# scalb()

## Synopsis:

```#include <math.h>

double scalb( double x,
double n );
```

## Arguments:

x
The floating point number that you want to multiply by the exponent.
n
The exponent to apply to the radix of the machine's floating-point arithmetic.

## Library:

libm

Use the -l m option to qcc to link against this library.

## Description:

This function computes x × rn, where r is the radix of the machine's floating point arithmetic and n is a finite number. When r is 2, scalb() is equivalent to ldexp().

Note: We recommend that you use scalbn() because it computes by manipulating exponents, instead of using mock multiplications or additions.

## Returns:

x × rn

Note: If an error occurs, this function returns 0, but this is also a valid mathematical result. If you want to check for errors, set errno to 0, call the function, and then check errno again. This function doesn't change errno if no errors occurred.

## Examples:

```#include <stdio.h>
#include <errno.h>
#include <inttypes.h>
#include <math.h>
#include <fpstatus.h>

int main(int argc, char** argv)
{
double a, b, c, d;

a = 10;
b = 2;
c = scalb(a, b);
d = sqrt(c/a);
printf("Radix of machines fp arithmetic is %f \n", d);
printf("So %f = %f * (%f ^ %f) \n", c, a, d, b);

return(0);
}
```

produces the output:

```Radix of machines fp arithmetic is 2.000000
So 40.000000 = 10.000000 * (2.000000 ^ 2.000000)
```

## Classification:

Standard Unix; removed from POSIX.1-2008

Safety:
Cancellation point No
Interrupt handler No
Signal handler No