Given a binary number as input, we need to write a program to convert the given binary number into an equivalent decimal number.
Examples :
Input : 111
Output : 7
Input : 1010
Output : 10
Input: 100001
Output: 33
The idea is to extract the digits of a given binary number starting from the rightmost digit and keep a variable dec_value. At the time of extracting digits from the binary number, multiply the digit with the proper base (Power of 2) and add it to the variable dec_value. In the end, the variable dec_value will store the required decimal number.
For Example:
If the binary number is 111.
dec_value = 1*(2^2) + 1*(2^1) + 1*(2^0) = 7
The below diagram explains how to convert ( 1010 ) to equivalent decimal value:
Below is the implementation of the above idea :
C++
#include <iostream>
using namespace std;
int binaryToDecimal(int n)
{
int num = n;
int dec_value = 0;
int base = 1;
int temp = num;
while (temp) {
int last_digit = temp % 10;
temp = temp / 10;
dec_value += last_digit * base;
base = base * 2;
}
return dec_value;
}
int main()
{
int num = 10101001;
cout << binaryToDecimal(num) << endl;
}
|
Java
class GFG {
static int binaryToDecimal(int n)
{
int num = n;
int dec_value = 0;
int base = 1;
int temp = num;
while (temp > 0) {
int last_digit = temp % 10;
temp = temp / 10;
dec_value += last_digit * base;
base = base * 2;
}
return dec_value;
}
public static void main(String[] args)
{
int num = 10101001;
System.out.println(binaryToDecimal(num));
}
}
|
Python3
def binaryToDecimal(n):
num = n;
dec_value = 0;
base = 1;
temp = num;
while(temp):
last_digit = temp % 10;
temp = int(temp / 10);
dec_value += last_digit * base;
base = base * 2;
return dec_value;
num = 10101001;
print(binaryToDecimal(num));
|
C#
class GFG {
public static int binaryToDecimal(int n)
{
int num = n;
int dec_value = 0;
int base1 = 1;
int temp = num;
while (temp > 0) {
int last_digit = temp % 10;
temp = temp / 10;
dec_value += last_digit * base1;
base1 = base1 * 2;
}
return dec_value;
}
public static void Main()
{
int num = 10101001;
System.Console.Write(binaryToDecimal(num));
}
}
|
PHP
<?php
function binaryToDecimal($n)
{
$num = $n;
$dec_value = 0;
$base = 1;
$temp = $num;
while ($temp)
{
$last_digit = $temp % 10;
$temp = $temp / 10;
$dec_value += $last_digit
* $base;
$base = $base*2;
}
return $dec_value;
}
$num = 10101001;
echo binaryToDecimal($num), "\n";
?>
|
Javascript
<script>
function binaryToDecimal(n)
{
let num = n;
let dec_value = 0;
let base = 1;
let temp = num;
while (temp) {
let last_digit = temp % 10;
temp = Math.floor(temp / 10);
dec_value += last_digit * base;
base = base * 2;
}
return dec_value;
}
let num = 10101001;
document.write(binaryToDecimal(num) + "<br>");
</script>
|
Output:
169
Note: The program works only with binary numbers in the range of integers. In case you want to work with long binary numbers like 20 bits or 30 bit, you can use a string variable to store the binary numbers.
Below is a similar program which uses string variable instead of integers to store binary value:
C++
#include <iostream>
#include <string>
using namespace std;
int binaryToDecimal(string n)
{
string num = n;
int dec_value = 0;
int base = 1;
int len = num.length();
for (int i = len - 1; i >= 0; i--) {
if (num[i] == '1')
dec_value += base;
base = base * 2;
}
return dec_value;
}
int main()
{
string num = "10101001";
cout << binaryToDecimal(num) << endl;
}
|
Java
import java.io.*;
class GFG {
static int binaryToDecimal(String n)
{
String num = n;
int dec_value = 0;
int base = 1;
int len = num.length();
for (int i = len - 1; i >= 0; i--) {
if (num.charAt(i) == '1')
dec_value += base;
base = base * 2;
}
return dec_value;
}
public static void main(String[] args)
{
String num = new String("10101001");
System.out.println(binaryToDecimal(num));
}
}
|
Python3
def binaryToDecimal(n):
num = n;
dec_value = 0;
base1 = 1;
len1 = len(num);
for i in range(len1 - 1, -1, -1):
if (num[i] == '1'):
dec_value += base1;
base1 = base1 * 2;
return dec_value;
num = "10101001";
print(binaryToDecimal(num));
|
C#
using System;
class GFG {
static int binaryToDecimal(String n)
{
String num = n;
int dec_value = 0;
int base1 = 1;
int len = num.Length;
for (int i = len - 1; i >= 0; i--) {
if (num[i] == '1')
dec_value += base1;
base1 = base1 * 2;
}
return dec_value;
}
public static void Main()
{
String num = "10101001";
Console.WriteLine(binaryToDecimal(num));
}
}
|
PHP
<?php
function binaryToDecimal($n)
{
$num = $n;
$dec_value = 0;
$base = 1;
$len = strlen($num);
for ($i = $len - 1; $i >= 0; $i--)
{
if ($num[$i] == '1')
$dec_value += $base;
$base = $base * 2;
}
return $dec_value;
}
$num = "10101001";
echo binaryToDecimal($num), "\n";
?>
|
Javascript
<script>
function binaryToDecimal(n)
{
let num = n;
let dec_value = 0;
let base = 1;
let len = num.length;
for (let i = len - 1; i >= 0; i--) {
if (num[i] == '1')
dec_value += base;
base = base * 2;
}
return dec_value;
}
let num = "10101001";
document.write(binaryToDecimal(num) + "<br>");
</script>
|
Output :
169
Using pre-defined function:
C++
#include <iostream>
using namespace std;
int main()
{
char binaryNumber[] = "1001";
cout << stoi(binaryNumber, 0, 2);
return 0;
}
|
C
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
int main()
{
char binaryNumber[] = "1001";
int bin, dec = 0;
bin = atoi(binaryNumber);
for(int i = 0; bin; i++, bin /= 10)
if (bin % 10)
dec += pow(2, i);
printf("%d", dec);
return 0;
}
|
Java
public class GFG {
public static void main(String args[])
{
String binaryNumber = "1001";
System.out.println(Integer.parseInt(binaryNumber, 2));
}
}
|
Python3
n = input()
s = int(n, 2)
print(s)
|
C#
using System;
class GFG {
public static void Main()
{
int value = 1001;
Console.Write(Convert.ToInt32(value.ToString(), 2));
}
}
|
Javascript
<script>
var binaryNumber = "1001";
document.write(parseInt(binaryNumber, 2));
</script>
|
Output :
9
This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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