ceil( ) function is similar to the round( ) function except that it always rounds up
for positive numbers or down for negative numbers. For example ceil(3.8) will
generate the value 4, while ceil(3.2) will also generate the value 4.
floor( ) function is also similar to the round( ) function except that it always rounds
down for positive number or up for negative numbers. For example floor(3.8) will
generate the value 3, while floor(3.2) will also generate the value 3