enable-mask

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

    Bit mask indicating for which control characters LIB$ENABLE_
    CTRL is to enable interception. The enable-mask argument is the
    address of an unsigned longword containing this bit mask. Each
    of the 32 bits corresponds to one of the 32 possible control
    characters. If a bit is set, the corresponding control character
    is intercepted by the CLI. Currently, only bits 20 and 25,
    corresponding to Ctrl/T and Ctrl/Y, are recognized.

    The following mask is defined in symbol libraries supplied by VSI
    to specify the value of enable-mask:

    Symbol          Hex Value     Function

    LIB$M_CLI_      %X'00100000'  Enables Ctrl/T
    CTRLT
    LIB$M_CLI_      %X'02000000'  Enables Ctrl/Y
    CTRLY

    If a set bit does not correspond to a character that the CLI can
    intercept, an error is returned.

 old-mask

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

    Previous bit mask. The old-mask argument is the address of an
    unsigned longword containing the old bit mask. The old bit mask
    is of the same form as enable-mask.