Macro variables can
supply a variety of information, from operating system information,
to SAS session information, to any text string that you define. Updating
multiple references to a variable, data set, or text string is a simple
process if you use macro variables in your programs. Macro variables
are part of the SAS macro facility, which is a tool for extending
and customizing SAS and for reducing the amount of text that you must
enter in order to perform common tasks.
Values of macro variables
are stored in symbol tables. Values that are stored in the global
symbol table are always available. In order to substitute the value
of a macro variable in your program, you must reference that macro
variable by preceding the macro variable name with an ampersand. You
can reference a macro variable anywhere in a SAS program except within
data lines.