Related Articles

# 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 k’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 – 1))“, we get a number which has all bits unset, except the k’th bit. If we do bitwise | of this expression with n, we get a number which has all bits same as n except the k’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

 ``

## Javascript

 ``
Output:
`6`

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

My Personal Notes arrow_drop_up