[<< wikibooks] Rexx Programming/How to Rexx/identifier
Identifiers are the names used to represent variables, constants, functions and labels within a program.


== Identifiers can consist only of alphanumeric and underscore character combinations and some symbols ==
As with most programming languages, identifiers can consist of a combination of letters, digits, and underscores, but must not begin with a digit. In rexx, variable names may also contain symbols such as hooks, plings and underscores. Compound variables may also contain dot symbols.


== Valid and Invalid Identifiers ==


== Valid Identifiers ==
hi_score
lumpsum
Apples
counter2


== Invalid Identifiers ==
1st_score 	Not valid because it begins with a digit
postcode# 	Contains an illegal hash character
Incomplete$ 	Contains an illegal dollar symbol
double 	This is a keyword


== Case Sensitivity ==
The rexx interpreter is case insensitive. This means that identifier names and keywords containing lowercase letters are interpreted as being the same as those containing uppercase letters: