The FORMAT statement
can use standard SAS formats or user-written formats that have been
previously defined in PROC FORMAT. A single FORMAT statement can associate
the same format with several variables, or it can associate different
formats with different variables. If a variable appears in multiple
FORMAT statements, SAS uses the format that is assigned last.
You use a FORMAT statement
in the DATA step to permanently associate a format with a variable.
SAS changes the descriptor information of the SAS data set that contains
the variable. You can use a FORMAT statement in some PROC steps, but
the rules are different. For more information, see
Base SAS Procedures Guide