input an integer
   5 containing only 0s and 1s (i.e., a "binary" integer) and print its decimal
   6 equivalent. Use the modulus and division operators to pick off the "binary"
   7 number's digits one at a time from right to left. Much as in the decimal
   8 number system, where the rightmost digit has a positional value of 1, the next
   9 digit left has a positional value of 10, then 100, then 1000, and so on, in
  10 the binary number system the rightmost digit has a positional value of 1, the
  11 next digit left has a positional value of 2, then 4, then 8, and so on. Thus
  12 the decimal number 234 can be interpreted as 2 * 100 + 3 * 10 + 4 * 1. The
  13 decimal equivalent of binary 1101 is 1 * 1 + 0 * 2 + 1 * 4 + 1 * 8 or 1 + 0 +
  14 4 + 8, or 13. [Note: To learn more about binary numbers, refer to Appendix D.]
  15
  16 Written by Juan Carlos Moreno (jcmhsoftware@gmail.com), 2023-03-08.
  17 */
  18
  19 #include <iostream>
  20
  21 using namespace std;
  22
  23 int main()
  24 {
  25     int binary_number, digit, number, decimal_equivalent = 0;
  26     int power_of_ten = 1000000000, power_of_two = 1024;
  27
  28     cout << "Input the binary integer (only 0s and 1s): ";
  29     cin >> binary_number;
  30     number = binary_number;
  31
  32     while ((power_of_ten >= 1) && (power_of_two >= 1))
  33     {
  34         digit = number / power_of_ten;
  35         number = number % power_of_ten;
  36         power_of_ten = power_of_ten / 10;
  37         power_of_two = power_of_two / 2;
  38         decimal_equivalent = decimal_equivalent + digit*power_of_two;
  39     }
  40
  41     cout << "The decimal equivalent of binary " << binary_number << " is "
  42          << decimal_equivalent << "." << endl;
  43
  44     return 0;
  45 }