# How to turn on a particular bit in a number?

• Difficulty Level : Basic
• Last Updated : 05 May, 2021

Given a number n and a value k, turn on the kâ€™th bit in n.
Examples:

```Input:  n = 4, k = 2
Output: 6

Input:  n = 3, k = 3
Output: 7

Input:  n = 64, k = 4
Output: 72

Input:  n = 64, k = 5
Output: 80```

The idea is to use bitwise << and | operators. Using expression “(1 << (k â€“ 1))â€œ, we get a number which has all bits unset, except the kâ€™th bit. If we do bitwise | of this expression with n, we get a number which has all bits same as n except the kâ€™th bit which is 1.
Below is the implementation of above idea.

## C++

 `// CPP program to turn on a particular bit``#include ``using` `namespace` `std;` `// Returns a number that has all bits same as n``// except the k'th bit which is made 1``int` `turnOnK(``int` `n, ``int` `k)``{``    ``// k must be greater than 0``    ``if` `(k <= 0)``        ``return` `n;` `    ``// Do | of n with a number with all``    ``// unset bits except the k'th bit``    ``return` `(n | (1 << (k - 1)));``}` `// Driver program to test above function``int` `main()``{``    ``int` `n = 4;``    ``int` `k = 2;``    ``cout << turnOnK(n, k);``    ``return` `0;``}`

## Java

 `// Java program to turn on a particular``// bit``class` `GFG {``    ` `    ``// Returns a number that has all``    ``// bits same as n except the k'th``    ``// bit which is made 1``    ``static` `int` `turnOnK(``int` `n, ``int` `k)``    ``{``        ` `        ``// k must be greater than 0``        ``if` `(k <= ``0``)``            ``return` `n;``    ` `        ``// Do | of n with a number with``        ``// all unset bits except the``        ``// k'th bit``        ``return` `(n | (``1` `<< (k - ``1``)));``    ``}``    ` `    ``// Driver program to test above``    ``// function``    ``public` `static` `void` `main(String [] args)``    ``{``        ``int` `n = ``4``;``        ``int` `k = ``2``;``        ``System.out.print(turnOnK(n, k));``    ``}``}` `// This code is contributed by Smitha`

## Python 3

 `# Python 3 program to turn on a``# particular bit` `# Returns a number that has all``# bits same as n except the k'th``# bit which is made 1``def` `turnOnK(n, k):` `    ``# k must be greater than 0``    ``if` `(k <``=` `0``):``        ``return` `n` `    ``# Do | of n with a number``    ``# with all unset bits except``    ``# the k'th bit``    ``return` `(n | (``1` `<< (k ``-` `1``)))` `# Driver program to test above``# function``n ``=` `4``k ``=` `2``print``(turnOnK(n, k))` `# This code is contributed by``# Smitha`

## C#

 `// C# program to turn on a particular``// bit``using` `System;` `class` `GFG {``    ` `    ``// Returns a number that has all``    ``// bits same as n except the k'th``    ``// bit which is made 1``    ``static` `int` `turnOnK(``int` `n, ``int` `k)``    ``{``        ` `        ``// k must be greater than 0``        ``if` `(k <= 0)``            ``return` `n;``    ` `        ``// Do | of n with a number``        ``// with all unset bits except``        ``// the k'th bit``        ``return` `(n | (1 << (k - 1)));``    ``}``    ` `    ``// Driver program to test above``    ``// function``    ``public` `static` `void` `Main()``    ``{``        ``int` `n = 4;``        ``int` `k = 2;``        ``Console.Write(turnOnK(n, k));``    ``}``}` `// This code is contributed by Smitha`

## PHP

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## Javascript

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Output:

`6`

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