# C++ Programming/Code/Standard C Library/Functions/frexp

#### frexp

editSyntax |
```
#include <cmath>
double frexp( double num, int* exp );
``` |

The function frexp() is used to decompose *num* into two parts: a mantissa between 0.5 and 1 (returned by the function) and an exponent returned as *exp*. Scientific notation works like this:

```
num = mantissa * (2 ^ exp)
```