The Enable CLI Interception of Control Characters routine
    requests the calling process's command language interpreter
    (CLI) to resume interception of the selected control characters
    when they are typed during an interactive terminal session.
    LIB$ENABLE_CTRL provides the same function as the DCL command
    SET CONTROL.

    Format

      LIB$ENABLE_CTRL  enable-mask [,old-mask]

1  –  Returns

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

2  –  Arguments

 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 HP
    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.