Oracle Round-off and Rounding functions--floor,round,ceil,trunc use instructions __c language

Read the Electrictoolbox on Php,mysql,javascript several languages on the topic of taking integers, but also dots collation of Oracle's take the whole function description, this is the origin of this article.
floor--the number of digits to a given number
Sql> Select Floor (2345.67) from dual;
FLOOR (2345.67)
--------------
2345
ceil--returns the smallest integer greater than or equal to the number given
Sql> Select Ceil (3.1415927) from dual;
Ceil (3.1415927)
---------------
4
round--rounding according to specified precision
Sql> Select Round (3.1415926,4) from dual;
ROUND (3.1415926,4)
------------------
3.1416
trunc--to intercept a number according to the specified precision
Sql> Select Trunc (3.1415926,4) from dual;
ROUND (3.1415926,4)
------------------
3.1415