Library /sys$common/syshlp/helplib.hlb  —  MACRO  /ALPHA  Macros  Arguments
    Macros have two types of arguments: actual and formal. Actual
    arguments are the text given in the macro call after the name
    of the macro. Formal arguments are specified by name in the
    macro definition; that is, after the macro name in the .MACRO
    directive. Actual arguments in macro calls and formal arguments
    in macro definitions can be separated by commas (,),  tabs, or
    spaces.

    The number of actual arguments in the macro call can be less
    than or equal to the number of formal arguments in the macro
    definition. If the number of actual arguments is greater than
    the number of formal arguments, the assembler displays an error
    message.

    Formal and actual arguments normally maintain a strict positional
    relationship. That is, the first actual argument in a macro call
    replaces all occurrences of the first formal argument in the
    macro definition. This strict positional relationship can be
    overridden by using keyword arguments. See the section on keyword
    arguments.

    An example of a macro definition using formal arguments follows:

    .MACRO  STORE  ARG1,ARG2,ARG3
    .LONG   ARG1                     ; ARG1 is first argument
    .WORD   ARG3                     ; ARG3 is third argument
    .BYTE   ARG2                     ; ARG2 is second argument
    .ENDM   STORE

    The following two examples show possible calls and expansions of
    the macro previously defined:

    STORE   3,2,1                    ; Macro call
    .LONG   3                        ; 3 is first argument
    .WORD   1                        ; 1 is third argument
    .BYTE   2                        ; 2 is second argument

    STORE   X,X-Y,Z                  ; Macro call
    .LONG   X                        ; X is first argument
    .WORD   Z                        ; Z is third argument
    .BYTE   X-Y                      ; X-Y is second argument
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