Library /sys$common/syshlp/dbg$help.hlb DEBUG, Language Support, Pascal, Additional Information  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    In general, you can examine, evaluate, and deposit into
    variables, record fields, and array components. An exception
    to this occurs under the following circumstances: if a variable
    is not referenced in a program, the Pascal compiler might not
    allocate the variable. If the variable is not allocated and you
    try to examine it or deposit into it, you will receive an error
    message.

    When you deposit data into a variable, the debugger truncates
    the high-order bits if the value being deposited is larger than
    the variable; the debugger fills the high-order bits with zeros
    if the value being deposited is smaller than the variable. If
    the deposit violates the rules of assignment compatibility, the
    debugger displays an informational message.

    You can examine and deposit into automatic variables (within any
    active block); however, because automatic variables are allocated
    in stack storage and are contained in registers, their values
    are considered undefined until the variables are initialized or
    assigned a value.