The Control Mode routine controls the mode of the pasteboard.
    This includes buffering, minimal updating, whether the screen
    is cleared when the pasteboard is deleted, and whether tab
    characters are used for screen formatting.

    Format

      SMG$CONTROL_MODE  pasteboard-id [,new-mode] [,old-mode]

                        [,buffer-size]

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2  –  Arguments

 pasteboard-id

    OpenVMS usage:identifier
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference

    Specifies the pasteboard to be changed. The pasteboard-id
    argument is the address of an unsigned longword that contains
    the pasteboard identifier.

    The pasteboard identifier is returned by SMG$CREATE_PASTEBOARD.

 new-mode

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference

    Specifies the new control settings to be used. The optional
    new-mode argument is the address of an unsigned longword that
    contains the mode settings. A bit set to 1 forces that mode to be
    employed; a bit set to 0 inhibits that mode of operation.

    Valid settings are as follows:

    SMG$M_BUF_ENABLED  Enables buffering.
    SMG$M_CLEAR_       Causes the Screen Management Facility to clear
    SCREEN             the screen when the program exits if you have
                       not previously deleted the pasteboard.
    SMG$M_IGNORE       Allows you to delete the pasteboard even if
                       batching is in effect.
    SMG$M_MINUPD       Enables minimal update (the default).
    SMG$M_NOTABS       Causes the Screen Management Facility not to
                       use tab characters to format the screen.
    SMG$M_PROTECT      Protect pasteboard operations from AST
                       interrupts (the default).
    SMG$M_RELEASE_PBD  Allows you to change the pasteboard size
                       (using the SMG$CHANGE_PBD_CHARACTERISTICS
                       routine) and prevents the Screen Management
                       Facility from modifying anything on the screen
                       outside of the smaller pasteboard.

    All other bits must be 0 and are reserved for future use by VSI.

 old-mode

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference

    Receives the control settings that were in effect before calling
    this procedure. The optional old-mode argument is the address
    of an unsigned longword into which the former mode settings are
    written. A bit set to 1 indicates that the specified mode was
    employed; a bit set to 0 indicates that the mode was inhibited.

 buffer-size

    OpenVMS usage:word_unsigned
    type:         word (unsigned)
    access:       read only
    mechanism:    by reference

    Specifies the size of the buffer in bytes. The optional buffer-
    size argument is the address of an unsigned word that contains
    the size of the buffer. The buffer-size argument is used when
    buffering mode is enabled (SMG$M_BUF_ENABLED). The default and
    minimum buffer size is 256 bytes. The maximum value is 65535. The
    buffer-size value depends on user authorization file (UAF) values
    and is maximized with the SYSGEN parameter MAXBUF.