Boolean « PL SQL Data Types « Oracle PL/SQL Tutorial

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