. Punctuation

The period (.) symbol ends all statements, including block header statements. The DO, FOR, and REPEAT statements can end with a period or a colon.

It is also serves as a separator between:

A filename and a filename extension (suffix) in most operating system platforms, for example, Letter.txt

The elements of a qualified database table or buffer field name, for example, Customer.CustNum or Sports2000.Customer or Sports2000.Customer.CustNum

The elements of an ABL package name or .NET namespace, for example, Progress.Lang, Progress.Windows, or System.Collections

An ABL package or .NET namespace and the name of a class or interface defined in that package or namespace, for example, Progress.Lang.Error, Progress.Windows.Form, or System.Collections.SortedList

See :: Punctuation for rules to help you decide whether to use period, colon, or double colon syntax.

See also 

: Punctuation, :: Punctuation, Type-name syntax