# How to count set bits in a floating point number in C?

Given a floating point number, write a function to count set bits in its binary representation.

For example, floating point representation of 0.15625 has 6 set bits (See this). A typical C compiler uses single precision floating point format.

We can use the idea discussed here. The idea is to take address of the given floating point number in a pointer variable, typecast the pointer to char * type and process individual bytes one by one. We can easily count set bits in a char using the techniques discussed here.

Following is C implementation of the above idea.

## C

`#include <stdio.h>` `// A utility function to count set bits in a char.` `// Refer http://goo.gl/eHF6Y8 for details of this function.` `unsigned ` `int` `countSetBitsChar(` `char` `n)` `{` ` ` `unsigned ` `int` `count = 0;` ` ` `while` `(n)` ` ` `{` ` ` `n &= (n-1);` ` ` `count++;` ` ` `}` ` ` `return` `count;` `}` `// Returns set bits in binary representation of x` `unsigned ` `int` `countSetBitsFloat(` `float` `x)` `{` ` ` `// Count number of chars (or bytes) in binary representation of float` ` ` `unsigned ` `int` `n = ` `sizeof` `(` `float` `)/` `sizeof` `(` `char` `);` ` ` `// typecast address of x to a char pointer` ` ` `char` `*ptr = (` `char` `*)&x; ` ` ` `int` `count = 0; ` `// To store the result` ` ` `for` `(` `int` `i = 0; i < n; i++)` ` ` `{` ` ` `count += countSetBitsChar(*ptr);` ` ` `ptr++;` ` ` `}` ` ` `return` `count;` `}` `// Driver program to test above function` `int` `main()` `{` ` ` `float` `x = 0.15625;` ` ` `printf` `(` `"Binary representation of %f has %u set bits "` `, x,` ` ` `countSetBitsFloat(x));` ` ` `return` `0;` `}` |

**Output: **

Binary representation of 0.156250 has 6 set bits

This article is contributed by **Vineet Gupta**. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above