## Name

scalb, scalbf, scalbl — multiply floating-point number by integral power of radix (OBSOLETE)

## Synopsis

`#include <math.h>`
 ```double scalb(``` double x, double exp`)`;

 ```float scalbf(``` float x, float exp`)`;

 ```long double scalbl(``` long double x, long double exp`)`;

Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
`scalb`():
`_XOPEN_SOURCE` >= 500 || /* Since glibc 2.19:
*/ `_DEFAULT_SOURCE` || /* Glibc <= 2.19:
*/ `_BSD_SOURCE` || `_SVID_SOURCE`
`scalbf`(), `scalbl`():
`_XOPEN_SOURCE` >= 600 || /* Since glibc 2.19:
*/ `_DEFAULT_SOURCE` || /* Glibc <= 2.19:
*/ `_BSD_SOURCE` || `_SVID_SOURCE`
Note Link with `−lm`.

## DESCRIPTION

These functions multiply their first argument `x` by `FLT_RADIX` (probably 2) to the power of `exp`, that is:

```    x * FLT_RADIX ** exp
```

The definition of `FLT_RADIX` can be obtained by including `<``float.h``>`

## RETURN VALUE

On success, these functions return `x` * `FLT_RADIX` ** `exp`.

If `x` or `exp` is a NaN, a NaN is returned.

If `x` is positive infinity (negative infinity), and `exp` is not negative infinity, positive infinity (negative infinity) is returned.

If `x` is +0 (−0), and `exp` is not positive infinity, +0 (−0) is returned.

If `x` is zero, and `exp` is positive infinity, a domain error occurs, and a NaN is returned.

If `x` is an infinity, and `exp` is negative infinity, a domain error occurs, and a NaN is returned.

If the result overflows, a range error occurs, and the functions return `HUGE_VAL`, `HUGE_VALF`, or `HUGE_VALL`, respectively, with a sign the same as `x`.

If the result underflows, a range error occurs, and the functions return zero, with a sign the same as `x`.

## ERRORS

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: `x` is 0, and `exp` is positive infinity, or `x` is positive infinity and `exp` is negative infinity and the other argument is not a NaN

`errno` is set to EDOM. An invalid floating-point exception (`FE_INVALID`) is raised.

Range error, overflow

`errno` is set to ERANGE. An overflow floating-point exception (`FE_OVERFLOW`) is raised.

Range error, underflow

`errno` is set to ERANGE. An underflow floating-point exception (`FE_UNDERFLOW`) is raised.

## ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

 Interface Attribute Value `scalb`(), `scalbf`(), `scalbl`() Thread safety MT-Safe

## CONFORMING TO

`scalb`() is specified in POSIX.1-2001, but marked obsolescent. POSIX.1-2008 removes the specification of `scalb`(), recommending the use of scalbln(3), scalblnf(3), or scalblnl(3) instead. The `scalb`() function is from 4.3BSD.

`scalbf`() and `scalbl`() are unstandardized; `scalbf`() is nevertheless present on several other systems

## BUGS

Before glibc 2.20, these functions did not set `errno` for domain and range errors.

This page is part of release 5.11 of the Linux `man-pages` project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man−pages/.