FLOOR(3) Linux Programmer's Manual FLOOR(3)
floor - largest integral value not greater than x
#include <math.h> double floor(double x);
The floor() function rounds x downwards to the nearest integer, returning that value as a double.
SVID 3, POSIX, BSD 4.3, ISO 9899
abs(3), fabs(3), ceil(3), rint(3) June 6, 1993 1