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

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
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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

 ` `

Output:

```6
```

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