bsd man page for floor

FLOOR(3M)																 FLOOR(3M)

NAME
       fabs, floor, ceil, rint - absolute value, floor, ceiling, and round-to-nearest functions

SYNOPSIS
       #include <math.h>

       double floor(x)
       double x;

       double ceil(x)
       double x;

       double fabs(x)
       double x;

       double rint(x)
       double x;

DESCRIPTION
       Fabs returns the absolute value |x|.

       Floor returns the largest integer no greater than x.

       Ceil returns the smallest integer no less than x.

       Rint returns the integer (represented as a double precision number) nearest x in the direction of the prevailing rounding mode.

NOTES
       On a VAX, rint(x) is equivalent to adding half to the magnitude and then rounding towards zero.

       In  the	default  rounding  mode,  to nearest, on a machine that conforms to IEEE 754, rint(x) is the integer nearest x with the additional
       stipulation that if |rint(x)-x|=1/2 then rint(x) is even.  Other rounding modes can make rint act  like	floor,	or  like  ceil,  or  round
       towards zero.

       Another way to obtain an integer near x is to declare (in C)
	      double x;     int k;    k = x;
       Most C compilers round x towards 0 to get the integer k, but some do otherwise.	If in doubt, use floor, ceil, or rint first, whichever you
       intend.	Also note that, if x is larger than k can accommodate, the value of k and the presence or absence of an integer overflow are  hard
       to predict.

SEE ALSO
       abs(3), ieee(3M), math(3M)

4th Berkeley Distribution					   May 12, 1986 							 FLOOR(3M)