The CLASS statement names the classification variables to be used in the model. Typical classification variables are TREATMENT, SEX, RACE, GROUP, and REPLICATION. The CLASS statement is required, and it must appear before the MODEL statement.

By default, classification levels are determined from the entire formatted values of the CLASS variables. Note that this represents a slight change from previous releases in the way in which classification levels are determined. In releases prior to Version 9, classification levels were determined by using no more than the first 16 characters of the formatted values. If you wish to revert to this previous behavior you can use the TRUNCATE option on the CLASS statement. In any case, you can use formats to group values into levels.

See the discussion of the FORMAT procedure in the SAS Procedures Guide and the discussions for the FORMAT statement and SAS formats in SAS Language Reference: Concepts.

You can specify the following option in the CLASS statement after a slash(/):