ceil() is a Mathematical Function returns the smallest integer value that is not less than the specified number. In other words, it returns the Round Up value of a given number.

    float ceil( float num);
    double ceil( double num);
    long double ceil( long double num);

   #include <stdio.h>
   #include <math.h>
   int main()
   {
      cout << "The ceiled value of 2.2 is:: " 
                 << ceil(2.2) << endl;
      cout << "The ceiled value of -2.3 is:: " 
                 << ceil(-2.3) << endl;
      return 0;
   }

   The ceiled value of 2.2 is:: 3
   The ceiled value of -2.3 is:: -2

In the above example ceil() is used to round up the value of the number specified.