command_context
    type:       $SCA_COMMAND_CONTEXT
    access:     read/write
    mechanism:  by reference

    SCA command context value.

 command_string
    type:       character string
    access:     read only
    mechanism:  by descriptor

    An SCA subsystem command.

 parameter_routine
    type:       procedure
    access:     read only
    mechanism:  by reference

    Routine that prompts for required parameters. You can specify
    LIB$GET_INPUT or a compatible routine. If a routine address of
    zero (0) is specified, commands with missing parameters fail and
    display a CLI error message.

 continuation_routine
    type:       procedure
    access:     read only
    mechanism:  by reference

    Routine that prompts for the remainder of a continued command
    (i.e., a command that ends with a hyphen). You can specify
    LIB$GET_INPUT or a compatible routine.

 continuation_prompt
    type:       character string
    access:     read only
    mechanism:  by descriptor

    Command continuation prompt string (e.g., SCA> ).

 user_argument
    type:       longword
    access:     read only
    mechanism:  by reference

    User-specified value to be passed to any action routine (other
    than CLI prompt routines) called by this routine.

 confirm_routine
    type:       procedure
    access:     read only
    mechanism:  by value

    Command confirmation prompt routine to be used by commands that
    support a /CONFIRM qualifier. You can specify SCA$GET_INPUT or
    a compatible routine. If this argument is omitted, the /CONFIRM
    qualifier is not supported.

 topic_routine
    type:       procedure
    access:     read only
    mechanism:  by value

    Help topic prompt routine. You can specify LIB$GET_INPUT or a
    compatible routine. If this routine returns an error, command
    processing is terminated. If this argument is omitted, no help
    prompting is performed.

 display_routine
    type:       procedure
    access:     read only
    mechanism:  by value

    Routine to be called to display one line of command output. You
    can specify SCA$PUT_OUTPUT or a compatible routine. If this
    routine returns an error, command processing is terminated. If
    this argument is omitted, no display routine is called.