ceil

#include <math.h>

double ceil (
  double val);   /* number to calculate ceiling for */

The ceil function calculates the smallest integer value that is greater than or equal to val.

The ceil function returns a float that contains the smallest integer value that is not less than val.

floor

#include <math.h>
#include <stdio.h> /* for printf */

void tst_ceil (void) {
  float x;
  float y;

  x = 45.998;
  y = ceil (x);

  printf ("CEIL(%f) = %f\n", x, y);

  /* output is "CEIL(45.998) = 46" */
}