To round a real number up is to take the least integer which is not less than
the specified number, i.e. if the number is not already an integer move in the positive
direction on the number line (usually right) until you hit an integer. This operation
is also called taking the ceiling of a number (the 'ceil' function in C). For
example, to round up 3 gives 3, to round up 3.5 gives 4, to round up 7.2 gives 8, to round
up -0.2 gives 0, to round up -99.7 gives -99.

Compare to round down and round off.