A SAS variable name can be up to 32 characters long. The first character must be a letter (A,B,C,...,Z) or underscore (_). Subsequent characters can be letters, numbers (0 to 9), or underscores. No blanks are allowed.
Two names (_N_ and _ERROR_) are reserved by the SAS System. To avoid conflicting with variable names sometimes used by SAS/LAB software, it is recommended that you not use names beginning with an underscore.