# C++ Program for Decimal to Binary Conversion

## Program for Decimal to binary Conversion in C++

In this post, we will learn how to write a code for Decimal to Binary Conversion in C++. We will look at different ways for coding Decimal to Binary in C++.

## Various Methods discussed

• Method 1: Binary Bits stored in Array
• Method 2: Using mathematical operations to generate binary equivalent.

## Method 1

### C++ Code:

Run
```#include<iostream>
using namespace std;

void convertBinary(int num)
{
// creating an array to store binary equivalent
int binaryArray[32];

// using i to store binary bit at given array position
int i = 0;
while (num > 0) {

// resultant remainder is stored at given array position
binaryArray[i] = num % 2;
num = num / 2;
i++;
}

// printing binary array in reverse order
for (int j = i - 1; j >= 0; j--)
cout << binaryArray[j];
}

int main()
{
int n = 21;
convertBinary(n);
return 0;
}```

`10101`

## Method 2

### C++ Code:

Run
```#include<iostream>
using namespace std;

void convertBinary(int num)
{
// long long used to store large binary values
long long binary = 0;
int rem, i = 1;

while(num!=0)
{
rem = num % 2;
num /= 2;
binary += rem * i;

// moving to next position ex: units -> tens
i *= 10;
}
cout << binary;
}

int main()
{
int decimal_num = 21;
convertBinary(decimal_num);
return 0;
}```

`10101`