Today we will learn Program to Convert Decimal to Binary in C++ and also convert Binary to Decimal number. Before start learning, you should have a little bit of knowledge of Binary and decimal Numbers.

### What is Binary Number?

The Binary Number is number which has base 2. which consists of only two numerical symbols ‘1’ and ‘0’ and each digit is referred to as a ‘Bit’.

For Example 5 in binary can be written as 0101.

### What is Decimal Number?

The number which has base 10 is called a Decimal Number system.

For Example 0101=2^3*0+2^2*1+2^1*0+2^0*1=0+4+0+1=5.

There are so many ways to convert Decimal to binary and vice versa. we will see it one by one.

## 1. Program to convert Decimal to Binary in C++

In this program, we will ask the user to enter the number which user wants to convert into binary.

Decimal to Binary Conversion Algorithm:

1 Step: At first divide the number by 2 by using modulus operator ‘%’ and store the remainder in the array.

2 Step: divide that number by 2.

3 Step: Now repeat the step until the number is greater than 0.

```//Learnprogramo - programming made simple
#include <iostream>
#include <cmath>
using namespace std;
long long convertDecimalToBinary(int);
int main()
{
int n, binaryNumber;
cout << "Enter a decimal number: ";
cin >> n;
binaryNumber = convertDecimalToBinary(n);
cout << n << " in decimal = " << binaryNumber << " in binary" << endl ;
return 0;
}
long long convertDecimalToBinary(int n)
{
long long binaryNumber = 0;
int remainder, i = 1, step = 1;
while (n!=0)
{
remainder = n%2;
cout << "Step " << step++ << ": " << n << "/2, Remainder = " << remainder << ", Quotient = " << n/2 << endl;
n /= 2;
binaryNumber += remainder*i;
i *= 10;
}
return binaryNumber;
}```

Output:

## 2. Program to Convert Binary to Decimal in C++

In this program, we will convert the Binary input to Decimal.

Binary to Decimal Conversion Algorithm:

1 Step: Take a Binary Input to convert into Decimal.

2 Step: Multiply each binary digit starting from last with the power of 2 i.e(2^0,2^1).

3 Step: make an addition of the multiplied digits.

4 Step: Thus the addition gives the Decimal output.

```//Learnprogramo - programming made simple
#include <iostream>
#include <cmath>
using namespace std;
int convertBinaryToDecimal(long long);
int main()
{
long long n;
cout << "Enter a binary number: ";
cin >> n;
cout << n << " in binary = " << convertBinaryToDecimal(n) << "in decimal";
return 0;
}
int convertBinaryToDecimal(long long n)
{
int decimalNumber = 0, i = 0, remainder;
while (n!=0)
{
remainder = n%10;
n /= 10;
decimalNumber += remainder*pow(2,i);
++i;
}
return decimalNumber;
}```

Output:

## 3. Decimal to Binary Conversion Using Bitwise Operator

```//Learnprogramo - programming made simple
#include <iostream>
using namespace std;
int decToBinary(int n)
{
for (int i = 31; i >= 0; i--) {
int k = n >> i;
if (k & 1)
cout << "1";
else
cout << "0";
}
}
int main()
{
//size of integer asumed as 32 bits
int n = 32;
decToBinary(n);
} ```

Output:

## 4. Decimal to Binary Without Using Array

```//Learnprogramo - programming made simple
#include <cmath>
#include <iostream>
using namespace std;
#define ull unsigned long long int
int decimalToBinary(int N)
{
ull B_Number = 0;
int cnt = 0;
while (N != 0) {
int rem = N % 2;
ull c = pow(10, cnt);
B_Number += rem * c;
N /= 2;
cnt++;
}
return B_Number;
}
int main()
{
int N = 15;
cout << decimalToBinary(N);
return 0;
} ```

Output: