When coding source statements, you need to be aware of what
    characters are acceptable to the assembler, and how the assembler
    interprets them. The following numbers and characters are
    accepted by the assembler:

    o  The letters of the alphabet, A to Z, uppercase and lowercase.
       By default, the assembler converts all lowercase letters
       to uppercase. This means it considers lowercase letters
       equivalent to uppercase letters.

       The assembler can operate in a case-sensitive mode. In case-
       sensitive mode, the assembler does not convert lowercase
       letters to uppercase letters. On OpenVMS and OpenVMS Alpha
       systems, you can select case-sensitive mode from the command
       line with the /NAMES=AS_IS qualifier.

    o  The digits 0 to 9.

    o  The special characters listed in the Special Characters Table
       which follows.

    Table 2 Special Characters Used in MACRO-64 Statements

              Character
       CharactName       Function

       _      Underscore Character in symbol names.
       $      Dollar     Character in symbol names.
              sign
       .      Period     Character in symbol names, current location
                         counter, and decimal point.
       :      Colon      Local label terminator.
       ::     Double     Global label terminator.
              colon
              sign       keyword argument terminator.
              equal
              sign
       #      Number     Literal value indicator.
              sign
       @      At sign    Arithmetic shift operator.
       ;      Semicolon  Comment field indicator.
       +      Plus       Unary plus operator and arithmetic addition
              sign       operator.
       -      Minus      Unary minus operator, arithmetic subtraction
              sign or    operator, and line continuation indicator.
              hyphen
       *      Asterisk   Arithmetic multiplication operator.
       /      Slash      Arithmetic division operator.
       &      Ampersand  Logical AND operator.
       !      ExclamationLogical inclusive OR operator.
              point
       \      Backslash  Logical exclusive OR and numeric conversion
                         indicator in macro arguments.
       ^      Circumflex Unary operators and macro argument
                         delimiter.
       ( )    ParenthesesDisplacement and register field delimiter in
                         an instruction operand. Argument delimiter
                         to a lexical operator.
       <>     Angle      Argument or expression grouping delimiters.
              brackets
       ?      Question   Created local label indicator in macro
              mark       arguments.
       '      Apostrophe Macro argument concatenation indicator.
       "      Double     Quoted literal delimiter.
              quote
       %      Percent    Delimits the beginning of a lexical
              sign       operator.
       (space)Space or   Separates source statement fields. Spaces
              tab        within expressions are otherwise ignored.
       (tab)
       ,      Comma      Separates symbolic arguments within the
                         operand field. Multiple expressions in the
                         operand field must be separated by commas.