C++ Program to Convert Binary Number to Decimal and vice-versa

Example 1: C++ Program to Convert Binary Number to Decimal

// convert binary to decimal

#include <iostream>
#include <cmath>

using namespace std;

// function prototype
int convert(long long);

int main() {
  long long n;
  cout << "Enter a binary number: ";
  cin >> n;
  cout << n << " in binary = " << convert(n) << " in decimal";
  return 0;
}

// function definition
int convert(long long n) {
  int dec = 0, i = 0, rem;

  while (n!=0) {
    rem = n % 10;
    n /= 10;
    dec += rem * pow(2, i);
    ++i;
  }

  return dec;
}

Output

Enter a binary number: 1101
1101 in binary = 13 in decimal

In the program, we have included the header file cmath to perform mathematical operations in the program.

We ask the user to enter a binary number and pass it to the convert() function to convert it decimal.

Suppose n = 1101. Let's see how the while loop in the convert() function works.

So, 1101 in binary is 13 in decimal.

Now, let's see how we can change the decimal number into a binary number.

Example 2: C++ Program to convert decimal number to binary

// convert decimal to binary

#include <iostream>
#include <cmath>
using namespace std;

long long convert(int);

int main() {
  int n, bin;
  cout << "Enter a decimal number: ";
  cin >> n;
  bin = convert(n);
  cout << n << " in decimal = " << bin << " in binary" << endl ;
  return 0;
}

long long convert(int n) {
  long long bin = 0;
  int rem, i = 1;

  while (n!=0) {
    rem = n % 2;
    n /= 2;
    bin += rem * i;
    i *= 10;
  }

  return bin;
}

Output

Enter a decimal number: 13
13 in decimal = 1101 in binary

Suppose n = 13. Let's see how the while loop in the convert() function works.

Thus, 13 in decimal is 1101 in binary.