DECLARATIONS IN PL/SQL:

a) The program stores values in variable.
b) As the program executes, the values of variables can change but the values of Constants cannot change.
c) Declarations allocate storage space for a value, hence should be specified by a datatype, and name for further reference.
d) Any variable can be declared only in the declarative part of any PL/SQL block, subprogram or package.

   EX: 
        DECLARE
               AdmnDate            DATE;
               PatientName        VARCHAR2(30);
               BPCount            SMALLINT:=0;