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

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 <iostream>` `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

`<?php` `// PHP 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` `function` `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 Code` ` ` `$n` `= 4;` ` ` `$k` `= 2;` ` ` `echo` `turnOnK(` `$n` `, ` `$k` `);` `// This code is contributed by m_kit` `?>` |

## Javascript

`<script>` ` ` `// Javascript 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` ` ` `function` `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)));` ` ` `}` ` ` ` ` `let n = 4;` ` ` `let k = 2;` ` ` `document.write(turnOnK(n, k));` `// This code is contributed by suresh07.` `</script>` |

**Output:**

6