Library /sys$common/syshlp/dbg$help.hlb DEBUG, EXAMINE, Qualifiers, /TMASK  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /TMASK[=(mask-address-expression)]
       /FMASK[=(mask-address-expression)]

    These qualifiers apply only to VAX vectorized programs. They
    enable you to specify a mask in order to display certain elements
    of a vector register (V0 to V15), or of an array in memory, while
    not displaying other elements.

    For example, when you examine the operands of a vector
    instruction (by using the /OPERANDS qualifier), these qualifiers
    enable you to override any operand-element masking that might be
    associated with that instruction.

    The /TMASK qualifier applies the EXAMINE command only to the
    elements of the register or array that correspond to the set
    bits (bit value: 1) of the mask. The /FMASK qualifier applies the
    EXAMINE command only to the elements that correspond to the clear
    bits (bit value: 0) of the mask. The current value of the vector
    length register (VLR) limits the highest register element that
    you can examine but not the highest array element.

    By default, if you do not specify a mask address expression with
    /TMASK or /FMASK, the vector mask register (VMR) is used. That
    is, the EXAMINE command is applied only to the elements of the
    vector register or array that correspond to the set bits (in the
    case of /TMASK) or clear bits (in the case of /FMASK) of VMR.

    If you specify a mask address expression with /TMASK or /FMASK,
    the value at that address is used as the mask, subject to the
    following conventions:

    o  You must use parentheses around the address expression.

    o  The number of mask elements limits the number of register or
       array elements that you can examine.

    o  If the mask address expression denotes a Boolean array, its
       values are used as the mask, in the same basic way that VMR is
       used in the default case.

    o  If the mask address expression denotes a non-Boolean array,
       the least significant bit value of each array element is used
       as the mask for the corresponding element of the register or
       target array.

    o  If the mask address expression denotes a Boolean scalar type,
       its value is used as the mask for the first element of the
       register or target array. No other elements are examined.

    o  If the mask address expression denotes any other type, its
       least significant bit value is used as the mask for the first
       element of the register or target array. No other elements are
       examined.

    o  For a multi-element mask, the lowest specified element of
       the mask is applied to the lowest specified element of the
       register or target array.