The **`creal` function** is part of the `<complex.h>` header file in C. It is used to return the real part of a complex number of type `double`. The function takes in a single parameter: a `double complex` number. 

> A complex number has a **real** and an **imaginary** part.

The illustration below shows how `creal` works:

# Declaration

The `creal` function is defined as follows:

```C
double creal(double complex z);
```
It takes in a single parameter of type `double complex`.

# Example

The following code snippet shows how we can use the `creal` function. The code below outputs the real part of the complex number:

#include <stdio.h> // Including header file for printf function
#include <complex.h> // Including header file for creal function

int main(){

  double complex z = 1.0 + 3.0*I; // assign value to variable
  printf("The real part is %f", creal(z));
  return 0;
}

> `creal`, `crealf` and `creall` are similar functions.

* `creal` takes a `double` complex number and returns its `double` real
* `crealf` takes a `float` complex number and returns its`float` real
* `creall` takes a `long double` complex number and returns its `long double` real

What is creal in C?

Declaration

Example