Synopsis
#include <math.h>
double floor(double x);
Description

floor computes the largest integer value not greater than x.

IEC 60559 math library behavior

floor(±0) is±0.
floor(±?) is ±?.

Portability

floor conforms to ISO/IEC 9899:1990 (C90) and ISO/IEC 9899:1999 (C99).