# signbit() Function with Example in C++

C++ signbit() function: Here, we are going to learn about the signbit() function with example of cmath header in C++ programming language.
Submitted by IncludeHelp, on May 25, 2020

## C++ signbit() function

signbit() function is a library function of cmath header. It is used to check the sign of the given value. It accepts a parameter (float, double or long double) and returns 1 if the given value is negative; 0, otherwise.

Syntax of signbit() function:

In C99, it has been implemented as a macro,

```    signbit(x)
```

In C++11, it has been implemented as a function,

```    bool signbit (float x);
bool signbit (double x);
bool signbit (long double x);
```

Parameter(s):

• x – represents the value to check its sign.

Return value:

It returns 1 if x is negative; 0, otherwise.

Example:

```    Input:
double x = 10.0;

Function call:
signbit(x);

Output:
0

Input:
double x = -10.0;

Function call:
signbit(x);

Output:
1
```

### C++ code to demonstrate the example of signbit() function

```// C++ code to demonstrate the example of
// signbit() function

#include <iostream>
#include <cmath>
using namespace std;

// main() section
int main()
{
double x = 0.0;

x = 10.0;
cout << "signbit(" << x << "): " << signbit(x) << endl;

x = -10.0;
cout << "signbit(" << x << "): " << signbit(x) << endl;

x = 10.10;
cout << "signbit(" << x << "): " << signbit(x) << endl;

x = -10.10;
cout << "signbit(" << x << "): " << signbit(x) << endl;

x = 0.0;
cout << "signbit(" << x << "): " << signbit(x) << endl;

x = -10.0 / 2.5;
cout << "signbit(" << x << "): " << signbit(x) << endl;

x = 10.0 / -2.5;
cout << "signbit(" << x << "): " << signbit(x) << endl;

x = sqrt(-1);
cout << "signbit(" << x << "): " << signbit(x) << endl;

return 0;
}
```

Output

```signbit(10): 0
signbit(-10): 1
signbit(10.1): 0
signbit(-10.1): 1
signbit(0): 0
signbit(-4): 1
signbit(-4): 1
signbit(-nan): 1
```

Reference: C++ signbit() function