Guidelines for Using the #define Statement
The following rules apply to the #define statement:
• The #define statement must be used by itself on one line.
• If no expression is given for a macro variable in a #define statement, then the preprocessor creates a macro variable with no value.
• Only one macro variable can be created in each #define statement.
• If you #define a macro variable that already exists, then the existing macro variable is redefined with a new value. Therefore, the following statement is valid and increments $a:
#define $a $a+1
• Multiple #defines of the same variable are permitted.
• Character macro variables cannot contain embedded single quotation marks.