Program for Decimal to Binary Conversion

Given a decimal number as input, we need to write a program to convert the given decimal number into equivalent binary number.

Examples:

Input : 7
Output : 111

Input : 10
Output : 1010

Input: 33
Output: 100001

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

Algorithm:

Store the remainder when the number is divided by 2 in an array.
Divide the number by 2
Repeat the above two steps until the number is greater than zero.
Print the array in reverse order now.

For Example:
If the binary number is 10.
Step 1: Remainder when 10 is divided by 2 is zero. Therefore, arr[0] = 0.
Step 2: Divide 10 by 2. New number is 10/2 = 5.
Step 3: Remainder when 5 is divided by 2 is 1. Therefore, arr[1] = 1.
Step 4: Divide 5 by 2. New number is 5/2 = 2.
Step 5: Remainder when 2 is divided by 2 is zero. Therefore, arr[2] = 0.
Step 6: Divide 2 by 2. New number is 2/2 = 1.
Step 7: Remainder when 1 is divided by 2 is 1. Therefore, arr[3] = 1.
Step 8: Divide 1 by 2. New number is 1/2 = 0.
Step 9: Since number becomes = 0. Print the array in reverse order. Therefore the equivalent binary number is 1010.

Below diagram shows an example of converting the decimal number 17 to equivalent binary number.

Below is the implementation of above idea.

C/C++

// C++ program to convert a decimal
// number to binary number

#include <iostream>
using namespace std;

// function to convert decimal to binary
void decToBinary(int n)
{
    // array to store binary number
    int binaryNum[1000];

    // counter for binary array
    int i = 0;
    while (n > 0) {

        // storing remainder in binary array
        binaryNum[i] = n % 2;
        n = n / 2;
        i++;
    }

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

// Driver program to test above function
int main()
{
    int n = 17;
    decToBinary(n);
    return 0;
}

Java

// Java program to convert a decimal
// number to binary number
import java.io.*;

class GFG 
{
    // function to convert decimal to binary
    static void decToBinary(int n)
    {
        // array to store binary number
        int[] binaryNum = new int[1000];
 
        // counter for binary array
        int i = 0;
        while (n > 0) 
        {
            // storing remainder in binary array
            binaryNum[i] = n % 2;
            n = n / 2;
            i++;
        }
 
        // printing binary array in reverse order
        for (int j = i - 1; j >= 0; j--)
            System.out.print(binaryNum[j]);
    }
    
    // driver program
    public static void main (String[] args) 
    {
        int n = 17;
        decToBinary(n);
    }
}

// Contributed by Pramod Kumar

C#

// C# program to convert a decimal
// number to binary number
using System;
        
public class GFG 
{ 
    
    // function to convert decimal 
    // to binary
    static void decToBinary(int n)
    {
        // array to store binary number
        int[] binaryNum = new int[1000];

        // counter for binary array
        int i = 0;
        while (n > 0) 
        {
            // storing remainder in 
            // binary array
            binaryNum[i] = n % 2;
            n = n / 2;
            i++;
        }

        // printing binary array
        // in reverse order
        for (int j = i - 1; j >= 0; j--)
            Console.Write(binaryNum[j]);
    }
    
    // Driver Code
    public static void Main () 
    {
        int n = 17;
        decToBinary(n);
    }
}

// This code is contributed by Sam007.

Output:

We can use bitwise operators to do above job. Note that bitwise operators work faster than arithmetic operators used above.

C++

// CPP program to Decimal to binary conversion
// using bitwise operator
// Size of an integer is assumed to be 32 bits
#include <iostream>
using namespace std;

// Function that convert Decimal to binary
int decToBinary(int n)
{
    // Size of an integer is assumed to be 32 bits
    for (int i = 31; i >= 0; i--) {
        int k = n >> i;
        if (k & 1)
            cout << "1";
        else
            cout << "0";
    }
}

// driver code
int main()
{
    int n = 32;
    decToBinary(n);
}

PHP


<?php
// PHP program to Decimal to binary conversion
// using bitwise operator

// Size of an integer is assumed 
// to be 32 bits

// Function that convert Decimal to binary
function decToBinary($n)
{
    
    // Size of an integer is
    // assumed to be 32 bits
    for ( $i = 31; $i >= 0; $i--) 
    {
        $k = $n >> $i;
        if ($k & 1)
            echo "1";
        else
            echo "0";
    }
}

    // Driver Code
    $n = 32;
    decToBinary($n);

// This code is contributed by aj_36
?>

Output:

00000000000000000000000000100000

Thanks to ajay0007 for suggesting above solution.

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