Missing Values in SAS

Find out missing value of a vairable
http://www2.sas.com/proceedings/sugi31/025-31.pdf


Character missing values are represented by a single blank enclosed in quotes (‘ ‘).
Numeric missing values are represented by a single period (.).
Special numeric missing values are represented by a single period followed by a single letter or an underscore (for example .A, .S, .Z, ._).
IF VALUE <=.Z THEN PUT “*** Value is missing”;
the order of missing variable:: negative number > .z > .(letters) > . > _