Boolean type parameter : Boolean « PL SQL Data Types « Oracle PL/SQL Tutorial

SQL>
SQL> CREATE OR REPLACE PROCEDURE plsb (str IN VARCHAR2, bool IN BOOLEAN)
  2  IS
  3  BEGIN
  4     IF bool
  5     THEN
  6        DBMS_OUTPUT.PUT_LINE (str || ' - TRUE');
  7     ELSIF NOT bool
  8     THEN
  9        DBMS_OUTPUT.PUT_LINE (str || ' - FALSE');
 10     ELSE
 11        DBMS_OUTPUT.PUT_LINE (str || ' - NULL');
 12     END IF;
 13  END plsb;
 14  /

SP2-0804: Procedure created with compilation warnings

21.13.Boolean
	21.13.1.	BOOLEAN
	21.13.2.	Boolean literals
	21.13.3.	Boolean variables can be assigned either directly by using values TRUE, FALSE, or NULL or as the results of logical expressions
	21.13.4.	How to assign a TRUE value to a variable of type boolean
	21.13.5.	Use BOOLEAN type variable
	21.13.6.	Use 'and' to connect two boolean expressions
	21.13.7.	Demonstrates the effects of NULLs on Boolean expressions
	21.13.8.	Boolean type parameter
	21.13.9.	Exit when a boolean conditioin
	21.13.10.	Logic operator and boolean value