Returns the largest integer less than or equal to the argument.
    Format
      #include  <math.h>
      double floor  (double x);
      float floorf  (float x); (Integrity servers, Alpha)
      long double floorl  (long double x);
                          (Integrity servers, Alpha)
1 – Argument
 x
    A real value.
2 – Return Value
    n                  The largest integer less than or equal to the
                       argument.