October 29, 2003 SIGNBIT 3

### NAME

signbit - test sign

### LIBRARY

Standard C Library (libc, -lc)

### SYNOPSIS

```int` signbit(```real-floating x`)

### DESCRIPTION

The signbit(``) macro determines whether the sign of its argument value ```x` is negative. An argument represented in a format wider than its semantic type is converted to its semantic type first. The determination is then based on the type of the argument.

#### IEEE754

The sign is determined for all values, including infinities, zeroes, and NaNs

#### VAX

The sign is determined for finites, true zeros, and dirty zeroes; for ROPs the sign is reported negative.

### RETURN VALUES

The signbit(``) macro returns a non-zero value if the sign of its value ```x` is negative. Otherwise 0 is returned.

### ERRORS

No errors are defined.

### SEE ALSO

fpclassify(3), isfinite(3), isnormal(3), math(3)

### STANDARDS

The signbit(``) macro conforms to ISO/IEC 9899:1999 (``ISO C99'') .