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

21.1.1.Block Structure
21.1.2.Your First PL/SQL Block
21.1.3.The slash character (/) at the end of the example executes the PL/SQL.
21.1.4.You can declare the whole string to be enclosed in quotes by using the construct q'!text!'
21.1.5.All identifiers within the same scope must be unique.
21.1.6.Building Expressions with Operators
21.1.7.PL/SQL datatypes
21.1.8.Variable Naming Rules
21.1.9.Introducing the Main Data type Groups